ISO 18405:2017 水中音響 — 用語 | ページ 6

3.1.1.1

音

弾性媒体中の弾性応力の作用を介して伝達される圧力，応力又は材料変位の変化で，媒体の局所的な圧縮及び膨張，又はそのような伝達された変化の重ね合わせを伴うもの。

注記 1音が存在する媒体は，しばしば適切な形容詞によって示される。

注記 2:このドキュメントの残りの部分では、媒体は圧縮性流体であると想定されています。

注記3音波は音の実現である。

注記4 「音」という言葉は複合名詞の一部として使用されることもあり，その場合は「音響」の同義語である。例えば、「音響圧力」と「音響パワー」は、 音圧（3.1.2.1） と 音響パワー（3.1.3.14） の同義語です。

[出典: 参考文献 [23] および参考文献 [35]]

3.1.1.2

環境音

特定の活動がない場合に存在する 音（3.1.1.1）

注記1:環境音は場所固有であり、時間固有である。

注記2特定の活動がない場合、すべての音は環境音である。

注記 3:環境音には 環境雑音が含まれる (3.1.5.11) 。

注記4特定活動の例としては、水中の音を測定する行為及び特定の音源による音の放射が挙げられる。

注記 5:周囲の音は、人為的 (例: 船積み) または自然 (例: 風、生物相) である可能性があります。

3.1.1.3

サウンドスケープ

<水中音響> 空間的、時間的、周波数的属性、および音場に寄与する音源の種類に関する 周囲音の特徴付け (3.1.1.2)

3.1.1.4

残響

散乱体の集合体又はアンサンブルによる音の累積的な散乱から生じる 音（3.1.1.1） 。

注記 1:残響は通常、体積内または表面上の散乱体から発生します。

3.1.1.5

物質的な要素

音の粒子

媒質の平均密度を表す媒質の最小要素

注記1:この要素の特徴的な長さスケールは，分子の平均自由行程の数倍のオーダーである(参考文献[22]を参照)

3.1.2.1

音圧

p

音の作用によって生じる全圧への寄与 (3.1.1.1)

注記 1:音圧は時間の関数であり、引数tによってp ( t ) のように表すことができます。ここで、 pは音圧、 tは時間です。

注記2:音圧はパスカル(Pa)で表される。

注記 3: 「音圧」という用語は、「二乗平均平方根音圧」の同義語として使用されることがあります。この使用は非推奨です。

注記4 「音圧」という用語は，IEC 60050 によってp ( t ) の二乗平均平方根値として定義されている。この IEC 定義は現在の (ISO) 定義と互換性がありませんが、ISO 規格のユーザーは、IEC によって開発された水中聴音器校正規格などで IEC 定義に遭遇する可能性があります。

注記 5:加重音圧は 3.7.1.1 で定義されています。

[出典:ISO 80000‑8:2007, 8-9.1 および 8-9.2, 修正]

3.1.2.2

音圧スペクトル

P

音圧のフーリエ変換 (3.1.2.1)

注記 1:音圧スペクトルは周波数の関数であり、 P ( f ) のように、引数fによって示される場合があります。ここで、 Pは音圧スペクトルであり、 fは周波数です。

注記2公式形式では、 P ( f ) d f . ISO 80000-2:2009 を参照してください。

注記 3:音圧スペクトルは、ヘルツあたりのパスカル (Pa/Hz) の単位で表されます。

注記4一般に、 P ( f ) は周波数の複素関数です。

注記5音圧pの定義は、単一イベントまたはf的な音P号にtされます。 ) は、信号の開始前と終了後に常にゼロに設定されます。また、連続音圧信号の有限セグメントに適用することもできます。この場合、セグメントの開始時刻と終了時刻を指定する必要があります。

3.1.2.3

ゼロからピークまでの音圧

ピーク音圧

p_0-pk

p_pk

指定された周波数範囲について、指定された時間間隔中の 音圧（3.1.2.1） の最大の大きさ。

注記1:ゼロからピークまでの音圧はパスカル(Pa)で表される。

注記 2:ゼロからピークまでの音圧は、正または負の音圧から発生する可能性があります。

[出典:ISO/TR 25417:2007, 2.4, 修正]

3.1.2.4

圧縮圧力

p_c

音圧 (3.1.2.1) 、 p ( t )、 p ( t ) > 0 の場合、 tは時間

注記1圧縮圧力はパスカル(Pa)で表される。

注記2：衝撃波の場合、圧縮圧力は「爆発過圧」と呼ばれることがあります。参考文献 [33] を参照してください。

3.1.2.5

ピーク圧縮圧力

p_pk,c

指定された周波数範囲について、指定された時間間隔中の最大 圧縮圧力（3.1.2.4）

注記 1ピーク圧縮圧力はパスカル (Pa) で表される。

注記 2:ピーク圧縮圧力は、正の音圧からのみ発生する可能性があります。

注記 3:衝撃波の場合、最大圧縮圧力は「最大爆風過圧」と呼ばれることがあります。

3.1.2.6

まれな派閥圧力

p_r

| 音圧の大きさ (3.1.2.1) | p ( t ) |、 p ( t ) < 0 の場合、 pは音圧、 tは時間

注記1:希薄圧力はパスカル(Pa)で表される。

3.1.2.7

ピークレア派閥圧力

p_pk,r

指定された周波数範囲について、指定された時間間隔中の最大 希薄圧力 (3.1.2.6)

注記 1:ピーク レア ファクション プレッシャーはパスカル (Pa) で表されます。

注記 2:ピーク希薄圧は、負の音圧からのみ発生する可能性があります。

注記 3:レア陣営の圧力のピークは常にプラスです。

3.1.2.8

ピーク間音圧

p_pk-pk

指定された周波数範囲について、指定された時間間隔中の ピーク圧縮圧力（3.1.2.5） と ピーク希薄圧力（3.1.2.7） の合計。

注記 1ピーク ツー ピーク音圧はパスカル (Pa) で表されます。

注記 2ピーク圧縮圧力の時間間隔を決定するために使用される開始時間と終了時間は、ピーク希薄圧力の時間間隔を決定するために使用される時間と同じでなければならない。

3.1.2.9

音の粒子の変位

δ

音（3.1.1.1） の作用によって引き起こされる 材料要素（3.1.1.5） の変位。

注記1:音粒子の変位は時間tの関数であり、 δ ( t )のように引数tによって示される。

注記2音響粒子変位はメートル(m)で表される。

注記 3音響粒子の変位はベクトル量である。音粒子の変位の空間成分は、記号に下付き文字を割り当てることによって示すことができます。たとえば、デカルト座標では、 δ = ( δ _x 、 δ _y 、 δ _z ) です。水中音響の慣習により、通常、 z軸は海面から垂直に下向きに選択され、 x軸とy軸は水平面にあります。

[出典:ISO 80000‑8:2007, 8-10, 修正]

3.1.2.10

音速

u

音（3.1.1.1） の作用によって生じる 物質要素（3.1.1.5） の速度への寄与。

注記 1音の粒子速度は時間tの関数であり、 u ( t ) のように、引数tによって示すことができます。

注記 3:音の粒子速度は、メートル/秒 (m/s) の単位で表されます。

注記4音の粒子速度はベクトル量である．音の粒子速度の空間成分は、記号に下付き文字を割り当てることによって示すことができます。たとえば、デカルト座標では、 u = ( u _x , u _y , _z ) です。水中音響の慣習により、通常、 z軸は海面から垂直に下向きに選択され、 x軸とy軸は水平面にあります。

[出典:ISO 80000‑8:2007, 8-11, 修正]

3.1.2.11

音の粒子の加速

a

音（3.1.1.1） の作用によって引き起こされる 物質要素（3.1.1.5） の加速への寄与。

注記 1音粒子の加速度は時間tの関数であり、 a ( t ) のように、引数tによって示すことができます。

注記3音の粒子の加速度は，メートル毎秒2乗(m/s ² )の単位で表される。

注記4音粒子の加速度はベクトル量である．音粒子の加速度の空間成分は、記号に下付き文字を割り当てることによって示すことができます。たとえば、デカルト座標では、 a = ( a _x , a _y , a _z ) です。水中音響の慣習により、通常、 z軸は海面から垂直に下向きに選択され、 x軸とy軸は水平面にあります。

[出典:ISO 80000‑8:2007, 8-12, 修正]

3.3.1.1

音響遠方場

吸収損失を補正したダイレクトパス電界振幅が範囲に反比例して変化する、均一媒体内の空間領域。

注記1:音響遠方界では、音圧と音粒子速度は実質的に同相である。

注記2一般的な技術的慣行は、音源の最大寸法の2乗を音響波長で割った値のπ倍以上である音源からの距離を遠距離場領域として識別することです。

注記 3:範囲はすべて、発信元と受信先の間の特定の直接経路に沿って取得されます。

注記 4:射程距離への逆依存は、光源がすべての方向に等しく放射することを意味するものではありません。

注記 5:参考文献 [30] を参照。

3.3.1.2

ファーフィールド音圧

音源の 音響遠方場（3.3.1.1） における 音圧（3.1.2.1） 。

3.3.1.3

音響センター

自由音場条件下で， 音響遠方場（3.3.1.1） で発信波面が発散するように見える点。

注記1音響中心の位置は一般に周波数に依存する。

注記2:指向性音源は、一般に、放射場の各球面調和成分 (単極子、双極子など) ごとに異なる音響中心を持っています。別の定義では、各放射方向を 2 つの音響中心 (1 つは振幅用、もう 1 つは位相用) に割り当てます。

[出典: 参照[35]]

3.3.1.4

ソース波形

s

音源の 音響中心 (3.3.1.3) からの指定された方向の距離rと遅延 遠方音圧 (3.3.1.2) p ( t−t₀ + r/ c ) の積。指定された時間原点t₀が、音源の位置にある実際の媒質と同じ密度と音速cを持ち、すべての音響的に活性な表面が実際の音源と同じ動きをする仮想的な無限一様無損失媒質に置かれた場合実際の媒体で

注記 1:ソース波形は時間の関数であり、 s ( t ) のように、引数tによって示される場合があります。ここで、 sはソース波形、 tは時間です。

注記2式の形式では、 s ( t−t₀ ) = rp ( t−t₀ + r/ c )この式にt₀ = r/ cを代入し、 pを再配置すると、より一般的な式p ( t ) = s ( t−r/ c )/ rが得られます。

注記 3:ソース波形は、パスカル メートル (Pa m) の単位で表されます。

注記 4:遅延時間t−t₀ + r/ cで遠方音圧を評価すると、音源波形が音響遠方場の正確な距離rに依存しないことが保証されます。

注記 5:仮想媒体はすべての方向に制限されていません。

注記6ソナー投射器などの指向性音源の場合，特に明記しない限り，方向は主軸の方向である。

注記7音源波形の数値は、パスカルメートル単位で表した場合、仮想的な点モノポール音源から1mの距離に存在する音圧に等しく、パスカルで表した場合、音源波形が定義されているのと同じ架空の無限一様無損失媒体内で、仮想点音源の音源波形が指定された方向の真の音源波形と等しい場合。このため、この仮想的な音圧をソース波形の代替測定基準として使用するのが一般的です。この代替測定基準は通常、「マイクロパスカル アット 1 メートル」の単位で引用され、しばしば「μPa @ 1 m」と省略されます。圧力として、この代替メトリックの正しい単位はパスカル (Pa) またはマイクロパスカル (μPa) です。仮想点モノポール ソースのプロパティは、指定された方向によって異なります。

3.3.1.5

音響暴露源係数

エネルギー源係数

_E、F

音源の 音響中心（3.3.1.3） からの特定の方向の距離の 2 乗r²と、 音響遠方場（3.3.1.1） における 時間積分された音圧の 2 乗 （3.1.3.5）の積その距離E _p ( r ) での音源の、すべての音響的に活性な表面の同一の動きで、音源の位置にある実際の媒質と同じ密度と音速の仮想無限一様無損失媒質に配置された場合真の媒体における真の情報源として

1 年生から入学まで:式の形式では、 F_S,E = r²E _p ( r ) です。

注記2エネルギー源係数は、パスカル平方メートル平方秒(Pa ² m ² s)の単位で表される。

注記3周波数範囲を指定しなければならない。

注記 4エネルギー源係数の値は距離rとは無関係である。

注記 5:エネルギー源係数は、一時的な音源の特性です。

注記6露光の積分時間は、受信パルスの全持続時間です。

注記7この用語の名前における「エネルギー」の使用は、時間積分された2乗音圧に比例する量を意味する。

注記8仮想媒質はすべての方向に無限である。

注記9ソナー投射器などの指向性音源の場合、特に明記しない限り、方向は主軸の方向である。

注記10エネルギー源係数の値を変更することなく、音響中心以外の音源内の点からの距離を指定することができます。

注記11エネルギー源係数の数値は、パスカル平方メートル平方秒の単位で表される場合、仮想の点モノポール音源から1mの距離に存在する時間積分された音圧の2乗に等しい、パスカルの二乗の単位で表される場合、エネルギー源係数が定義されている同じ仮想無限一様無損失媒体に配置され、仮想点源のエネルギー源係数が真のエネルギー源係数のエネルギー源係数と等しい場合指定された方向。このため、エネルギー源係数の代替測定基準として、この仮想的な時間積分音圧の 2 乗を使用するのが一般的です。この代替測定基準は通常、「1 メートルにおけるマイクロパスカル平方秒」の単位で引用され、しばしば「μPa ² s @ 1 m」と略されます。時間積分された 2 乗圧力として、この代替メトリックの正しい単位は、パスカル 2 乗秒 (Pa ² s) またはマイクロパスカル 2 乗秒 (μPa ² s) です。仮想点モノポール ソースのプロパティは、指定された方向によって異なります。

注記12音源の周囲の実媒質は，この媒質の 特性音響インピーダンス（3.1.5.6） が音源の周囲の位置に依存しないという意味で，局所的に一様であると仮定される。

3.3.1.6

ソースファクター

F_S

音源の 音響中心 (3.3.1.3) からの特定の方向の距離の 2 乗r²と 音響遠方場 (3.3.1.1) における 平均二乗音圧 (3.1.3.1) の積。その距離、 音源の、音源の位置で実際の媒質と同じ密度と音速の仮想的な無限一様無損失媒質に置かれ、真の媒質内の真の音源とすべての音響的にアクティブな表面の同一の動きがある場合

1 年生から入学まで:式の形式では、 F_S = r² （ r ）。

注記2ソース係数は、パスカル平方メートル平方 (Pa ² m ² ) の単位で表されます。

注記3時間間隔と周波数範囲を指定する。

注記 4ソース係数の値は距離rとは無関係である。

注記 5:音源係数は、統計的に静止した音源の特性です。

注記6仮想媒質はすべての方向に無限である。

注記7音源係数の値を変更することなく，音源内の音響中心以外の点からの距離を指定することができる。

注記8ソナー投射器などの指向性音源の場合，特に明記しない限り，方向は主軸の方向である。

注記9音源係数の平方根の数値は、パスカルメートルの単位で表される場合、仮想の点モノポールから1mの距離に存在する二乗平均音圧に等しい。線源係数が定義されているのと同じ架空の無限一様無損失媒体に置かれ、仮想点源の線源係数が指定された方向の真の線源係数と等しい場合、線源をパスカルで表す場合。このため、この仮説上の二乗平均音圧を音源要因の代替測定基準として使用するのが一般的です。この代替測定基準は通常、「マイクロパスカル アット 1 メートル」の単位で引用され、しばしば「μPa @ 1 m」と省略されます。圧力として、この代替メトリックの正しい単位はパスカル (Pa) またはマイクロパスカル (μPa) です。仮想点モノポール ソースのプロパティは、指定された方向によって異なります。

注記10：音源の周囲の実媒質は、この媒質の 特性音響インピーダンス（3.1.5.6） が音源の周囲の位置に依存しないという意味で、局所的に一様であると仮定される。

3.3.1.7

表面影響ソース波形

遠方場署名

s '

音源の 音響中心 (3.3.1.3) とその海面反射像からの特定方向の距離rと遅延 遠方音圧 (3.3.1.2) の積p ( t − t₀ + r/ c )、指定された時間原点t₀に対して、音源の位置にある実際の媒体と同じ密度と音速cを持つ仮想的な半無限の均一な損失のない媒体に置かれ、同じ動きをする場合実際の媒体内の実際の音源としてのすべての音響的に活性な表面の、 tは時間

注記 1:表面影響源の波形は時間の関数であり、引数tによってs ′( t ) のように表すことができます。ここで、 s ′ は表面影響源の波形であり、 tは時間です。

注記2式の形式では， s ′( t − t₀ ) = rp ( t − t₀ + r/ c ) である．この式にt₀ = r/ cを代入し、 pを再配置すると、よりなじみのある式p ( t ) = s ′( t − r/ c )/ rが得られます。

注記 3:表面影響源の波形は、パスカル メートル (Pa m) の単位で表されます。

注記 4遅延時間t − t₀ + r/ cで遠方音圧を評価するr 、表面に影響を受けた音源波形が 音響遠方場 (3.3 .1.1) .

注記5:音響中心は海面上または海面に近い点である。

注記6:表面に影響を受けたソース波形は、仰角の関数です。また、方位角の関数にすることもできます。

注記7海面の存在は、音響遠方界が2つの寄与の和であることを意味する: 直接経路と表面反射経路. 表面反射経路からの寄与, 時々「ゴースト」と呼ばれる」は通常、海面でπ位相シフトを受けると想定されています。

注記8：海面の存在は、発生源の挙動に影響を与える可能性があります。

注記 9:海面反射で完全な鏡面反射が発生するように、表面影響音源波形の概念は低周波音に有効です。典型的な基準は、音響波数と二乗平均表面波高の積が 1 よりはるかに小さいことです。

注記10時間と範囲の起源は明確に述べられるべきである。

注記 11:同義語の「遠方場の特徴」は、反射地震学に使用される音源を特徴付けるために最も一般的に使用されます。

3.3.1.8

ソーススペクトル

S

ソース波形のフーリエ変換 (3.3.1.4)

注記1:ソーススペクトルは周波数の関数であり、 S ( f ) のように、引数fによって示される場合があります。ここで、 Sはソーススペクトルであり、 fは周波数です。

注記2公式形式では、 S ( f ) d f . ISO 80000-2 を参照してください。

注記 3ソーススペクトルは、ヘルツあたりのパスカルメートル (Pa m/Hz) の単位で表されます。

注記 4一般に、 S ( f ) は周波数の複素関数です。

注記5ヘルツあたりのパスカルメートルの単位で表される音源スペクトルの数値は、仮想的な点モノポール音源から1mの距離に存在する 音圧スペクトル(3.1.2.2) に等しい。 、パスカルで表した場合、ソーススペクトルが定義されているのと同じ仮想無限一様無損失媒体に配置され、仮想点ソースのソーススペクトルが指定された方向の真のソーススペクトルのソーススペクトルと等しい場合。このため、この仮想的な音圧スペクトルをソース スペクトルの代替測定基準として使用するのが一般的です。この代替測定基準は通常、「1 メートルでヘルツあたりのマイクロパスカル」の単位で引用され、しばしば「μPa/Hz @ 1 m」と略されます。圧力スペクトルとして、この代替メトリックの正しい単位は、ヘルツあたりのパスカル (Pa/Hz) またはヘルツあたりのマイクロパスカル (μPa/Hz) です。仮想点モノポール ソースのプロパティは、指定された方向によって異なります。

注記 6:震源スペクトルは反射地震学で使用されます。

3.3.1.9

表面影響光源スペクトル

S '

表面影響源波形のフーリエ変換 (3.3.1.7)

注記1:表面影響源スペクトルは周波数の関数であり、 S ′( f )のように、引数fによって示される場合があります。ここで、 S ′は表面影響源スペクトルであり、 fは周波数です。

注記2公式形式では、 S '( f ) d f . ISO 80000-2 を参照してください。

注記 3:表面影響源スペクトルは、パスカル メートル/ヘルツ (Pa m/Hz) の単位で表されます。

注記4:表面に影響を受けた光源スペクトルは仰角に依存する.また、方位角にも依存する可能性があります。

注記 5:海面反射で完全な鏡面反射が発生するように、表面影響音源スペクトルの概念は低周波音に有効です。典型的な基準は、音響波数と二乗平均表面波高の積が 1 よりはるかに小さいことです。

注記6一般に， S ′( f ) は周波数の複素関数である．

3.5.1.1

分析信号

q

実部が 信号 (3.1.5.8) p ( t ) に等しく、虚部がp ( t ) のヒルベルト変換に等しい複素量

注記 1解析信号は時間の関数であり、 q ( t ) のように、引数tによって示される場合があります。ここで、 qは解析信号であり、 tは時間です。

注記2式の形式では、信号p ( t ) の解析信号q ( t ) は、 q ( t ) = p ( t ) + i h ( t ) で与えられます。ここで、 h ( t ) はp ( t ) のヒルベルト変換です。

注記3信号p ( t ) が 音圧 (3.1.2.1) の場合，解析信号はパスカル (Pa) で表される。

3.5.1.2

複雑なエンベロープ

µ

解析信号 (3.5.1.1) q ( t ) の積、および定数 -2πi, 一定周波数f₀ 、および時間tの積の指数関数

注記1:複素エンベロープは時間の関数であり、 μ ( t ) のように、引数tによって示される場合があります。ここで、 μは複素エンベロープであり、 tは時間です。

注記2公式形式では、 .

注記 3q ( t ) が 音圧の解析信号 (3.1.2.1) である場合，複素包絡線はパスカル (Pa) で表される。

注記4狭帯域信号の場合、量f₀は通常、その信号の中心周波数です。

3.5.1.3

有効信号持続時間

| の時間に関する積分の 2 乗μ ( t )| | の時間に関する積分で割った²μ ( t )|ここで、 μ ( t ) は 音圧 (3.1.2.1) ^の 複素エンベロープ (3.5.1.2) です。

1年生から入学まで：式の形で、 .

注記2有効信号持続時間は秒単位で表される。

注記3有効信号持続時間は過渡信号の特性である。

注記4複素エンベロープの大きさは 解析信号の大きさに等しい(3.5.1.1) 。

[出典: 参照[24]]

3.5.1.4

閾値超過信号持続時間

_{yデシベル}

平均二乗音圧レベル (3.2.1.1) (SPL) が指定されたしきい値を超え、最大 SPL からyデシベルだけ下回っている時間。

注記1閾値超過信号の持続時間は秒単位で表される。

注記 2:各方向に複数のしきい値交差がある場合、SPL が増加する最初の交差と SPL が減少する最後の交差の間の時間間隔を選択することにより、しきい値超過信号の持続時間が明確になります。

注記3閾値超過信号の持続時間は，過渡信号の特性である。

[ソース: 参照 [32], 変更]

3.5.1.5

パーセンテージ エネルギー信号持続時間

τ _×%

全エネルギーの (50 −x/2) % で始まり (50 + x/2) % で終わる、 時間積分された音圧の 2 乗 (3.1.3.5) の指定されたパーセンテージxが発生する時間

注記1エネルギー信号持続時間のパーセンテージは秒単位で表される。

注記2エネルギー信号持続時間のパーセンテージは過渡信号の特性である。

[ソース: 参照 [32], 変更]

3.5.1.6

実効信号帯域幅

ν_eff

| の周波数に関する積分の 2 乗M ( f )| ²の周波数に関する積分で除算 | M ( f )|ここで、 M ( f ) は 複素エンベロープ (3.5.1.2) μ ( t ) のフーリエ変換であり、時間依存のフィールド量p ( t ) に対応し^ます。

1年生から入学まで：式の形で、 ここで、 M ( f ) は複素エンベロープμ ( t ) のフーリエ変換 (ISO 80000-2 を参照) です。

注記2実効信号帯域幅はヘルツ(Hz)で表される。

[出典: 参照[24]]

3.6.1.1

ソナー信号の音圧

ターゲットの存在によって生じる特定の位置での 音圧（3.1.2.1） 。

注記 1:指定された位置は通常、水中聴音器であり、ソナー受信アレイの一部を形成する場合があります。

3.6.1.2

ソナー信号電圧

ソナー信号の音圧（3.6.1.1） によって引き起こされる、指定された周波数帯域のソナー受信機での電圧。

注記1：デジタル受信機システムでは、電圧は元の電圧のデジタル表現に変換される場合があります。この状況では、この定義の「電圧」という言葉は、「同等のアナログ受信機システムで生成されたであろう電圧」と解釈されます。

3.6.1.3

ターゲットエコー

アクティブなソナー送信から発生し、その後ターゲットによって再放射されるソナー受信機での 音（3.1.1.1） 。

注記1：アクティブソナーの場合、ターゲットエコーは ソナー信号の音圧（3.6.1.1） と同義語です。

3.6.1.4

ソナー残響

<アクティブソナー> ターゲットエコー（3.6.1.3） を除くアクティブソナー送信から発信されたソナー受信機での 音（3.1.1.1 ）

注記 1:ソナー残響は、例えば、環境内の無数の不均一性による累積的な散乱によって引き起こされます。

3.6.1.5

バックグラウンド ノイズ

音響ノイズ

周囲雑音（3.1.5.11） 、 音響自己雑音（3.1.5.10） 、および該当する場合は ソナー残響（3.6.1.4） の組み合わせ

注記1: バックグラウンドノイズ(3.6.1.5) の概念は測定システムで使用される。

注記 2:測定システムにアクティブ送信機 (アクティブ ソナーやエアガン アレイなど) が含まれる場合、バックグラウンド ノイズは、周囲ノイズ、音響自己ノイズ、およびソナー残響の組み合わせです。

注記3:測定システムがアクティブ送信機を含まない場合(例えば、パッシブソナーまたは聴力検査)、背景雑音は周囲雑音と音響自己雑音の組み合わせです。

3.6.1.6

非音響自己雑音

音圧入力がない場合のソナー受信機出力の電圧変動

注記1：デジタル受信機システムでは、電圧は元の電圧のデジタル表現に変換される場合があります。この状況では、この定義の「電圧」という言葉は、「同等のアナログ受信機システムで生成されたであろう電圧」と解釈されます。

3.6.1.7

セルフノイズ

音響自己雑音（3.1.5.10） と 非音響自己雑音（3.6.1.6） の組み合わせによって引き起こされる電圧の変動。

注記1：デジタル受信機システムでは、電圧は元の電圧のデジタル表現に変換される場合があります。この状況では、この定義の「電圧」という言葉は、「同等のアナログ受信機システムで生成されたであろう電圧」と解釈されます。

3.6.1.8

ソナーノイズ電圧

バックグラウンドノイズ（3.6.1.5） と 非音響自己ノイズ（3.6.1.6） の組み合わせによって生じる、特定の周波数帯域のソナー受信機での電圧。

注記1：デジタル受信機システムでは、電圧は元の電圧のデジタル表現に変換される場合があります。この状況では、この定義の「電圧」という言葉は、「同等のアナログ受信機システムで生成されたであろう電圧」と解釈されます。

3.6.1.9

ソナー信号対雑音比

SNR

R _sn

受信機処理チェーンの特定の点における平均二乗 ソナー信号電圧（3.6.1.2） と平均二乗 ソナー雑音電圧（3.6.1.8） の比。

注記 1:指定できる処理チェーンのポイントには、ビームフォーマへの入力およびビームフォーマからの出力が含まれますが、これらに限定されません。

注記2ソナーノイズ電圧の周波数帯域は、ソナー信号電圧の周波数帯域と同じでなければならない。

注記3ソナー信号対雑音比と関連用語との関係を図1に要約する。

図 1 —ソナー信号対雑音比と関連用語の関係¹

3.6.1.10

検出確率

p_d

1 回の観測で 1 つの (そして 1 つだけの) 信号が存在する場合に、 信号 (3.1.5.8) の存在決定を行う確率

3.6.1.11

誤警報の確率

p_fa

1 回の観測で、信号が存在しない場合に 信号 (3.1.5.8) を提示する決定を下す確率

3.6.1.12

ノイズ検出器出力

ソナー信号が入力にないときの検出器の出力

3.6.1.13

信号とノイズ検出器の出力

ソナー信号が入力に存在するときの検出器の出力

3.6.1.14

検出指数

d

指定された検出器について、平均 信号に雑音検出器の出力を加え たもの（3.6.1.13）と 雑音検出器の出力 の平均（3.6.1.12）との差の二乗と雑音検出器の出力の分散との比。

注記1: 検出指数(3.7.2.14)も 参照のこと。

[出典: リファレンス[39], p382]

3.6.1.15

等価平均二乗ソナー ノイズ音圧

p_、式²

ハイドロフォン出力での平均二乗 ソナーノイズ電圧 (3.6.1.8) V_N²を自由音場開放回路ハイドロフォン電圧感度M _p²で割った値

注記1式の形式では、 p_N,eq² = V_N²/ M _p² .

注記 2等価平均二乗ソナー騒音音圧は、パスカル二乗 (Pa ² ) の単位で表されます。

注記3 ソナー雑音電圧(3.6.1.8) の周波数帯域を規定すること。

注記4自由音場開回路水中聴音器の電圧感度は、IEC 60500によって定義されています。

3.1.3.1

mean-square sound pressure

integral over a specified time interval of squared sound pressure (3.1.2.1) , divided by the duration of the time interval, for a specified frequency range

Note 1 to entry: In formula form, , where p(t) is the sound pressure, and t₁ and t₂ are the start and end times, respectively. For a transient sound, the start and end times are sometimes chosen to correspond to the start and end of the percentage energy signal duration (3.5.1.5) .

Note 2 to entry: Mean-square sound pressure is expressed in units of pascal squared (Pa²).

Note 3 to entry: The square root of the mean-square sound pressure is a field quantity known as the root-mean-square sound pressure. This field quantity may be denoted p_rms.

3.1.3.2

mean-square sound particle displacement

integral over a specified time interval of squared magnitude of the sound particle displacement (3.1.2.9) , divided by the duration of the time interval, for a specified frequency range

Note 1 to entry: In formula form, , where δ(t) is the magnitude of the sound particle displacement, and t₁ and t₂ are the start and end times, respectively.

Note 2 to entry: Mean-square sound particle displacement is expressed in units of metre squared (m²).

Note 3 to entry: The square root of the mean-square sound displacement is a field quantity known as the root-mean-square sound displacement. This field quantity may be denoted δ_rms.

3.1.3.3

mean-square sound particle velocity

integral over a specified time interval of squared magnitude of the sound particle velocity (3.1.2.10) , divided by the duration of the time interval, for a specified frequency range

Note 1 to entry: In formula form, , where u(t) is the magnitude of the sound particle velocity, and t₁ and t₂ are the start and end times, respectively.

Note 2 to entry: Mean-square sound particle velocity is expressed in units of (metre per second) squared [(m/s)²].

Note 3 to entry: The square root of the mean-square sound velocity is a field quantity known as the root-mean-square sound velocity. This field quantity may be denoted u_rms.

3.1.3.4

mean-square sound particle acceleration

integral over a specified time interval of squared magnitude of the sound particle acceleration (3.1.2.11) , divided by the duration of the time interval, for a specified frequency range

Note 1 to entry: In formula form, , where a(t) is the magnitude of the sound particle acceleration, and t₁ and t₂ are the start and end times, respectively.

Note 2 to entry: Mean-square sound particle acceleration is expressed in units of (metre per second squared) squared [(m/s²)²].

Note 3 to entry: The square root of the mean-square sound acceleration is a field quantity known as the root-mean-square sound acceleration. This field quantity may be denoted a_rms.

3.1.3.5

time-integrated squared sound pressure

sound pressure exposure

sound exposure

E_p,T

<underwater acoustics> integral of the square of the sound pressure (3.1.2.1) , p, over a specified time interval or event, for a specified frequency range

Note 1 to entry: In formula form, , where t₁ and t₂ are the start and end times of the time interval or event, respectively, and T = t₂ – t₁ is the duration of the signal.

Note 2 to entry: Time-integrated squared sound pressure is expressed in units of pascal squared second (Pa² s).

Note 3 to entry: According to the continuous form of Parseval’s theorem (also known as Plancherel’s theorem), the time-integrated squared sound pressure can be written as the frequency-integrated sound exposure spectral density (3.1.3.9) . In formula form, , where p_T (t) is equal to p(t) for t₁ < t < t₂ and is otherwise zero, P(f) is the Fourier transform (see ISO 80000-2) of p_T (t) and E_f is the sound exposure spectral density of the pressure time series p_T (t).

Note 4 to entry: In the far field the time-integrated squared sound pressure is equal to the product of the characteristic acoustic impedance (3.1.5.6) of the medium and the magnitude of the time-integrated sound intensity (3.1.3.10) . In the near field this equality does not hold in general.

Note 5 to entry: See also weighted time-integrated squared sound pressure (3.7.1.2) .

3.1.3.6

time-integrated squared sound particle displacement

E_δ,T

integral of the square of the magnitude of the sound particle displacement (3.1.2.9) , δ, over a specified time interval or event, for a specified frequency range

Note 1 to entry: In formula form, , where t₁ and t₂ are the start and end times of the time interval or event, respectively, and T = t₂ – t₁ is the duration of the signal.

Note 2 to entry: Time-integrated squared sound particle displacement is expressed in units of metre squared second (m² s).

3.1.3.7

time-integrated squared sound particle velocity

E_u,T

integral of the square of the magnitude of the sound particle velocity (3.1.2.10) , u, over a specified time interval or event, for a specified frequency range

Note 1 to entry: In formula form, , where t₁ and t₂ are the start and end times of the time interval or event, respectively, and T = t₂ – t₁ is the duration of the signal.

Note 2 to entry: Time-integrated squared sound particle velocity is expressed in units of (metre per second) squared second [(m/s)² s].

3.1.3.8

time-integrated squared sound particle acceleration

E_a,T

integral of the square of the magnitude of the sound particle acceleration (3.1.2.11) , a, over a specified time interval or event, for a specified frequency range

Note 1 to entry: In formula form, , where t₁ and t₂ are the start and end times of the time interval or event, respectively, and T = t₂ – t₁ is the duration of the signal.

Note 2 to entry: Time-integrated squared sound particle acceleration is expressed in units of (metre per second squared) squared second [(m/s²)² s].

3.1.3.9

sound exposure spectral density

sound pressure exposure spectral density

E_f

<underwater acoustics> distribution as a function of non-negative frequency of the time-integrated squared sound pressure (3.1.3.5) per unit bandwidth of a sound having a continuous spectrum

Note 1 to entry: Sound exposure spectral density is expressed in units of pascal squared second per hertz (Pa² s/Hz).

Note 2 to entry: In its idealized form, sound exposure spectral density is evaluated as the limit, as the bandwidth tends to zero, of the time-integrated squared sound pressure in a finite frequency band divided by the frequency bandwidth.

Note 3 to entry: For operational purposes, sound exposure spectral density is estimated as the time-integrated squared sound pressure in a finite frequency band divided by the frequency bandwidth. The result is equal to the mean value of the sound exposure spectral density, averaged across the band. The time duration and frequency band shall be specified.

Note 4 to entry: According to the continuous form of Parseval’s theorem (also known as Plancherel’s theorem), the sound pressure spectrum (3.1.2.2) , P(f), is related to the sound pressure p(t) via the formula . It follows from these formulae that for any positive non-zero frequency, E_f (f) = 2|P(f)|². For zero frequency, E_f (0) = |P(0)|².

Note 5 to entry: The integral over positive frequencies of the sound exposure spectral density is equal to the time-integrated squared sound pressure .

3.1.3.10

sound intensity

instantaneous sound intensity

I

product of the sound pressure (3.1.2.1) , p, and the sound particle velocity (3.1.2.10) , u

Note 1 to entry: Sound intensity is a function of time, t, which may be indicated by means of an argument t, as in I (t).

Note 2 to entry: In formula form, I (t) = p(t) u (t).

Note 3 to entry: Sound intensity is expressed in units of watt per metre squared (W/m²).

Note 4 to entry: Sound intensity is a vector quantity. Spatial components of the sound intensity may be indicated by assigning subscripts to the symbol. For example, in Cartesian coordinates, I = (I_x , I_y , I_z ). By convention in underwater acoustics, the z axis is usually chosen to point vertically down from the sea surface, with x and y axes in the horizontal plane.

Note 5 to entry: Sound intensity is also known as the “Umov vector”, “Poynting vector” or “Umov-Poynting vector”.

Note 6 to entry: Sound pressure is a real scalar quantity and sound particle velocity is a real vector quantity. Sound intensity is therefore a real vector quantity.

Note 7 to entry: In the International System of Quantities (ISQ), sound pressure and sound particle velocity are instantaneous quantities. Their product, sound intensity, is therefore also an instantaneous quantity in the ISQ. The upper case symbol I , without a subscript, is used to denote this instantaneous quantity to distinguish it from the time-averaged sound intensity, I _av.

Note 8 to entry: The term “sound intensity” is in widespread use as a synonym of “time-averaged sound intensity”, I _av. This use is not compatible with the ISQ.

Note 9 to entry: This definition could become inapplicable in situations with a high mean fluid flow.

Note 10 to entry: This definition is in accordance with ISO 80000-8:2007, 8-17.1.

[SOURCE:ISO/TR 25417:2007, 2.12, modified]

3.1.3.11

time-averaged sound intensity

I _av

integral over a specified time interval of sound intensity (3.1.3.10) , I , divided by the duration of the time interval, for a specified frequency range

Note 1 to entry: In formula form, , where t₁ and t₂ are the start and end times, respectively.

Note 2 to entry: Time-averaged sound intensity is expressed in units of watt per metre squared (W/m²).

Note 3 to entry: Time-averaged sound intensity is a vector quantity. Spatial components of the time-averaged sound intensity may be indicated by assigning subscripts to the symbol. For example, in Cartesian coordinates, I _av = (I_av,x , I_av,y , I_av,z ). By convention in underwater acoustics, the z axis is usually chosen to point vertically down from the sea surface, with x and y axes in the horizontal plane.

Note 4 to entry: This definition is in accordance with ISO 80000-8:2007, 8.

[SOURCE:ISO/TR 25417:2007, 2.13, modified]

3.1.3.12

equivalent plane wave sound intensity

I_eq

mean-square sound pressure (3.1.3.1) , , divided by the product of the density, ρ, and sound speed, c, of the undisturbed fluid

Note 1 to entry: In formula form, .

Note 2 to entry: Equivalent plane wave sound intensity is expressed in units of watt per metre squared (W/m²).

Note 3 to entry: The averaging time and frequency band shall be specified.

Note 4 to entry: The equivalent plane wave sound intensity is a scalar quantity, equal to the component of time-averaged sound intensity (3.1.3.11) in the direction of propagation of a plane progressive sound wave having the specified mean-square sound pressure.

3.1.3.13

mean-square sound pressure spectral density

distribution as a function of non-negative frequency of the mean-square sound pressure (3.1.3.1) per unit bandwidth of a sound having a continuous spectrum

Note 1 to entry: Mean-square sound pressure spectral density is expressed in units of pascal squared per hertz (Pa²/Hz).

Note 2 to entry: In its idealized form, mean-square sound pressure spectral density is evaluated as the limit, as the bandwidth tends to zero, of the mean-square sound pressure in a finite frequency band divided by the frequency bandwidth.

Note 3 to entry: For operational purposes, mean-square sound pressure spectral density is estimated as the mean-square sound pressure in a finite frequency band divided by the frequency bandwidth. The averaging time and frequency band shall be specified.

Note 4 to entry: According to the continuous form of Parseval’s theorem (also known as Plancherel’s theorem), the sound pressure spectrum (3.1.2.2) , P(f), is related to the sound pressure, p(t), via the formula .

Note 5 to entry: As a consequence of the Wiener-Khinchin theorem, the mean-square sound pressure spectral density of a sound pressure signal is also equal to twice the Fourier transform (see ISO 80000-2) of the autocorrelation function of that signal.

Note 6 to entry: Mean-square sound pressure spectral density is one of several related quantities known generically as “power spectral density”. The generic term is used with a descriptor (in this case, mean-square sound pressure) to indicate the type of power-like quantity whose spectral density is being described.

3.1.3.14

sound power

W

integral over a specified surface of the product of the sound pressure (3.1.2.1) , p, and the component of the sound particle velocity (3.1.2.10) in the direction normal to that surface, u_n

Note 1 to entry: Sound power is a function of time, t, which may be indicated by means of an argument t, as in W(t).

Note 2 to entry: Sound power is expressed in watts (W).

Note 3 to entry: This definition could become inapplicable in situations with a high mean fluid flow.

[SOURCE:ISO 80000‑8:2007, 8-16, modified]

3.1.3.15

time-averaged sound power

W_av

integral over a specified time interval of sound power (3.1.3.14) , W, divided by the duration of the time interval, for a specified frequency range

Note 1 to entry: If the surface completely encloses a sound source, and in the absence of absorption, the time-averaged sound power is equal to the average rate per unit time at which sound energy is radiated from the source.

3.1.4.1

one-third octave

one-third octave (base 2)

one third of an octave

Note 1 to entry: The frequency ratio corresponding to a one-third octave is 2^1/3, or approximately 1,259 9.

Note 2 to entry: One-third octave (base 2) bands are defined in ISO 13261-1.

Note 3 to entry: From the definition 1 oct ≡ log₂(2) = 1 (see ISO 80000-8:2007, 8-3.a), it follows that one one-third octave (base 2) (1/3 oct) is equal to 1/3, or approximately 0,333 33.

[SOURCE:DIN 13320]

3.1.4.2

one-third octave (base 10)

decidecade

ddec

one tenth of a decade

Note 1 to entry: The frequency ratio corresponding to a decidecade (1 ddec) is 10^0,1, or approximately 1,258 9, which is smaller than a one-third octave (base 2) by approximately 0,08 %.

Note 2 to entry: The use of “one-third octave” to mean 1 ddec is permitted by IEC 61260-1 and ANSI/ASA S1.6-2016.

Note 3 to entry: From the definition 1 dec ≡ log₂(10) (see ISO 80000-8:2007, 8-3 b), it follows that one decidecade (0,1 dec) is equal to 0,1 log₂(10), or approximately 0,332 19.

Note 4 to entry: The symbol for one-third octave (base 10) is ddec. This symbol is not intended to be used as an abbreviation.

3.1.5.1

force impulse

J_F

integral of a transient force, over a specified time interval or event, for a specified frequency range

Note 1 to entry: In formula form, J_F = , where F (t) is the force, and the integral is taken either over the entire time-history, or between specified limits (as in the second integral above).

Note 2 to entry: Force impulse is expressed in units of newton second (N s).

Note 3 to entry: Force impulse is a vector quantity. Spatial components of the force impulse may be indicated by assigning subscripts to the symbol. For example, in Cartesian coordinates, J_F = (J_F,x , J_F,y , J_F,z ). By convention in underwater acoustics, the z axis is usually chosen to point vertically down from the sea surface, with x and y axes in the horizontal plane.

Note 4 to entry: The force impulse vector represents the total momentum transferred by the force during that time.

[SOURCE: Reference [35]]

3.1.5.2

pressure impulse

J_p

integral of a transient sound pressure (3.1.2.1) , p(t), over a specified time interval or event, for a specified frequency range

Note 1 to entry: In formula form, , where the integral is taken either over the entire time-history, or between specified limits (as in the second integral above).

Note 2 to entry: Pressure impulse is expressed in units of pascal second (Pa s).

Note 3 to entry: If the sound pressure is non-negative over the entire interval of integration, the pressure impulse is referred to as “positive-pressure impulse”.

Note 4 to entry: If the sound pressure is non-positive over the entire interval of integration, the magnitude of the pressure impulse is referred to as “negative-pressure impulse”.

Note 5 to entry: Pressure impulse is a scalar quantity.

Note 6 to entry: See also force impulse (3.1.5.1) .

3.1.5.3

sound pressure variance

μ₂

variance of the sound pressure (3.1.2.1) , p(t), over a specified time interval, t₁tot₂, for a specified frequency range

Note 1 to entry: In formula form, is the mean sound pressure in the same time interval.

Note 2 to entry: Sound pressure variance is expressed in units of pascal squared (Pa²).

Note 3 to entry: If the mean sound pressure is zero, the sound pressure variance is equal to the mean-square sound pressure.

3.1.5.4

sound pressure skewness

γ₁

skewness of the sound pressure (3.1.2.1) , p(t), over a specified time interval, t₁tot₂, for a specified frequency range

Note 1 to entry: In formula form, are the sound pressure variance (3.1.5.3) and mean sound pressure, respectively, in the same time interval.

3.1.5.5

sound pressure kurtosis

β

kurtosis of the sound pressure, p(t), over a specified time interval, t₁tot₂, for a specified frequency range

Note 1 to entry: In formula form, are the sound pressure variance (3.1.5.3) and mean sound pressure, respectively, in the same time interval.

Note 2 to entry: See Reference [28].

3.1.5.6

characteristic acoustic impedance

characteristic specific acoustic impedance

Z_c

sound pressure (3.1.2.1) divided by the component of the sound particle velocity (3.1.2.10) in the direction of the wave propagation, at a point in a non-dissipative medium and for a plane progressive wave

Note 1 to entry: In a fluid of density, ρ, and speed of sound, c, the characteristic acoustic impedance is equal to the product, ρc.

Note 2 to entry: Characteristic acoustic impedance is expressed in units of pascal second per metre (Pa s/m).

[SOURCE:ISO 80000‑8:2007, 8-19, modified]

3.1.5.7

specific acoustic impedance

z

Fourier transform of sound pressure (3.1.2.1) , P(f), divided by the Fourier transform of sound particle velocity (3.1.2.10) in a given direction, U(f)

Note 1 to entry: In formula form, z(f) = P(f)/U(f) = P(f) U*(f)/[U(f) U*(f)].

Note 2 to entry: Specific acoustic impedance is expressed in units of pascal second per metre (Pa s/m).

Note 3 to entry: See IEC 60050 (IEV 801–25–13) and ISO 80000-2:2009, 2-18.1, Fourier transform.

Note 4 to entry: Specific acoustic impedance can also be defined as the complex sound pressure, .

Note 5 to entry: Specific acoustic impedance is a complex quantity whose magnitude equals the sound pressure amplitude divided by the amplitude of a given sound particle velocity component, and whose phase equals the sound pressure phase minus the phase of the given sound particle velocity component.

3.1.5.8

signal

specified time-varying electric current, voltage, sound pressure (3.1.2.1) , sound particle displacement (3.1.2.9) , or other field quantity of interest

3.1.5.9

noise

time-varying electric current, voltage, sound pressure (3.1.2.1) , sound particle displacement (3.1.2.9) , or other field quantity except the signal (3.1.5.8) or signals

3.1.5.10

acoustic self-noise

sound (3.1.1.1) at a receiver caused by the deployment, operation, or recovery of a specified receiver, and its associated platform

3.1.5.11

ambient noise

sound (3.1.1.1) except acoustic self-noise (3.1.5.10) and except sound associated with a specified signal (3.1.5.8)

Note 1 to entry: In the absence of a specified signal, ambient noise is all sound except acoustic self-noise.

Note 2 to entry: An example of a specified signal might be the echo from a sonar target.

3.2.1.1

mean-square sound pressure level

root-mean-square sound pressure level

sound pressure level

SPL

L_p,rms

L_p

DEPRECATED:mean-square SPL

ten times the logarithm to the base 10 of the ratio of the mean-square sound pressure (3.1.3.1) to the specified reference value, p₀², in decibels

Note 1 to entry: Mean-square sound pressure level is the level of the power quantity equal to the mean-square sound pressure, denoted /p₀²) dB.

Note 2 to entry: Mean-square sound pressure level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of mean-square sound pressure, p₀², is 1 μPa². The reference value shall be specified.

Note 4 to entry: The averaging time and frequency range shall be specified.

Note 5 to entry: Mean-square sound pressure level can be written as the level of the field quantity root-mean-square sound pressure, i.e. L_p = 20 log₁₀( /p₀) dB. The reference value of sound pressure is p₀ = 1 μPa.

Note 6 to entry: The abbreviation “mean-square SPL” is deprecated because in normal use of English this would mean “mean-square value of SPL”, the meaning of which differs from the intended one, “level of the mean-square sound pressure”.

Note 7 to entry: Weighted sound pressure level is defined in 3.7.

3.2.1.2

mean-square sound particle displacement level

root-mean-square sound particle displacement level

sound particle displacement level

SDL

L_δ,rms

L_δ

ten times the logarithm to the base 10 of the ratio of the mean-square sound particle displacement (3.1.3.2) to the specified reference value, δ₀², in decibels

Note 1 to entry: Mean-square sound particle displacement level is the level of the power quantity equal to the mean-square magnitude of the sound particle displacement, denoted /δ₀²) dB.

Note 2 to entry: Mean-square sound particle displacement level is expressed in decibels (dB).

Note 3 to entry: The reference value of mean-square sound particle displacement, δ₀², is 1 pm². The reference value shall be specified.

Note 4 to entry: The averaging time and frequency range shall be specified.

3.2.1.3

mean-square sound particle velocity level

root-mean-square sound particle velocity level

sound particle velocity level

SVL

L_u,rms

L_u

ten times the logarithm to the base 10 of the ratio of the mean-square sound particle velocity (3.1.3.3) to the specified reference value, u₀², in decibels

Note 1 to entry: Mean-square sound particle velocity level is the level of the power quantity equal to the mean-square magnitude of the sound particle velocity, denoted /u₀²) dB.

Note 2 to entry: Mean-square sound particle velocity level is expressed in decibels (dB).

Note 3 to entry: The reference value of mean-square sound particle velocity, u₀², is 1 (nm/s)². The reference value shall be specified.

Note 4 to entry: The averaging time and frequency range shall be specified.

[SOURCE:ANSI/ASA S1.1-2013, 3.23, modified]

3.2.1.4

mean-square sound particle acceleration level

root-mean-square sound particle acceleration level

sound particle acceleration level

SAL

L_a

ten times the logarithm to the base 10 of the ratio of the mean-square sound particle acceleration (3.1.3.4) to the specified reference value, a₀², in decibels

Note 1 to entry: Mean-square sound particle acceleration level is the level of the power quantity equal to the mean-square magnitude of the sound particle acceleration, denoted /a₀²) dB.

Note 2 to entry: Mean-square sound particle acceleration level is expressed in decibels (dB).

Note 3 to entry: The reference value of mean-square sound particle acceleration, a₀², is 1 μm²/s⁴. The reference value shall be specified.

Note 4 to entry: The averaging time and frequency range shall be specified.

3.2.1.5

time-integrated squared sound pressure level

sound exposure level

sound pressure exposure level

SEL

L_E,p

<underwater acoustics> ten times the logarithm to the base 10 of the ratio of the time-integrated squared sound pressure (3.1.3.5) , E_p , to the specified reference value, E_p,0, in decibels

Note 1 to entry: Time-integrated squared sound pressure level is the level of the power quantity time-integrated squared sound pressure, denoted E_p . In formula form, L_E,p = 10 log₁₀(E_p/E_p,0) dB.

Note 2 to entry: Time-integrated squared sound pressure level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of time-integrated squared sound pressure, E_p,0, is 1 μPa² s. The reference value shall be specified.

Note 4 to entry: The time duration and frequency range shall be specified.

Note 5 to entry: This definition is in accordance with ISO 80000-8:2007, 8.

Note 6 to entry: In air acoustics, the sound exposure level may be a weighted quantity (see ISO/TR 25417).

3.2.1.6

time-integrated squared sound particle displacement level

L_E,δ

ten times the logarithm to the base 10 of the ratio of the time-integrated squared sound particle displacement (3.1.3.6) , E_δ to the specified reference value, E_δ,0, in decibels

Note 1 to entry: Time-integrated squared sound particle displacement level is the level of the power quantity time-integrated squared sound particle displacement, denoted E_δ . In formula form, L_E,δ = 10 log₁₀(E_δ/E_δ,0) dB.

Note 2 to entry: Time-integrated squared sound particle displacement level is expressed in decibels (dB).

Note 3 to entry: The reference value of time-integrated squared sound particle displacement, E_δ,0, is 1 pm² s. The reference value shall be specified.

Note 4 to entry: The time duration and frequency range shall be specified.

3.2.1.7

time-integrated squared sound particle velocity level

L_E,u

ten times the logarithm to the base 10 of the ratio of the time-integrated squared sound particle velocity (3.1.3.7) , E_u , to the specified reference value, E_u,0, in decibels

Note 1 to entry: Time-integrated squared sound particle velocity level is the level of the power quantity time-integrated squared sound particle velocity, denoted E_u . In formula form, L_E,u = 10 log₁₀(E_u/E_u,0) dB.

Note 2 to entry: Time-integrated squared sound particle velocity level is expressed in decibels (dB).

Note 3 to entry: The reference value of time-integrated squared sound particle velocity, E_u,0, is 1 (nm/s)² s. The reference value shall be specified.

Note 4 to entry: The time duration and frequency range shall be specified.

3.2.1.8

time-integrated squared sound particle acceleration level

L_E,a

ten times the logarithm to the base 10 of the ratio of the time-integrated squared sound particle acceleration (3.1.3.8) , E_a , to the specified reference value, E_a,0, in decibels

Note 1 to entry: Time-integrated squared sound particle acceleration level is the level of the power quantity time-integrated squared sound particle acceleration, denoted E_a . In formula form, L_E,a = 10 log₁₀(E_a/E_a,0) dB.

Note 2 to entry: Time-integrated squared sound particle acceleration level is expressed in decibels (dB).

Note 3 to entry: The reference value of time-integrated squared sound particle acceleration, E_a,0, is 1 (μm/s²)² s. The reference value shall be specified.

Note 4 to entry: The time duration and frequency range shall be specified.

3.2.1.9

sound exposure spectral density level

L_E,f

ten times the logarithm to the base 10 of the ratio of the sound exposure spectral density (3.1.3.9) , E_f , to the specified reference value, E_f,0, in decibels

Note 1 to entry: Sound exposure spectral density level is the level of the power quantity sound exposure spectral density, denoted E_f . In formula form, L_E,f = 10 log₁₀(E_f/E_f,0) dB.

Note 2 to entry: Sound exposure spectral density level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of sound exposure spectral density, E_f,0, is 1 μPa² s/Hz. The reference value shall be specified.

Note 4 to entry: If the operational form of the definition of sound exposure spectral density is used, the time duration and frequency range shall be specified.

3.2.1.10

mean-square sound pressure spectral density level

L_p,f

ten times the logarithm to the base 10 of the ratio of the mean-square sound pressure spectral density (3.1.3.13) , , in decibels

Note 1 to entry: Mean-square sound pressure spectral density level is the level of the power quantity mean-square sound pressure spectral density, denoted dB.

Note 2 to entry: Mean-square sound pressure spectral density level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of mean-square sound pressure spectral density, , is 1 μPa²/Hz. The reference value shall be specified.

Note 4 to entry: If the operational form of the definition of mean-square sound pressure spectral density is used, the averaging time and frequency range shall be specified.

3.2.2.1

zero-to-peak sound pressure level

peak sound pressure level

L_p,0-pk

L_p,pk

DEPRECATED:peak SPL

twenty times the logarithm to the base 10 of the ratio of the zero-to-peak sound pressure (3.1.2.3) , p_pk, to the specified reference value, p₀, in decibels

Note 1 to entry: Zero-to-peak sound pressure level is the level of the field quantity zero-to-peak sound pressure, denoted p_pk. In formula form, L_p,pk = 20 log₁₀(p_pk/p₀) dB.

Note 2 to entry: Zero-to-peak sound pressure level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of zero-to-peak sound pressure, p₀, is 1 μPa. The reference value shall be specified.

Note 4 to entry: The time interval and frequency range shall be specified.

Note 5 to entry: The abbreviation “peak SPL” is deprecated because in normal use of English, this would mean “peak value of SPL”, the meaning of which differs from the intended one, “level of the peak sound pressure”.

[SOURCE:ISO/TR 25417:2007, 2.5, modified]

3.2.2.2

peak compressional sound pressure level

L_p,pk,c

twenty times the logarithm to the base 10 of the ratio of the peak compressional sound pressure, p_pk,c, to the specified reference value, p₀, in decibels

Note 1 to entry: Peak compressional sound pressure level is the level of the field quantity peak compressional sound pressure, denoted p_pk,c. In formula form, L_p,pk,c = 20 log₁₀(p_pk,c/p₀) dB.

Note 2 to entry: Peak compressional sound pressure level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of peak compressional sound pressure, p₀, is 1 μPa. The reference value shall be specified.

Note 4 to entry: The time interval and frequency range shall be specified.

3.2.2.3

peak rarefactional sound pressure level

L_p,pk,r

twenty times the logarithm to the base 10 of the ratio of the peak rarefactional sound pressure, p_pk,r, to the specified reference value, p₀, in decibels

Note 1 to entry: Peak rarefactional sound pressure level is the level of the field quantity peak rarefactional sound pressure, denoted p_pk,r. In formula form, L_p,pk,r = 20 log₁₀(p_pk,r/p₀) dB.

Note 2 to entry: Peak rarefactional sound pressure level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of peak rarefactional sound pressure, p₀, is 1 μPa. The reference value shall be specified.

Note 4 to entry: The time interval and frequency range shall be specified.

3.3.2.1

source level

sl

L_S

ten times the logarithm to the base 10 of the ratio of the source factor (3.3.1.6) , F_S, to the specified reference value, F_S,0, in decibels

Note 1 to entry: Source level is the level of the power quantity source factor, denoted F_S. In formula form, L_S = 10log₁₀(F_S/F_S,0) dB, where F_S,0 = 1 μPa² m².

Note 2 to entry: Source level is expressed in decibels (dB).

Note 3 to entry: The source level in a specified direction is equal to the mean-square sound pressure level (3.2.1.1) at a distance of 1 m from a hypothetical point source, placed in the (hypothetical) infinite uniform lossless medium used to define the source factor, and with the same source factor for the specified direction as the true source. This equality has led to the widespread practice of citing source level with a reference value of “1 μPa @ 1 m”. According to this document, the reference value for source level is F_S,0 = 1 μPa² m². The reference value shall be specified.

Note 4 to entry: The time interval and frequency range shall be specified.

Note 5 to entry: Source level can be written as the level of the field quantity root source factor, i.e.
L_S = 20 log₁₀( ) dB. The reference value of root source factor is 1 μPa m.

Note 6 to entry: Source level is a property of a statistically stationary sound source.

Note 7 to entry: For a directional sound source such as a sonar projector, the direction is that of the principal axis unless stated otherwise.

Note 8 to entry: The source level can be determined by adding propagation loss (3.4.1.4) to the measured mean-square sound pressure level.

Note 9 to entry: Source level is a property of an underwater sound source that is determined by the motion of its moving surfaces. If sound is scattered from an otherwise passive underwater object, the “motion” referred to in the definition of source factor refers to the motion relative to that of the incident field, i.e. relative to the sound particle motion that would have existed in the absence of the scattering object. In the context of the active sonar equation (3.6.2.11) , the definition of “source level” applies to objects that scatter sound in this way. For a plane wave incident on the object from direction θ_i, whose mean-square sound pressure level is L_p , the source level in the direction θ_s is given by L_S(θ_s) = L_p (θ_i) + N_ts(θ_i, θ_s), where N_ts is the target strength (3.6.2.8) of the object.

3.3.2.2

sound exposure source level

energy source level

ESL

L_S,E

ten times the logarithm to the base 10 of the ratio of the sound exposure source factor (3.3.1.5) , F_S,E to the specified reference value, F_S,E,0, in decibels

Note 1 to entry: Sound exposure source level is the level of the power quantity sound exposure source factor, denoted, F_S,E . In formula form, L_S,E = 10 log₁₀(F_S,E/F_S,E,0) dB, where F_S,E,0 = 1 μPa² m² s.

Note 2 to entry: Sound exposure source level is expressed in decibels (dB).

Note 3 to entry: The sound exposure source level in a specified direction is equal to the time-integrated squared sound pressure level (3.2.1.5) at a distance of 1 m from a hypothetical point source, placed in the (hypothetical) infinite uniform lossless medium used to define the sound exposure source factor, and with the same sound exposure source factor for the specified direction as the true source. This equality has led to the widespread practice of citing source level with a reference value of “1 μPa² s @ 1 m”. According to this document, the reference value for source level is F_S,E,0 = 1 μPa² m² s. The reference value shall be specified.

Note 4 to entry: The frequency range shall be specified.

Note 5 to entry: Sound exposure source level is a property of a transient sound source.

Note 6 to entry: The integration time for the exposure is the entire duration of the received pulse.

Note 7 to entry: For a directional sound source such as a sonar projector, the direction is that of the principal axis unless stated otherwise.

Note 8 to entry: The sound exposure source level can be determined by adding sound exposure propagation loss (3.4.1.5) to the measured time-integrated squared sound pressure level.

Note 9 to entry: The use of “energy” in the name of this term implies the level of a quantity proportional to the time-integrated squared sound pressure (3.1.3.5) .

3.4.1.1

propagation factor

F_P

mean-square sound pressure (3.1.3.1) divided by the source factor (3.3.1.6) in a specified direction

Note 1 to entry: Propagation factor is expressed in units of reciprocal metre squared (m⁻²).

Note 2 to entry: Propagation factor is equal to m⁻², where N_pl is the propagation loss (3.4.1.4) .

Note 3 to entry: The time interval and frequency range shall be specified.

Note 4 to entry: Propagation factor applies to a statistically stationary sound source.

3.4.1.2

sound exposure propagation factor

energy propagation factor

F_E

time-integrated squared sound pressure (3.1.3.5) divided by the sound exposure source factor (3.3.1.5) in a specified direction

Note 1 to entry: Sound exposure propagation factor is expressed in units of reciprocal metre squared (m⁻²).

Note 2 to entry: Sound exposure propagation factor is equal to m⁻², where N_PL,E is the sound exposure propagation loss (3.4.1.5) .

Note 3 to entry: The frequency range shall be specified.

Note 4 to entry: The integration time for the exposure is the entire duration of the received pulse.

Note 5 to entry: Sound exposure propagation factor applies to a transient source.

Note 6 to entry: The use of “energy” in the name of this term implies a ratio of two quantities proportional to the time-integrated squared sound pressure.

3.4.1.3

transmission loss

tl

ΔL_tl

reduction in a specified level between two specified points x ₁, x ₂ that are within an underwater acoustic field

Note 1 to entry: In formula form, ΔL_tl = L( x ₁) – L( x ₂), where L( x ) is the specified level at position x . By convention, x ₁ is chosen to be closer to the source of sound than x ₂, such that transmission loss is usually a positive quantity.

Note 2 to entry: Transmission loss is expressed in decibels (dB).

Note 3 to entry: The averaging time and frequency range shall be specified.

Note 4 to entry: Examples of levels that might be specified include mean-square sound pressure level (3.2.1.1) and sound intensity level.

Note 5 to entry: The characteristic concerned (such as mean-square sound pressure level) shall be clearly identified because in all transmission systems more than one characteristic is propagated.

Note 6 to entry: The term “transmission loss” is sometimes used as a synonym of propagation loss (3.4.1.4) . This use is deprecated.

[SOURCE:ANSI/ASA S1.1-2013, 5.35, modified]

3.4.1.4

propagation loss

pl

N_pl

difference between source level (3.3.2.1) in a specified direction, L_S, and mean-square sound pressure level (3.2.1.1) , L_p ( x ), at a specified position, x

Note 1 to entry: In formula form, N_pl( x ) = L_S – L_p ( x ).

Note 2 to entry: Propagation loss is expressed in decibels (dB).

Note 3 to entry: The reference value for propagation loss is 1 m². The reference value shall be specified.

Note 4 to entry: The averaging time and frequency range shall be specified.

Note 5 to entry: Propagation loss applies to a statistically stationary sound source.

Note 6 to entry: Propagation loss is equal to 10log₁₀[F_P⁻¹/(1 m²)] dB, where F_P is the propagation factor (3.4.1.1) .

Note 7 to entry: The term “propagation loss” is sometimes used as a synonym of transmission loss (3.4.1.3) . This use is deprecated.

3.4.1.5

sound exposure propagation loss

energy propagation loss

EPL

N_PL,E

difference between sound exposure source level (3.3.2.2) in a specified direction, L_S,E , and time-integrated squared sound pressure level (3.2.1.5) , L_E,p ( x ), at a specified position, x

Note 1 to entry: In formula form, N_PL,E ( x ) = L_S,E – L_E,p ( x ).

Note 2 to entry: Sound exposure propagation loss is expressed in decibels (dB).

Note 3 to entry: The reference value for energy propagation loss, S_E,0/E₀, is 1 m². Here S_E,0 is the reference value of sound exposure source factor (3.3.1.5) and E₀ is the reference value of time-integrated squared sound pressure. The reference value of energy propagation loss shall be specified.

Note 4 to entry: The frequency range shall be specified.

Note 5 to entry: The integration time for the exposure is the entire duration of the received pulse.

Note 6 to entry: Sound exposure propagation loss applies to a transient sound source.

Note 7 to entry: Sound exposure propagation loss is equal to 10 log₁₀(F_E⁻¹/1 m²) dB, where F_E is the sound exposure propagation factor (3.4.1.2) .

3.4.2.1

differential scattering cross section

σ_Ω

quotient of the ensemble-average of the free-field time-averaged sound power (3.1.3.15) radiated per unit solid angle in a specified direction in the far field of the scattered field by the magnitude of the time-averaged sound intensity (3.1.3.11) of the incident field, for an incident plane wave and specified continuous incident signal

Note 1 to entry: Differential scattering cross section is expressed in units of metre squared per steradian (m²/sr).

Note 2 to entry: Differential scattering cross section is equal to the squared magnitude of the form function.

Note 3 to entry: Differential scattering cross section is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in σ_Ω (θ_i, ϕ_i; θ_s, ϕ_s).

Note 4 to entry: A related term, known as the “backscattering cross section”, is defined by some authors as σ_Ω,0 (see Reference [25]) and by others as .

3.4.2.2

total scattering cross section

σ_t

differential scattering cross section (3.4.2.1) , σ_Ω , of an object, integrated over all solid angles with respect to the scattering direction

Note 1 to entry: In formula form, σ_t(θ_i, ϕ_i) = , where θ_i and θ_s are incident and scattering elevation angles, and ϕ_i and ϕ_s the incident and scattering horizontal azimuthal angles, respectively. The integral is over all scattered solid angle elements dΩ_s.

Note 2 to entry: Total scattering cross section is expressed in units of metre squared (m²).

Note 3 to entry: Total scattering cross section depends on the incident elevation (θ_i) and horizontal azimuthal (ϕ_i) angles. This angle-dependence may be indicated by means of its arguments, as in σ_t(θ_i, ϕ_i).

[SOURCE:ANSI/ASA S1.1-2013, 5.49, modified]

3.4.2.3

absorption cross section

σ_a

quotient of the ensemble-average of the free-field time-averaged rate at which sound energy is converted to heat by the time-averaged sound intensity (3.1.3.11) of the incident field, for an incident plane wave

Note 1 to entry: Absorption cross section is expressed in units of metre squared (m²).

3.4.2.4

extinction cross section

σ_e

quotient of the mean rate of work done on a scatterer by the magnitude of the time-averaged sound intensity (3.1.3.11) of the incident field, for an incident plane wave

Note 1 to entry: Extinction cross section is expressed in units of metre squared (m²).

Note 2 to entry: The extinction cross section is equal to the sum of the total scattering cross section (3.4.2.2) and the absorption cross section (3.4.2.3) , i.e. σ_e = σ_t + σ_a.

3.4.2.5

volume differential scattering cross section per unit volume

σ_v

quotient of the ensemble-average of the free-field time-averaged sound power (3.1.3.15) radiated per unit solid angle in a specified direction in the far field of the scattered field per unit volume of water by the time-averaged sound intensity (3.1.3.11) of the incident field, for an incident plane wave

Note 1 to entry: Volume differential scattering cross section per unit volume is expressed in units of reciprocal metre reciprocal steradian (m⁻¹sr⁻¹).

Note 2 to entry: Volume differential scattering cross section per unit volume is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in σ_v (θ_i, ϕ_i; θ_s, ϕ_s).

3.4.2.6

sea surface differential scattering cross section per unit area

σ_s

ratio of the ensemble-average of the free-field time-averaged sound power (3.1.3.15) radiated per unit solid angle in a specified direction in the far field of the scattered field per unit area of sea surface to the time-averaged sound intensity (3.1.3.11) of the incident field, for an incident plane wave

Note 1 to entry: Sea surface differential scattering cross section per unit area is expressed in units of reciprocal steradian (sr⁻¹).

Note 2 to entry: Both the incident and scattered fields are understood to be in the water.

Note 3 to entry: Sea surface differential scattering cross section per unit area is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in σ_s (θ_i, ϕ_i; θ_s, ϕ_s).

3.4.2.7

sea bottom differential scattering cross section per unit area

σ_b

ratio of the ensemble-average of the free-field time-averaged sound power (3.1.3.15) radiated per unit solid angle in a specified direction in the far field of the scattered field per unit area of sea bottom to the time-averaged sound intensity (3.1.3.11) of the incident field, for an incident plane wave

Note 1 to entry: Sea bottom differential scattering cross section per unit area is expressed in units of reciprocal steradian (sr⁻¹).

Note 2 to entry: Both the incident and scattered fields are understood to be in the water.

Note 3 to entry: Sea bottom differential scattering cross section per unit area is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in σ_b (θ_i, ϕ_i; θ_s, ϕ_s).

3.4.2.8

volume scattering strength

S_v

ten times the logarithm to the base 10 of the ratio of the volume differential scattering cross section per unit volume (3.4.2.5) to the reference value, σ_v,0, in decibels

Note 1 to entry: In formula form, .

Note 2 to entry: Volume scattering strength is expressed in decibels (dB).

Note 3 to entry: The reference value of volume differential scattering cross section per unit volume is . The reference value shall be specified.

Note 4 to entry: Volume scattering strength is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in S_v (θ_i, ϕ_i; θ_s, ϕ_s).

3.4.2.9

sea surface scattering strength

S_s

ten times the logarithm to the base 10 of the ratio of the sea surface differential scattering cross section per unit area (3.4.2.6) to the reference value, σ_s,0, in decibels

Note 1 to entry: In formula form, .

Note 2 to entry: Sea surface scattering strength is expressed in decibels (dB).

Note 3 to entry: The reference value of sea surface differential scattering cross section per unit area is . The reference value shall be specified.

Note 4 to entry: Sea surface scattering strength is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in S_s (θ_i, ϕ_i; θ_s, ϕ_s).

3.4.2.10

sea bottom scattering strength

S_b

ten times the logarithm to the base 10 of the ratio of the sea bottom differential scattering cross section per unit area (3.4.2.7) to the reference value, σ_b,0, in decibels

Note 1 to entry: In formula form, .

Note 2 to entry: Sea bottom scattering strength is expressed in decibels (dB).

Note 3 to entry: The reference value of sea bottom differential scattering cross section per unit area is . The reference value shall be specified.

Note 4 to entry: Sea bottom scattering strength is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in S_b (θ_i, ϕ_i; θ_s, ϕ_s).

3.6.2.1

detection threshold

DT

ΔL_DT

ten times the logarithm to the base 10 of the sonar signal-to-noise ratio (3.6.1.9) of a signal (3.1.5.8) , R_SN,T, in decibels, for specified probability of detection (3.6.1.10) and probability of false alarm (3.6.1.11)

Note 1 to entry: In formula form, ΔL_DT = 10log₁₀R_SN,T dB.

Note 2 to entry: Detection threshold is expressed in decibels (dB).

Note 3 to entry: The specified probability of detection is often 0,5.

Note 4 to entry: When the sonar signal-to-noise ratio of a signal is equal to the detection threshold, that signal is referred to as being “just detectable”.

3.6.2.2

signal excess

ΔL_se

amount by which ten times the logarithm to the base 10 of the sonar signal-to-noise ratio (3.6.1.9) , R_sn, in decibels exceeds the detection threshold (3.6.2.1) , ΔL_DT

Note 1 to entry: In formula form, ΔL_se = 10log₁₀R_sn dB – ΔL_DT. The form of R_sn depends on the application.

Note 2 to entry: Signal excess is expressed in decibels (dB).

3.6.2.3

sonar equation

equation relating signal excess (3.6.2.2) (ΔL_se), sonar signal-to-noise ratio (3.6.1.9) (R_sn) and detection threshold (3.6.2.1) (ΔL_DT)

Note 1 to entry: According to this document, the terms of the sonar equation are levels or level differences, in decibels, representing ratios of mean-square sound pressure (3.1.3.1) . In principle, these ratios could be ratios of other power quantities such as equivalent plane wave sound intensity (3.1.3.12) , or mean-square sound particle velocity (3.1.3.3) , or their time-integrated equivalents.

Note 2 to entry: The sonar signal-to-noise ratio, R_sn, is usually related to the source level (3.3.2.1) , propagation loss (3.4.1.4) , noise level, etc., via the passive sonar equation (3.6.2.7) or active sonar equation (3.6.2.11) , often in the form ΔL_se = 10log₁₀R_sn dB – ΔL_DT.

Note 3 to entry: For passive sonar, R_sn can be determined by the formula 10log₁₀R_sn dB = L_S – N_pl – L_N + ΔL_PG. Substitution of this equation into the equation for signal excess gives the passive sonar equation in the form ΔL_se = L_S – N_pl – L_N + ΔL_PG – ΔL_DT.

Note 4 to entry: For active sonar, R_sn can be approximated by the formula 10log₁₀R_sn dB ≈ L_S – N_PL,Tx + N_ts – N_PL,Rx – L_N + ΔL_PG. Substitution of this approximation into the equation for signal excess gives the activesonarequation in the form ΔL_se ≈ L_S – N_PL,Tx + N_ts – N_PL,Rx – L_N + ΔL_PG – ΔL_DT.

Note 5 to entry: If in the active sonar equation, the target strength (3.6.2.8) (N_ts) is replaced with the equivalent target strength (3.6.2.10) (N_TS,eq), the equation becomes an exact one ΔL_se = L_S – N_PL,Tx + N_TS,eq – N_PL,Rx – L_N + ΔL_PG – ΔL_DT.

3.6.2.4

array gain

AG

ΔL_AG

ten times the logarithm to the base 10 of the ratio R_SN,out/R_SN,in, in decibels, where R_SN,in and R_SN,out are the sonar signal-to-noise ratio (3.6.1.9) at the input to and output from a beamformer of a sonar receiver, for a specified steer direction

Note 1 to entry: In formula form, ΔL_AG = 10 log₁₀(R_SN,out/R_SN,in) dB.

Note 2 to entry: Array gain is expressed in decibels (dB).

Note 3 to entry: This definition assumes the input sonar signal-to-noise ratio is the same for all input channels.

Note 4 to entry: For a plane wave sonar signal sound pressure (3.6.1.1) and isotropic background noise (3.6.1.5) , the array gain is referred to as the “directivity index”.

3.6.2.5

sonar noise level

L_N

ten times the logarithm to the base 10 of the ratio of the equivalent mean-square sonar noise sound pressure (3.6.1.15) , p_N,eq², for specified receiver-circuit impedance, to the specified reference value, p₀², in decibels

Note 1 to entry: Sonar noise level is the level of the power quantity equivalent mean-square sonar noise sound pressure, denoted p_N,eq². In formula form, L_N = 10 log₁₀(p_N,eq²/p₀²) dB.

Note 2 to entry: Sonar noise level is expressed in decibels (dB).

Note 3 to entry: The reference value of equivalent mean-square sonar noise sound pressure, p₀², is 1 μPa². The reference value shall be specified.

Note 4 to entry: The frequency band for the sonar noise voltage (3.6.1.8) shall be specified.

3.6.2.6

sonar processing gain

PG

ΔL_PG

ten times the logarithm to the base 10 of the ratio R_SN,out/R_SN,in, in decibels, where R_SN,in and R_SN,out are the sonar signal-to-noise ratios (3.6.1.9) at the hydrophone output and point in the receiver processing chain at which the detection decision is made, respectively

Note 1 to entry: In formula form, ΔL_PG = 10 log₁₀(R_SN,out/R_SN,in) dB.

Note 2 to entry: Sonar processing gain is expressed in decibels (dB).

Note 3 to entry: The frequency band for the sonar noise voltage (3.6.1.8) shall be specified.

Note 4 to entry: The detection decision is a choice between signal present and signal absent. See probability of detection (3.6.1.10) and probability of false alarm (3.6.1.11) .

Note 5 to entry: The gain from beamforming (i.e. array gain) is included in the sonar processing gain.

Note 6 to entry: The gain from time domain processing, such as a replica correlator, is included in the sonar processing gain.

Note 7 to entry: The gain from frequency domain processing, such as a pre-whitening filter, is included in the sonar processing gain.

Note 8 to entry: The sonar signal-to-noise ratio at the hydrophone output is the open circuit output signal-to-noise ratio.

3.6.2.7

passive sonar equation

sonar equation (3.6.2.3) for passive sonar obtained by relating sonar signal-to-noise ratio (3.6.1.9) (R_sn) to source level (3.3.2.1) (L_S), propagation loss (3.4.1.4) (N_pl), sonar noise level (3.6.2.5) (L_N) and sonar processing gain (3.6.2.6) (ΔL_PG) by means of the formula 10log₁₀R_sn dB = L_S – N_pl – L_N + ΔL_PG

Note 1 to entry: The passive sonar equation applies to the detection of sound from a continuous sound source.

Note 2 to entry: If the sonar processing includes a beamformer, the sonar processing gain includes the array gain (3.6.2.4) associated with that beamformer.

3.6.2.8

target strength

ts

N_ts

ten times the logarithm to the base 10 of the ratio of the target differential scattering cross section (3.4.2.1) , σ_Ω , to the specified reference value, σ_Ω,0, in decibels

Note 1 to entry: In formula form, , where θ_i, and θ_s are the incident and scattering elevation angles, and ϕ_i and ϕ_s the incident and scattering horizontal azimuthal angles, respectively.

Note 2 to entry: Target strength is expressed in decibels (dB).

Note 3 to entry: The reference value of differential scattering cross section is . The reference value shall be specified.

Note 4 to entry: Target strength is a bistatic quantity depending on the incident (θ_i) and scattering (θ_s) elevation angles and the incident (ϕ_i) and scattering (ϕ_s) horizontal azimuthal angles. This angle-dependence may be indicated by means of its arguments, as in may be referred to as the “monostatic target strength”.

Note 5 to entry: Target strength is a free-field quantity, defined in terms of an incident plane wave. It relates the mean-square sound pressure level (3.2.1.1) , L_p,s, of the scattered sound in the far field to the mean-square sound pressure level L_p,i of an incident plane wave. For an omnidirectional target in an infinite uniform lossless medium, the target strength is equal to L_p,s + 10log₁₀(r/r₀)² dB – L_p,i.

3.6.2.9

target echo level

el

L_te

mean-square sound pressure level (3.2.1.1) of the target echo (3.6.1.3)

Note 1 to entry: Target echo level is expressed in decibels (dB).

Note 2 to entry: In underwater acoustics, the reference value of mean-square sound pressure, p₀², is 1 μPa². The reference value shall be specified.

3.6.2.10

equivalent target strength

ts_eq

N_TS,eq

difference between sum of target echo level (3.6.2.9) (L_te), propagation loss (3.4.1.4) from sonar transmitter to target (N_PL,Tx), and propagation loss from target to sonar receiver (N_PL,Rx), and source level (3.3.2.1) (L_S)

Note 1 to entry: In formula form, N_TS,eq = L_te + N_PL,Tx + N_PL,Rx – L_S.

Note 2 to entry: Equivalent target strength is expressed in decibels (dB).

Note 3 to entry: The reference value for equivalent target strength, r₀², is 1 m². The reference value shall be specified.

Note 4 to entry: Equivalent target strength is applicable to both monostatic and bistatic sonar.

Note 5 to entry: For a target whose differential scattering cross section (3.4.2.1) is independent of both incident and scattering elevation angles, the equivalent target strength is equal to the target strength (see Reference [20], pp 607–610).

3.6.2.11

active sonar equation

sonar equation (3.6.2.3) for active sonar obtained by relating sonar signal-to-noise ratio (3.6.1.9) (R_sn) to the source level (3.3.2.1) of the sonar transmitter (L_S), propagation loss (3.4.1.4) from sonar transmitter to target (N_PL,Tx), equivalent target strength (3.6.2.10) (N_TS,eq), propagation loss from target to sonar receiver (N_PL,Rx), sonar noise level (3.6.2.5) (L_N) and sonar processing gain (3.6.2.6) (ΔL_PG) by means of the approximation 10 log₁₀R_sn dB, ≈ L_S – N_PL,Tx + N_TS,eq – N_PL,Rx – L_N + ΔL_PG

Note 1 to entry: For monostatic sonar, and for an omnidirectional source and omnidirectional target, N_PL,Tx and N_PL,Rx are related via the reciprocity principle. They are equal if the medium density at the target position, ρ_T, is equal to that at the sonar, ρ_S. More generally, they are related via the formula dB. See Reference [20], p.493.

Note 2 to entry: For the propagation loss from sonar transmitter to target, the source level is that of the sonar transmitter and the mean-square sound pressure level (3.2.1.1) is that at the target position in the absence of the target.

Note 3 to entry: For the propagation loss from target to sonar receiver, the source level is that of the target and the mean-square sound pressure level is the target echo level (3.6.2.9) . The source level of the target is equal to the sum of the equivalent target strength and the mean-square sound pressure level at the target position.

3.6.2.12

reverberation level

RL

L_R

ten times the logarithm to the base 10 of the ratio of the mean-square sound pressure (3.1.3.1) associated with sonar reverberation (3.6.1.4) , p_R², to the specified reference value, p₀², in decibels

Note 1 to entry: Reverberation level is the level of the power quantity equal to the mean-square sound pressure associated with sonar reverberation, denoted p_R². In formula form, L_R = 10 log₁₀(p_R²/p₀²) dB.

Note 2 to entry: Reverberation level is expressed in decibels (dB).

Note 3 to entry: The reference value of mean-square sound pressure, p₀², is 1 μPa². The reference value shall be specified.

Note 4 to entry: Reverberation level (L_R) is equal to the sonar noise level (3.6.2.5) (L_N) if there is no ambient noise (3.1.5.11) and no self-noise (3.6.1.7) .

3.6.2.13

reverberation-limited active sonar equation

sonar equation (3.6.2.3) for active sonar when ambient noise (3.1.5.11) and self-noise (3.6.1.7) are both negligible compared to sonar reverberation (3.6.1.4)

Note 1 to entry: In the reverberation-limited active sonar equation, sonar noise level (3.6.2.5) (L_N) is equal to reverberation level (3.6.2.12) (L_R).

3.7.1.1

weighted sound pressure

p_w

output of a specified linear filter when the input is the sound pressure (3.1.2.1) , p(t)

Note 1 to entry: Weighted sound pressure is a function of time, which may be indicated by means of an argument t, as in p_w(t), where p_w is weighted sound pressure and t is time.

Note 2 to entry: The weighted sound pressure is the convolution of the impulse response function h(t) of the filter and the sound pressure, p(t). In formula form, . The impulse response function is the inverse Fourier transform (see ISO 80000-2) of the sound pressure transfer function (3.7.1.5) , H(f). See ANSI S1.42.

Note 3 to entry: Weighted sound pressure is expressed in pascals (Pa).

Note 4 to entry: A filter is a process that removes from a signal some component or feature.

Note 5 to entry: The linear filter might be chosen to characterize a specified frequency-dependent characteristic of hearing sensitivity in a particular type of animal.

Note 6 to entry: The linear filter might be chosen to characterize a specified frequency-dependent transfer function of a mechanical or electrical system.

3.7.1.2

weighted time-integrated squared sound pressure

weighted sound pressure exposure

weighted sound exposure

E_p,w

integral of the square of the weighted sound pressure (3.7.1.1) , p_w, over a specified time interval or event

Note 1 to entry: In formula form, , where t₁ and t₂ are the start and end times, respectively.

Note 2 to entry: Weighted time-integrated squared sound pressure is expressed in units of pascal squared second (Pa² s).

Note 3 to entry: The integration time and frequency range shall be specified.

Note 4 to entry: According to the continuous form of Parseval’s theorem (also known as Plancherel’s theorem), the weighted sound exposure can be written as the frequency-integrated weighted sound exposure spectral density. In formula form, , where E_f is the sound exposure spectral density (3.1.3.9) (i.e. the spectral density of the unweighted sound exposure) and w(f) is the frequency weighting function (3.7.1.6) , given by w(f) = |H(f)|², where H(f) is the sound pressure transfer function (3.7.1.5) .

Note 5 to entry: If a specific frequency weighting function is applied, this should be indicated by appropriate subscripts.

3.7.1.3

mean-square weighted sound pressure level

weighted sound pressure level

SPL_w

L_p,w

ten times the logarithm to the base 10 of the ratio of the mean-square weighted sound pressure (3.7.1.1) to the specified reference value, p₀², in decibels

Note 1 to entry: Mean-square weighted sound pressure level is the level of the power quantity equal to the mean-square weighted sound pressure, denoted .

Note 2 to entry: Mean-square weighted sound pressure level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of mean-square weighted sound pressure, p₀², is 1 μPa². The reference value shall be specified.

Note 4 to entry: The averaging time and frequency range shall be specified.

Note 5 to entry: The type of weighting (e.g. frequency weighting or time weighting) shall be specified.

3.7.1.4

weighted sound exposure level

weighted sound pressure exposure level

SEL_w

L_E,p,w

ten times the logarithm to the base 10 of the ratio of the weighted time-integrated squared sound pressure (3.7.1.2) , E_p,w, to the specified reference value, E_p,0, in decibels

Note 1 to entry: Weighted sound exposure level is the level of the power quantity weighted time-integrated squared sound pressure, denoted E_p,w. In formula form, L_E,p,w = 10 log₁₀(E_p,w/E_p,0) dB.

Note 2 to entry: Weighted sound exposure level is expressed in decibels (dB).

Note 3 to entry: In underwater acoustics, the reference value of weighted time-integrated squared sound pressure, E_p,0, is 1 μPa² s. The reference value shall be specified.

Note 4 to entry: The integration time and frequency range shall be specified.

Note 5 to entry: If a specific frequency weighting is applied, this should be indicated by appropriate subscripts.

Note 6 to entry: This definition is in accordance with ISO 80000-8:2007, Clause 3.

Note 7 to entry: Integration time shall be specified.

[SOURCE:ISO/TR 25417:2007, 2.7, modified]

3.7.1.5

sound pressure transfer function

H

ratio of the Fourier transform of the weighted sound pressure (3.7.1.1) to the Fourier transform of the sound pressure (3.1.2.1)

Note 1 to entry: Sound pressure transfer function is a function of frequency, which may be indicated by means of an argument f, as in H(f), where H is the sound pressure transfer function and f is frequency.

Note 2 to entry: In formula form, H(f) = P_w(f)/P(f), where P_w(f) is the Fourier transform (see ISO 80000-2) of the weighted sound pressure and P(f) is the Fourier transform of the sound pressure.

3.7.1.6

frequency weighting function

w

squared magnitude of the sound pressure transfer function (3.7.1.5)

Note 1 to entry: Frequency weighting function is a function of frequency, which may be indicated by means of an argument f, as in w(f), where w is the frequency weighting function and f is frequency.

Note 2 to entry: In formula form, w(f) = |H(f)|², where H(f) is the sound pressure transfer function.

Note 3 to entry: The frequency weighting function is used in the calculation of spectrally weighted quantities when expressed as an integral over frequency using the continuous version of Parseval’s theorem (also known as Plancherel’s theorem). An example of a spectrally weighted quantity is the weighted time-integrated squared sound pressure (3.7.1.2) .

Note 4 to entry: Compare auditory frequency weighting function (3.7.1.7) .

3.7.1.7

auditory frequency weighting function

w_aud

frequency weighting function (3.7.1.6) chosen to represent a specified frequency-dependent characteristic of hearing sensitivity in a particular type of animal, by which an acoustic quantity is adjusted to reflect the importance of frequency dependence to that animal

Note 1 to entry: Auditory frequency weighting function is a function of frequency, which may be indicated by means of an argument f, as in w_aud(f), where w_aud is the auditory frequency weighting function and f is frequency.

Note 2 to entry: An example of auditory frequency weighting function for marine mammals is “M-weighting”. The auditory frequency weighting function corresponding to M-weighting is .

Note 3 to entry: Compare frequency weighting function.

3.7.2.1

behavioural hearing threshold

behavioural threshold of hearing

minimum level of a specified sound signal (3.1.5.8) that is capable of evoking a behaviourally measurable auditory sensation in a specified fraction of trials, for a specific subject and for specified conditions, including measurement geometry

Note 1 to entry: Behavioural hearing threshold is expressed in decibels (dB).

Note 2 to entry: The type of level, e.g. mean-square sound pressure level (3.2.1.1) or mean-square sound-particle velocity level, and its reference value shall be specified.

Note 3 to entry: As behavioural responses are sensitive to signal structure [e.g. tone pip, click, pure tone (see ANSI/ASA S3.20)], the characteristics of the signal and the manner in which it is presented to the subject shall be specified.

Note 4 to entry: The background noise (3.6.1.5) levels should be measured and reported.

Note 5 to entry: The behavioural hearing threshold is referred to as an “unmasked behavioural hearing threshold” if a decrease in the background noise does not result in a change to the behavioural hearing threshold.

Note 6 to entry: If the background noise is high enough to raise the behavioural hearing threshold above the unmasked behavioural hearing threshold, the behavioural hearing threshold is referred to as a “masked behavioural hearing threshold”.

Note 7 to entry: The method for threshold estimation shall be specified.

Note 8 to entry: The pure-tone behavioural hearing threshold measurement procedure prescribed in ISO 8253-1 recommends that the behavioural hearing threshold be defined as the lowest input level at which responses occur in at least 50 % of a series of ascending trials.

Note 9 to entry: The description of the measurement geometry and conditions shall be sufficient for the results to be duplicated. The geometry is especially important if the subject’s hearing is known or suspected to be sensitive to a quantity other than that being reported. For example, if a fish is sensitive to sound particle velocity (3.1.2.10) and its hearing threshold is reported in terms of sound pressure (3.1.2.1) , the information would need to be sufficiently detailed to permit the reconstruction of the sound field, with the same sound pressure and sound particle velocity at the fish location as in the original measurement.

3.7.2.2

electrophysiological hearing threshold

electrophysiological threshold of hearing

minimum level of a specified signal (3.1.5.8) that is capable of evoking a detectable and reproducible electrophysiological response, for a specific subject and for specified conditions, including measurement geometry

Note 1 to entry: Electrophysiological hearing threshold is expressed in decibels (dB).

Note 2 to entry: The type of level, e.g. mean-square sound pressure level (3.2.1.1) or mean-square sound-particle velocity level, and its reference value shall be specified.

Note 3 to entry: As electrophysiological responses are sensitive to signal structure [e.g. tone pip, click, pure tone (see ANSI/ASA S3.20)], the characteristics of the signal and the manner in which it is presented to the subject shall be specified.

Note 4 to entry: Both the background noise (3.6.1.5) and the background electrophysiological noise should be reported. Electrophysiological noise is the non-acoustic self-noise (3.6.1.6) consisting of myogenic and neurogenic sources plus any artefact caused by non-biological electrical interference.

Note 5 to entry: The electrophysiological hearing threshold is referred as an “unmasked electrophysiological hearing threshold” if a decrease in the background noise does not result in a change to the electrophysiological hearing threshold.

Note 6 to entry: If the background noise is high enough to raise the electrophysiological hearing threshold above the unmasked electrophysiological hearing threshold, the electrophysiological hearing threshold is referred to as a “masked electrophysiological hearing threshold”.

Note 7 to entry: Objective, statistically-based and subjective analyses can be used for detecting the presence of an electrophysiological response to an acoustic stimulus. Similarly, threshold estimation can be determined through various means, each of which carries with it associated errors and assumptions. The method for threshold estimation shall be specified.

Note 8 to entry: Electrophysiological hearing threshold estimates can be determined from different physiological processes (e.g. auditory brainstem response, cortical evoked responses and microphonic potentials), which characterize auditory processing at different levels of the auditory system. Electrophysiological methods are not equivalent to psychophysical procedures and electrophysiological hearing thresholds will differ from behavioural hearing thresholds (3.7.2.1) , which provide an integrated, whole organism response to signal detection.

Note 9 to entry: The description of the measurement geometry and conditions shall be sufficient for the results to be duplicated. The geometry is especially important if the subject’s hearing is known or suspected to be sensitive to a quantity other than that being reported. For example, if a fish is sensitive to sound particle velocity (3.1.2.10) and its hearing threshold is reported in terms of sound pressure, the information would need to be sufficiently detailed to permit the reconstruction of the sound field, with the same sound pressure and sound particle velocity at the fish location as in the original measurement.

3.7.2.3

audiogram

graph or table of behavioural hearing threshold (3.7.2.1) or electrophysiological hearing threshold (3.7.2.2) as a function of frequency

Note 1 to entry: Frequency is the centre frequency of the specified signal.

Note 2 to entry: It shall be stated whether the audiogram is for a behavioural hearing threshold or an electrophysiological hearing threshold.

[SOURCE:ANSI/ASA S3.20-2015, 4.01, modified]

3.7.2.4

auditory masking

auditory process by which the behavioural hearing threshold (3.7.2.1) or electrophysiological hearing threshold (3.7.2.2) for a sound (the signal) is raised by the presence of another sound (the noise)

Note 1 to entry: The masking phenomenon can also be related to thresholds of discrimination and recognition.

Note 2 to entry: The sound whose presence results in the raised threshold for detecting the signal is known as a “masking sound”. See ISO 8253-1:2010, 3.16.

3.7.2.5

auditory critical band

critical band

band of frequencies on either side of a specified frequency within which the presence of sound at a second frequency will interfere with the detection of sound at the specified frequency

Note 1 to entry: An auditory critical band can be defined for various measures of sound perception that involve frequency, including but not limited to audibility, loudness, and annoyance.

Note 2 to entry: In mammals, the auditory critical band is one of a number of contiguous bands of frequency into which the audio-frequency range may be notionally divided, such that sounds in different frequency bands are heard independently of one another, without mutual interference.

Note 3 to entry: The auditory critical band was originally examined by comparing the degree of masking of a pure tone by white noise (see ANSI/ASA S1.1–2013, 2.37) of progressively narrower bandwidth. It is also possible to demonstrate the critical band by comparing the degree of masking brought about by exposure to tones at different frequencies or to narrow bands of noise centred at different frequencies.

[SOURCE: Reference [35].]

3.7.2.6

auditory critical bandwidth

bandwidth of a specified auditory critical band (3.7.2.5)

Note 1 to entry: Auditory critical bandwidth is expressed in hertz (Hz).

3.7.2.7

critical ratio

cr

mean-square sound pressure (3.1.3.1) of the signal (3.1.5.8) divided by the mean-square sound pressure spectral density (3.1.3.13) of the noise (3.1.5.9) , for a just detectable pure tone signal masked by white noise

Note 1 to entry: Critical ratio is expressed in hertz (Hz).

Note 2 to entry: Critical ratio has dimensions of bandwidth. See Reference [40]. In Reference [31], it was postulated that when white noise (see ANSI/ASA S1.1–2013, 2.37) just masks a tone, the power of the noise in the auditory critical band (3.7.2.5) is equal to the power in the tone, in which case the critical ratio would be equal to the auditory critical bandwidth (3.7.2.6) . However, in Reference [40], it was showed that the critical ratio obtained from noise-masked tone studies, with both human and nonhuman animal subjects, is not a good indicator of critical bandwidth.

Note 3 to entry: The mean-square sound pressure spectral density, is the contribution to the mean-square sound pressure from a given frequency band, and δf is the bandwidth of that frequency band.

Note 4 to entry: Critical ratio can be defined in terms of sound particle velocity (3.1.3.7) instead of sound pressure.

Note 5 to entry: The duration of the tone signal is assumed to be sufficiently long for the hearing threshold to be independent of that duration.

3.7.2.8

critical signal-to-noise ratio level

critical ratio level

CRL

L_cr

ten times the logarithm to the base 10 of the ratio of the critical ratio (3.7.2.7) , R_c, to the specified reference value, (R_c)₀, in decibels

Note 1 to entry: In formula form, L_cr = 10log₁₀(R_c/ (R_c)₀) dB.

Note 2 to entry: Critical ratio level is expressed in decibels (dB).

Note 3 to entry: The reference value for critical ratio level, (R_c)₀, is 1 Hz. The reference value shall be specified.

Note 4 to entry: The critical ratio level is equal to the difference between the masked behavioural hearing threshold (3.7.2.1) at the tonal frequency and the mean-square sound pressure spectral density level (3.2.1.10) of the noise at the same frequency.

3.7.2.9

hearing threshold shift

threshold shift

change in the behavioural hearing threshold (3.7.2.1) or electrophysiological hearing threshold (3.7.2.2)

Note 1 to entry: Hearing threshold shift is expressed in decibels (dB).

Note 2 to entry: An increase in behavioural hearing threshold or electrophysiological hearing threshold corresponds to a decrease in hearing sensitivity.

[SOURCE:ANSI/ASA S3.20-2015, 4.63, modified]

3.7.2.10

permanent hearing threshold shift

permanent threshold shift

PTS

irreversible hearing threshold shift (3.7.2.9)

Note 1 to entry: Permanent hearing threshold shift is expressed in decibels (dB).

Note 2 to entry: Permanent hearing threshold shift can be caused by exposure to sound, through disease, through exposure to toxic substances, or as a result of ageing.

3.7.2.11

temporary hearing threshold shift

temporary threshold shift

TTS _t

TTS

reversible hearing threshold shift (3.7.2.9) , for a specified fatiguing stimulus

Note 1 to entry: Temporary hearing threshold shift is expressed in decibels (dB).

Note 2 to entry: Temporary hearing threshold shift can be superimposed on a permanent hearing threshold shift (3.7.2.10) .

Note 3 to entry: A measurement of temporary hearing threshold shift implies a measurement of (behavioural or electrophysiological) hearing threshold before exposure to a fatiguing stimulus (T₀) and at a specified time, t, after the exposure ceases (T_t ), and for a specified frequency. The temporary hearing threshold shift varies as a function of time after exposure and is equal to T_t minus T₀. It is commonly designated as TTS _t .

Note 4 to entry: The background noise (3.6.1.5) for both hearing threshold measurements is reported. If the hearing thresholds are masked by the background noise, this is indicated by referring to the measurement as a masked temporary hearing threshold shift.

Note 5 to entry: An elevation in the hearing threshold caused by masking is not a temporary hearing threshold shift.

[SOURCE:ANSI/ASA S3.20-2015, 4.64, modified]

3.7.2.12

loudness

perceived strength of sound (3.1.1.1)

Note 1 to entry: Loudness is the perceptual correlate of sound amplitude.

[SOURCE:ISO/IEC 23004‑2:2007, 4.97, modified.]

3.7.2.13

loudness level

sound pressure level of a given sound (3.1.1.1) whose loudness (3.7.2.12) is judged to be equal to that of a reference sound consisting of a frontally incident, sinusoidal plane progressive wave at a specified frequency

Note 1 to entry: Loudness level is expressed in phons (phon).

Note 2 to entry: For sound at the specified frequency, the loudness level in phons is equal to the mean-square sound pressure level (3.2.1.1) in decibels.

Note 3 to entry: See Reference [29].

[SOURCE:ISO 226:2003, 3.3, modified]

3.7.2.14

detectability index

d ′

square root of the detection index (3.6.1.14) [SOURCE: Reference [38] and ANSI/ASA S3.20-2015, 5.07]

3.7.3.1

soniferous

sound producing

3.7.3.2

bioacoustic communication signal

sound (3.1.1.1) produced intentionally by an organism, a signaller, for the purpose of transmitting information and evoking a response from a receiver

3.7.3.3

echolocation click

forward projected signal (3.1.5.8) of short duration whose primary function is echo ranging, target detection or discrimination

Note 1 to entry: Echolocation clicks are projected through the melon of toothed whales.

3.7.3.4

click train

rapid sequence of echolocation clicks (3.7.3.3) [SOURCE: Reference [41], modified]

3.7.3.5

drumming

sound production that involves contracting muscles of antennae, carapace, legs, skeletal system, or swim bladder

Note 1 to entry: “Drumming” can also refer to any mechanism responsible for producing the drumming sound.

3.7.3.6

stridulation

sound production that involves rubbing together of body parts, such as bony elements, carapace, spines, antennae, plucking tendons, or pharyngeal teeth

Note 1 to entry: Stridulation of antennae involves stick and slip friction.

3.7.3.7

grinding

stridulation (3.7.3.6) that involves frictional force between bony plates, appendages or teeth

3.7.3.8

snapping

sound production that involves the collapse of a cavitation bubble, created following rapid motion of an appendage such as a claw

Note 1 to entry: Snapping is associated with shrimp.