ISO 13474:2009 音響学 — 環境騒音評価の目的で衝撃音イベントの音曝露レベルの分布を計算するためのフレームワーク | ページ 6

3.1

atmospheric absorption

attenuation of sound by air, resulting from viscous molecular processes, molecular rotation and molecular vibration

3.2

atmospheric-absorption class

range of meteorological parameters yielding approximately the same attenuation of sound by air, all within a specified uncertainty

Note 1 to entry: See also atmospheric absorption.

3.3

atmospheric stability

tendency of the atmosphere to reduce or enhance vertical motion of the air

Note 1 to entry: Enhanced (or reduced) vertical motion of the air usually implies enhanced (or reduced) atmospheric turbulence.

3.4

atmospheric-stability class

subset formed from partitioning the set of atmospheres according to stability

Note 1 to entry: See also atmospheric stability.

3.5

direct path

position displacement vector, in metres, originating at the source and describing a straight trajectory terminating at the receiver

Note 1 to entry: The direct path may intercept objects such as buildings or terrain.

3.6

directed sound speed

algebraic sum of the adiabatic sound speed and the horizontal component of the wind velocity along the direct path

Note 1 to entry: Directed sound speed is expressed in metres per second.

3.7

directed sound speed profile

sound speed along the direct path, expressed as a function of height

Note 1 to entry: See directed sound speed.

3.8

event

single short burst, or rapid sequence of bursts, associated with a sound source

Note 1 to entry: A single activity, such as firing a gun, could produce multiple sound events. In the case of firing an explosive projectile from a high-velocity gun, sound events are associated with each of the following sound sources: the muzzle blast, the ballistic shock and the projectile impact.

3.9

event duration

T

time interval starting just before immission, at time t₁, and ending just after immission, at time t₂, to encompass all significant sound of a single short blast or rapid sequence of blasts

Note 1 to entry: The time interval t₂ − t₁ is expressed in seconds.

3.10

exceedance level

sound level of a stated type, in decibels, exceeded by no more and no less than a stated percentage of samples

Note 1 to entry: The sampling set shall be identified, e.g. percentage of times during a stated time interval or percentage of firing events from an exercise.

3.11

excess attenuation

that part of sound attenuation not included when accounting for geometric divergence (from a small sound source in non-refracting and non-moving air), atmospheric absorption of sound waves along the direct path from source to receiver and attenuation of screens and/or barriers

Note 1 to entry: Excess attenuation is expressed in decibels.

3.12

excess-attenuation class

range of combined directed sound speed profiles and ground types yielding approximately the same attenuations, all within a specified uncertainty

3.13

ground condition

sound reflection and absorption properties of outdoor surface(s) along the sound path(s) between source and receiver

3.14

impulsive sound event

occurrence of a single short blast or series of blasts of sound in which the pressure-time history, close to the source, includes a rapid rise to the peak sound pressure followed by decay of the pressure

3.15

sound pressure

p

difference between instantaneous total pressure and static pressure

[SOURCE: ISO 80000-8:2007, 8-9.2]

Note 1 to entry: Sound pressure is expressed in pascals.

Note 2 to entry: The symbol p is often used without modification to represent a root-mean-square sound pressure. However, root-mean-square values should preferably be indicated by the subscript"eff".

[SOURCE: ISO/TR 25417:2007, 2.1]

3.16

open-air explosion

blast, taking place out-of-doors, in which no part of the exploding material or gaseous products is limited by a container or any other obstructing surface

3.17

peak sound pressure

p_peak

greatest absolute sound pressure during a certain time interval

Note 1 to entry: Peak sound pressure is expressed in pascals.

Note 2 to entry: A peak sound pressure may arise from a positive or negative sound pressure.

[SOURCE: ISO/TR 25417:2007, 2.4]

Note 3 to entry: This definition is technically in accordance with ISO 10843.

3.18

peak sound pressure level

L_{p , peak}

Note 1 to entry: Because of practical limitations of the measuring instruments, is always understood to denote the square of a frequency-weighted or frequency-band-limited peak sound pressure. If a specific frequency weighting as specified in IEC 61672-1 is applied, this should be indicated by appropriate subscripts; e.g. L_{p , C peak} denotes the C-weighted peak sound pressure level.

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

3.19

receiver height

h_r

distance, in metres, of the sound receiver above the local ground surface

Note 1 to entry: This definition is technically in accordance with ISO 9613-2.

3.20

replica atmosphere

conditions representing the atmosphere corresponding to a stated excess-attenuation class and a stated atmospheric-absorption class

3.21

roughness height

distance above local ground level to the elevation where the time-average horizontal wind velocity becomes non-zero

Note 1 to entry: The roughness height is expressed in metres.

Note 2 to entry: The time interval over which the wind velocity is averaged is 300 s.

3.22

sound exposure

E_T

Note 1 to entry: Sound exposure is expressed in pascals squared seconds, Pa²·s.

Note 2 to entry: Because of practical limitations of the measuring instruments, p² is always understood to denote the square of a frequency-weighted and frequency-band-limited sound pressure. If a specific frequency weighting as specified in IEC 61672-1 is applied, this should be indicated by appropriate subscripts; e.g. E_{A,1 h} denotes the A-weighted sound exposure over 1 h.

Note 3 to entry: When applied to a single event of impulsive or intermittent sound, the quantity is called"single-event sound exposure" and the symbol E is used without a subscript.

Note 4 to entry: This definition is technically in accordance with ISO 80000-8:2007, 8-18.

[SOURCE: ISO/TR 25417:2007, 2.6]

3.23

sound exposure level

L_{E , T}

Note 1 to entry: If a specific frequency weighting as specified in IEC 61672-1 is applied, this should be indicated by appropriate subscripts; e.g. L_{E ,A,1 h} denotes the A-weighted sound exposure level over 1 h.

Note 2 to entry: When applied to a single event, the quantity is called"single-event sound exposure level" and the symbol L_E is used without further subscript.

Note 3 to entry: This definition is technically in accordance with ISO 80000-8:2007, 8-24.

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

3.24

source height

h_s

distance of the sound source above the local ground surface

Note 1 to entry: The source height is expressed in metres.

Note 2 to entry: This definition is technically in accordance with ISO 9613-2.

3.25

source forward direction

horizontal and vertical rotation angles assigned as references in the source-directivity coordinate system

3.26

adiabatic sound speed

c

speed of sound in the absence of ambient flow

Note 1 to entry: The speed is expressed in metres per second.