ISO 17201-4:2006 音響—射撃範囲からのノイズ—パート4：発射体の音の予測 | ページ 6

3.1

streamlined projectile

body of revolution of which the first derivative of the cross-sectional area A ( x ) at a distance x behind the nose of the body is continuous for 0 ≤ x < l_p

Note 1 to entry: For the definition of effective projectile length, l_p, see 3.2.

3.2

effective projectile length

l _p

distance between the nose and the cross-section with the maximum diameter of the projectile

3.3

N-wave

3.4

duration time

T_c

time between two pressure increases of the N-wave

Note 1 to entry: The duration time is expressed in seconds (s).

Note 2 to entry: Resulting from the non-linear acoustic effects, T_c, for the N-wave along the sound path will change.

3.5

characteristic frequency

f_c

Note 1 to entry: The characteristic frequency is expressed in Hertz (Hz).

3.6

coordinate system ( x, y )

plane co-ordinate system describing geometry, where the x -axis denotes the line of fire with x = 0 at the muzzle, and the y -axis measures the perpendicular distance from the line of fire in any plane around the line of fire

Note 1 to entry: The sound field of projectile sound is rotational symmetric around the line of fire.

Note 2 to entry: The co-ordinates are given in metres (m).

3.7

coherence distance

R_coh

distance between the source point on the trajectory and a receiver beyond which the contribution of different parts of the trajectory are incoherent due to atmospheric turbulence

Note 1 to entry: The coherence distance is expressed in metres (m).

3.8

Mach number

M

ratio of projectile speed to local sound speed

3.9

source sound exposure level

L_{E ,s}

sound exposure level expected at a distance of 1 m from the source point

Note 1 to entry: The source sound exposure level is expressed in decibels (dB).

Note 2 to entry: The reference distance of 1 m is “measured” in the direction of the receiver and not perpendicular to the trajectory.

3.10

source point

point where a line from the receiver perpendicular to the wave front intersects the projectile trajectory

Note 1 to entry: In this part of ISO 17201, the source point is used to represent the trajectory that in principle is a line source [see Equation (4)].

3.11

projectile launch speed

v_p0

speed of the projectile at the muzzle

Note 1 to entry: The muzzle velocity is expressed in metres per second (m/s).

3.12

projectile speed

v_p

speed of the projectile along the trajectory

Note 1 to entry: The projectile speed is expressed in metres per second (m/s).

Note 2 to entry: Published data on the projectile speed as a function of distance refer to air density at sea level. For other elevations above sea level, changes of density could have to be taken into account.

3.13

end speed

v_pe

speed of the projectile as it hits the target or at the trajectory point where the Mach number is reduced to 1,01

Note 1 to entry: The end speed is expressed in metres per second (m/s).

3.14

reference sound speed

adiabatic sound speed averaged over a period of at least 10 min

Note 1 to entry: The reference sound speed is expressed in metres per second (m/s).

3.15

fluctuating effective sound speed

sum of the instantaneous adiabatic sound speed and the instantaneous horizontal wind velocity component in the direction of the sound propagation

Note 1 to entry: The fluctuating effective sound speed is expressed in metres per second (m/s).

3.16

standard deviation of the fluctuating acoustical index of refraction

μ₀

standard deviation of the ratio of the reference sound speed to the fluctuating effective sound speed

Note 1 to entry: In accordance with [5], a value of μ₀² = 10^–5 is used within the context of this part of ISO 17201 [see Equation (12)].

3.17

projectile speed change

k

local change of projectile speed along the trajectory per length unit of trajectory

Note 1 to entry: The speed change is expressed in reciprocal seconds [(m/s · m) = 1/s].

Note 2 to entry: It is negative for non-self-propelled projectiles.