Hydrophones

If it is without justification, it came from the rulebook.

Data:
Frequency of signal: 0.5 Hz
Frequency of sound: 22-30 kHz (page 6 in rulebook
Duration: 1.3 ms
Pulse train: |____|_____|____|_____|
t(s) 0 .9 2.0 2.9 4.0
Intensity level: ~ 187 dB (assumed at 0.5 m)
Reference pressure: 1 uPa (as opposed to airborne acoustics with 20 uPa
Scale estimates:
depth: 20m
distance: 50 m
Sound in water at 80C: 4919 ft/s
1499 m/s (http://www.engineeringtoolbox.com/sound-speed-water-d_598.html)
Formulae:
(source: http://www.sengpielaudio.com/calculator-distance.htm)
Sound intensity: power per unit area
Sound pressure: force per unit area
I ~ p^2
sound level: 10 log_10(I / I_0) = 20 log_10(p / p_0)

Possibly useful basic Functions:
def levelDrop(initial, x):
‘’’ Computes the drop in intensity level as it diffuses over distance x.‘’’
return initial – 10 * math.log(x / r_0)

def presFromLevel(lvl):
‘’’ Changes intensity to sound pressure in Pa.‘’’
return p_0 * 10 ** (lvl / 20.0)

def levelFromPres(pres):
’’’Changes sound pressure to intensity (logarithmic, hence unitless).‘’’
return 20 * math.log(pres / p_0) / math.log(10) # Change of base from ln

def sensConvert(sensitivity):
‘’’ Converts a sensitivity from dB re. 1 V/uPa to V / MPa.‘’’
return 10 ** ((sensitivity / 20) + 12)

1. Source: ondacorp.com/tecref_tutorialhydrophone_converting.shtml