Underwater acoustics
API reference
Compute sound speed in water in m/s, given:
- water
temperature
in °C salinity
in pptdepth
in meters- void fraction (
γ
) in bubbly water - sound speed in gas (
cₐ
) ifγ
> 0 - ratio of density of water to gas (
ρᵣ
) ifγ
> 0
Implementation based on Mackenzie (1981), Wood (1964) and Buckingham (1997).
Compute volume acoustic absorption coefficient in water, given:
frequency
in Hzdistance
in meterssalinity
in ppt- water
temperature
in °C depth
in meterspH
of water
The result is a unitless linear scale factor for sound pressure over the given distance
. To get absorption in terms of dB / m, set distance = 1.0
and convert the result to decibels. For instance, at a frequency of 100 kHz:
julia> A = absorption(100e3, 1.0)
0.9959084838594522
julia> α = -20log10(A)
0.035611359656810865
Implementation based on the Francois and Garrison (1982) model.
Compute complex reflection coefficient at a fluid-fluid boundary, given:
- angle of incidence
θ
(angle to the surface normal) - relative density of the reflecting medium to incidence medium
ρᵣ
- relative sound speed of the reflecting medium to incidence medium
cᵣ
- dimensionless absorption coefficient
δ
Implementation based on Brekhovskikh & Lysanov. Dimensionless absorption coefficient based on APL-UW Technical Report 9407.
Compute resonance frequency of a freely oscillating has bubble in water, given:
- bubble
radius
in meters depth
of bubble in water in meters- gas ratio of specific heats ‘γ’
- atmospheric pressure ‘p₀’ in Pa
- density of water ‘ρ’ in kg/m³
- acceleration due to gravity ‘g’ in m/s²
This ignores surface-tension, thermal, viscous and acoustic damping effects, and the pressure-volume relationship is taken to be adiabatic. Implementation based on Medwin & Clay (1998).