sound_absorption_sea_fisher.py

# Converted to Python from Matlab code in: 
# https://gorbatschow.github.io/SonarDocs/sound_absorption_sea_fisher.en/
# Sound absorption in sea
from numpy import * 

def sound_absorption_sea_fisher(T=None,D=None,f=None):

# Inputs
#   T: temperature \ degree Celsius
#   D: depth \ m
#   f: frequency \ kHz \ 10 < f < 400
# Outputs
#   alpha: absorption of sound in seawater \ dB/km

    T_kel = 273.1 + T
    P = D / 10.0
    f = f * 1e3

    # Boric
    A1 = (1.03e-8) + (2.36e-10)*T - (5.22e-12)*(T**2)
    P1 = 1
    f1 = (1.32e3)*T_kel*exp(-1700/T_kel)
    Boric = (A1*P1*f1*(f**2))/((f**2)+(f1**2))
    Boric = Boric * 8686

    # MgSO4
    A2 = (5.62e-8) + (7.52e-10)*T
    P2 = 1 - (10.3e-4)*P + (3.7e-7)*(P**2)
    f2 = (1.55e7)*T_kel*exp(-3052/T_kel)
    MgSO4 = (A2*P2*f2*(f**2))/((f**2)+(f2**2))
    MgSO4 = MgSO4 * 8686

    # H2O
    A3 = (55.9 - 2.37*T + (4.77e-2)*(T**2) - (3.48e-4)*(T**3))*(1e-15)
    P3 = 1 - (3.84e-4)*P + (7.57e-8)*(P**2)
    H2O = A3*P3*(f**2)
    H2O = H2O * 8686

    # Total
    alpha = (Boric + MgSO4 + H2O)

return alpha, Boric, MgSO4, H2O