Compute the sound absorption of seawater, in dB/m
The frequency of sound, in Hz.
either practical salinity (in which case
in-situ temperature [degC], defined
on the ITS-90 scale. This scale is used by GSW-style calculation (as
requested by setting
character string indicating the formulation to use, either
Salinity and pH are ignored in this formulation. Several formulae may be found in the literature, and they give results differing by 10 percent, as shown at  for example. For this reason, it is likely that more formulations will be added to this function, and entirely possible that the default may change.
Sound absorption in dB/m.
1. F. H. Fisher and V. P. Simmons, 1977. Sound absorption in sea water. J. Acoust. Soc. Am., 62(3), 558-564.
2. R. E. Francois and G. R. Garrison, 1982. Sound absorption based on ocean measurements. Part II: Boric acid contribution and equation for total absorption. J. Acoust. Soc. Am., 72(6):1879-1890.
Other functions that calculate seawater properties:
1 2 3 4 5 6 7 8 9 10
## Fisher & Simmons (1977 table IV) gives 0.52 dB/km for 35 PSU, 5 degC, 500 atm ## (4990 dbar of water)a and 10 kHz alpha <- swSoundAbsorption(35, 4, 4990, 10e3) ## reproduce part of Fig 8 of Francois and Garrison (1982 Fig 8) f <- 1e3 * 10^(seq(-1,3,0.1)) # in KHz plot(f/1000, 1e3*swSoundAbsorption(f, 35, 10, 0, formulation='fr'), xlab=" Freq [kHz]", ylab=" dB/km", type='l', log='xy') lines(f/1000, 1e3*swSoundAbsorption(f, 0, 10, 0, formulation='fr'), lty='dashed') legend("topleft", lty=c("solid", "dashed"), legend=c("S=35", "S=0"))
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