swSoundAbsorption {oce} | R Documentation |
Compute the sound absorption of seawater, in dB/m
swSoundAbsorption(frequency, salinity, temperature, pressure, pH = 8, formulation = c("fisher-simmons", "francois-garrison"))
frequency |
The frequency of sound, in Hz. |
salinity |
either practical salinity (in which case |
temperature |
in-situ temperature [degC], defined
on the ITS-90 scale. This scale is used by GSW-style calculation (as
requested by setting |
pressure |
pressure [dbar] |
pH |
seawater pH |
formulation |
character string indicating the formulation to use, either
of |
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 [3] 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.
Dan Kelley
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.
3. http://resource.npl.co.uk/acoustics/techguides/seaabsorption/
Other functions that calculate seawater properties: T68fromT90
,
T90fromT48
, T90fromT68
,
swAbsoluteSalinity
,
swAlphaOverBeta
, swAlpha
,
swBeta
, swCSTp
,
swConservativeTemperature
,
swDepth
, swDynamicHeight
,
swLapseRate
, swN2
,
swPressure
, swRho
,
swRrho
, swSCTp
,
swSTrho
, swSigma0
,
swSigma1
, swSigma2
,
swSigma3
, swSigma4
,
swSigmaTheta
, swSigmaT
,
swSigma
, swSoundSpeed
,
swSpecificHeat
, swSpice
,
swTFreeze
, swTSrho
,
swThermalConductivity
,
swTheta
, swViscosity
,
swZ
## 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"))