Calculation of Absorption Coefficient Using Average Temperature and Pressure.
NAVAL UNDERSEA WARFARE CENTER SAN DIEGO CALIF
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This note describes the investigation of an expression to be used in bottom bounce propagation models presently in use at NUWC Code D556. Recently an expression was developed to predict the acoustic absorption coefficient of seawater from the frequency, temperature, pressure and salinity. This expression was developed from a combination of existing equations in order to provide a single prediction expression valid under all operating conditions. In the past many methods for calculating the absorption coefficient have been used. These methods include the use of the surface temperature and 50 F in empirical expressions. This paper shows that it is necessary for the sake of accuracy to use the temperature averaged over the path of the propagating ray and to include the pressure term.