Book Description

The Wilson (October 1960) sound-speed equation is widely used for computing seawater sound speeds as a function of ttemperature, salinity, and pressure. The internal consistency of the Wilson laboratory measurements of sound speed, from which the Wilson equation is derived, is examined. The reported salinity of three of the seawater samples used in making the laboratory measurements seems to be in error by amounts larger than the generally accepted salinity measurement error. Moreover, an analysis, for the real- and open-ocean temperature-salinity-pressure domains, of the average difference between the laboratory sound-speed measurements and the sound speeds computed using Wilson's (October) equation showed systematic biases over temperature, salinity, and depth intervals of importance to acoustic applications. A new 13-variable sound-speed equation, using a realistic oceanic temperature-salinity-pressure domain consisting of 344 sound-speed measurements and a stepwise regression technique to evaluate the constants, is presented. This equation removes all significant sound-speed gradient bias from computations based on Wilson's (October) equation for temperature-salinity-pressure triplets observed in the open ocean. Since most presently available sound-speed data has been obtained using the Wilson equation, a procedure for obtaining an average correction as a function of temperature, salinity, and depth is presented. The procedure stresses important corrections of biased sound-speed gradients.