Abstract: The dependence of sound absorption in natural sea water on pH value at frequencies 2.91, 6.82 and 10.76 kHz has been measured using the resonator method. Measurements were made at 12.6℃ in the pH range 6.48 to 8.51. Comparison of the experimental results with predictions based on various equations is given. One of the principal objectives in this paper is to examine the contribution of the MgSO₄ absorption in sea water by reducing pH value to low enough values where the pH-dependent absorption losses become negligible. It seems clear that in order to predict sound absorption in sea water more accurately at both low and high frequency ranges with an united equation, the equation should include the MgHCO₃⁺ absorption term as well as the MgCO₃ term.