Comments on ‘‘On equations for the speed of sound in seawater’’ [J. Acoust. Soc. Am. 93, 255–275 (1993)] Available to Purchase

The recent measurements of acoustic arrival patterns [Dushaw et al., J. Acoust. Soc. Am. 93, 255–275 (1993); Spiesberger and Metzger, J. Acoust. Soc. Am. 89, 1697–1700 (1991); 89, 2677–2688 (1991)] indicate that the sound‐speed equation of Del Grosso [J. Acoust. Soc. Am. 56, 1084–1091 (1974)] may be more reliable than the equation of Chen and Millero [J. Acoust. Soc. Am. 62, 1129–1135 (1977)] at low temperatures (0° to 15 °C) and high pressures (300 to 1000 bar). In this paper the possible causes of the difference and the resultant effect on the equation of state of seawater are discussed. The error in the sound‐speed equation of Chen and Millero originated from the unreliable sound speeds for pure water determined by Wilson [J. Acoust. Soc. Am. 31, 1067–1072 (1959)] at low temperatures and high pressures. This difference does not affect the equation of state of seawater within the standard error of the equation (5×10⁻⁶ cm³/g in the specific volume at high pressures, v^P). A correction has been derived that is valid from 0° to 15 °C to 1000 bar that can be used to correct the sound‐speed equation of Chen and Millero. This correction allows one to use their equation over a much wider range of temperature, pressure, and salinity than the Del Grosso equation.