The speed of sound in standard seawater (diluted with pure water and evaporated) has been measured relative to pure water with a Nusonics velocimeter as a function of temperature (0 to 40°C, at 5° intervals) and salinity (5 to 40&, at 5%0 intervals) at 1 atm. The results have been fitted to an equation of the form c = c° + A S(%o) + B S(%0)312 + CS(%o)2, where c° is the speed of sound in pure water, SS(%0) is the salinity in parts per thousand, and A, B, and C are temperature-dependent parameters. The sound speeds fit this equation to a standard deviation of 0.04 m sec-1 over the entire temperature and salinity range. Over the oceanographic range our results, on the average, agree with the work of Wilson to ±0.5 m sec-1(max 1.08 m sec-1) and with the work of Del Grosso and Mader to ±0.05 m sec-1(max 0.14 m sec-1). In the low-salinity range, 5-25%o salinity) our results, on the average, agree with the work of Wilson to ±0.3 m sec-1(max 1.1m sec-1) and with the work of Del Grosso and Mader to within ±0.1 m sec-1(max 0.20 m sec-1). From these comparisons it is clear that the 1-atm sound speeds of Del Grosso and Mader are more reliable than those determined by Wilson over the oceanographic range as well as at lower salinities (which is outside of the range of Del Grosso and Mader's measurements). The adiabatic and isothermal compressibilities of seawater solutions reliable to ±0.003 X 10–6 bar-1 have been determined from the sound speeds. The isothermal compressibilities are in excellent agreement (avg. dev. ±0.02 X 10–6 bar) with the direct measurements of Lepple and Millero. The specific heat of seawater solutions at constant volume has also been determined from the sound-derived isothermal compressibilities.
ASJC Scopus subject areas
- Arts and Humanities (miscellaneous)
- Acoustics and Ultrasonics