![]() In particular, Del Grosso’s algorithm is thought to be more accurate for calculating sound-speeds at deeper depths, where sound is moving slower (Spiesberger and Metzger, 1991 Spiesberger, 1993). Although the Chen and Millero/UNESCO equation is the internationally accepted standard ( Fofonoff and Millard, 1983) for calculating sound-speed in seawater, scientists have questioned whether it is the best option for all applications (e.g. Below this depth, however, experiments have found that they tend to diverge (e.g. ![]() In the upper water column (top 1000dbars), these equations tend to give similar results. There are many studies looking at which equation is best to use, for example Dushaw et al. The Wilson equation for speed of sound in water The Del Grosso equation for speed of sound in water Please see below for the numerical values of the ITS-90 coefficients from Wong and Zhu (1995). The UNESCO equation for speed of sound in water Please note that the Wilson sound-speed equation below uses the IPTS-68 temperature scale. In addition, see Wong and Zhu (1995) for the full list of coefficients for the UNESCO and Del Grosso equations using the ITS-90 temperature scale. (1993) for a summary of these equations and associated laboratory experiments. There are three common equations used to calculate sound-speed in seawater: Wilson (1960 the first accurate measurements of sound-speed in distilled water and seawater), Del Grosso (1974), and Chen and Millero (1977, currently the UNESCO standard). What equations are available to calculate sound-speed in water? From these experiments, scientists fit the data with complex polynomials such that temperature, salinity, and pressure simply need to be plugged into these equations to calculate sound-speed for any given parcel of water (see Wilson, 1960 Del Grosso, 1974 Chen and Millero, 1977). The original equations developed were based on precise lab experiments that measured the time for a sound pulse to travel a known distance at various combinations of temperature, salinity, and pressure ( Wilson, 1959). Over the last 50 years, numerous equations have been developed to describe sound velocity in seawater. How do we calculate the speed of sound in water? Therefore, when studying ocean acoustics and ocean soundscapes, the speed of sound is often an important variable to consider for many oceanographers. Sound propagation in particular depends on variations in sound-speed ( Leroy and Parthiot, 1998). It increases by approximately 1.3m/s per 1PSU increase in salinity, 4.5m/s per 1☌ increase in temperature, and 1.7m/s per 1dbar increase in pressure. In the oceans, the speed of sound varies between 1450m/s and 1570m/s. The speed of sound in water depends on temperature, salinity, and pressure, and is therefore not uniform throughout different water environments. Sound-speed in water is a quantification of how fast sounds travel in water. What is speed of sound in water and why do we measure it? ![]()
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