Proper water properties calculator: Speed of sound in water

God speed on your way! (C) An archaic expression

0. Brief description. Very basic theory.

In real-world applications, speed of sound in water is a function of water temperature t, water salinity s and hydrostatic pressure P. The range of these three parameters in most of Earth's water bodies varies from -2 to 40°C for temperature, 0..42 PSU for salinity, and from ~1 to 1100 bar for pressure. So, the speed of sound varies from approximately 1400 m/s in cold freshwater under low pressure to up to 1700 m/s in warm saline water under high pressure. There is a lot slightly different empiric equations for estimation of the speed of sound in water, obtained from big datasets of measurements. One can find it in works, listed here. Here we use the equation from the work of Chen and Millero[1] pp 1129-1135, so-called UNESCO Equation. It uses pressure rather than depth as a parameter. It is more convenient since the depth itself cannot be measured directly in most cases.

1. Calculation

Parameter	Notation	Range	Units
Water temperature	t	-2 .. 40	°C
Hydrostatic pressure	P	10³ .. 10⁶	mBar
Water salinity	s	0 .. 42	PSU
Speef of sound	v		m/s

C-T. Chen and F.J. Millero, Speed of sound in seawater at high pressures (1977) J. Acoust. Soc. Am. 62(5).

This calculator is made with UCNLPhysics free and open source library.

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