What is the speed of sound in air, water .. ?

The speed of sound in air at a temperature of 0 degC and 50% relative
humidity is 331.6 m/s. The speed is proportional to the square root of
absolute temperature and it is therefore about 12 m/s greater at 20
degC. The speed is nearly independent of frequency and atmospheric
pressure but the resultant sound velocity may be substantially altered
by wind velocity.

A good approximation for the speed of sound in other gases at standard
temperature and pressure can be obtained from

c = sqrt (gamma x P / rho)

where gamma is the ratio of specific heats, P is 1.013E5 Pa and rho is
the density.

The speed of sound in water is approximately 1500 m/s. It is possible
to measure changes in ocean temperature by observing the resultant
change in speed of sound over long distances. The speed of sound in an
ocean is approximately:

c = 1449.2 + 4.6T – 0.055T^2 + 0.00029T^3 + (1.34-0.01T)(S-35) + 0.016z

T temp in degrees Celsius, S salinity in parts per thousand
z is depth in meters

See also CRC Handbook of Chemistry & Physics for some other substances
and Dushaw & Worcester JASA (1993) 93, pp255-275 for sea water.