<P> Kundt's tube is an example of an experiment which can be used to measure the speed of sound in a small volume . It has the advantage of being able to measure the speed of sound in any gas . This method uses a powder to make the nodes and antinodes visible to the human eye . This is an example of a compact experimental setup . </P> <P> A tuning fork can be held near the mouth of a long pipe which is dipping into a barrel of water . In this system it is the case that the pipe can be brought to resonance if the length of the air column in the pipe is equal to (1 + 2n) λ / 4 where n is an integer . As the antinodal point for the pipe at the open end is slightly outside the mouth of the pipe it is best to find two or more points of resonance and then measure half a wavelength between these . </P> <P> Here it is the case that v = fλ . </P> <P> The effect from impurities can be significant when making high - precision measurements . Chemical desiccants can be used to dry the air, but will in turn contaminate the sample . The air can be dried cryogenically, but this has the effect of removing the carbon dioxide as well; therefore many high - precision measurements are performed with air free of carbon dioxide rather than with natural air . A 2002 review found that a 1963 measurement by Smith and Harlow using a cylindrical resonator gave "the most probable value of the standard speed of sound to date ." The experiment was done with air from which the carbon dioxide had been removed, but the result was then corrected for this effect so as to be applicable to real air . The experiments were done at 30 ° C but corrected for temperature in order to report them at 0 ° C. The result was 331.45 ± 0.01 m / s for dry air at STP, for frequencies from 93 Hz to 1,500 Hz . </P>

What is the measure of how high or low a sound is