Editing Speed of sound (section)

===High-precision measurements in air===
The effect of impurities can be significant when making high-precision measurements. Chemical [[desiccant]]s 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<ref>Zuckerwar, Handbook of the speed of sound in real gases, p. 52</ref> 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 {{val|30|u=degC}} but corrected for temperature in order to report them at {{val|0|u=degC}}. The result was {{nobreak|331.45 ± 0.01 m/s}} for dry air at STP, for frequencies from {{val|93|u=Hz}} to {{nobreak|1,500 Hz}}.