Question

The velocity of sound in air is not affected by change in

• A. the moisture content of the air.
• B. the temperature of air.
• C. the atmospheric pressure.
• D. the composition of air.

Answer 1

Answer: (C)

the atmospheric pressure.

The speed of sound depends on temperature. The formula relating speed of sound and temperature is as follows:

$v=331+0.6\times T$, where $T$ is temperature in absolute scale and $v$ is in $m/s$.
Humidity has little effect on the speed of sound.
Air pressure has no effect at all in an ideal gas approximation. This is because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out each other, leaving only the effect of temperature.
Composition of air has also almost no effect on the speed of sound.