Question

Explain the effects of pressure, temperature and humidity on velocity of sound in air.

Answer 1

Velocity of sound in air depends on the factors Pressure P, humidity and temperature of air too.

       v ∞  √T
       v ∞ √(P/d)
 
Velocity of sound is proportional directly to square root of temperature. Also velocity is proportional to the pressure divided by the density.

If only pressure increases, keeping other factors constant, then velocity increases.

If only density increases keeping pressure constant then velocity decreases.
So when humidity increases in air, its density decreases. This is because water drops have less molecular mass compared to N2 and O2. 

     => So velocity of sound increases with humidity.

When temperature increases the speed of sound increases.

Answer 2

Explanation:

Velocity of sound in air depends on the factors Pressure P, humidity and temperature of air too.

V∞ √T

v∞ √(P/d)

Velocity of sound is proportional directly to square root of temperature. Also velocity is proportional to the pressure divided by the density.

If only pressure increases, keeping other factors constant, then velocity increases.

If only density increases keeping pressure constant then velocity decreases.

So when humidity increases in air, its density decreases. This is because water drops have less molecular mass compared to N2 and 02.

=> So velocity of sound increases with humidity.

When temperature increases the speed of sound increases.