Question

How is the speed of sound in air affected by frequency of sound?

• A. no effect
• B. increases by increasing frequency
• C. decreases by increasing frequency
• D. insufficient data

Answer 1

Answer: (A)

no effect

A sound wave has a speed that is mathematically related to the frequency and the wavelength of the wave. The mathematical relationship between speed, frequency and wavelength is given by the following equation.
$Speed=Wavelength\times Frequency$
Even though wave speed is calculated using the frequency and the wavelength, the wave speed is not dependent upon these quantities. An alteration in wavelength does not affect (i.e., change) wave speed. Rather, an alteration in wavelength affects the frequency in an inverse manner. A doubling of the wavelength results in a halving of the frequency; yet the wave speed is not changed. The speed of a sound wave depends on the properties of the medium through which it moves and the only way to change the speed is to change the properties of the medium.