Question

A musician on a moving vehicle plays a tone at $880\, Hz$ note. When the vehicle was approaching a listener, he receives it as $888\, Hz$ tone. The speed of the vehicle is (Assume the velocity of sound is $333\, m / s$.)

• A. 6 m / s
• B. 5 m / s
• C. 3 m / s
• D. 1 m / s

Answer 1

Answer: (C)

Given, $n_{0}=880\, Hz$ (Frequency of sound produced by musician), $n=888\, Hz$ (frequency of sound observed by observer and speed of sound, $v=333\, m / s$ ).
We know that, when sound source is in motion and observer is stationary, frequency heard,
$n =\frac{n_{0} v}{v-v_{s}}$
$\Rightarrow v_{s}=v\left[1-\frac{n_{0}}{n}\right]$
$\Rightarrow v_{s} =333\left[1-\frac{880}{888}\right]=3\, m / s$