Question

A whistle produces sound of frequency of 1.00 kHz. If a listener moves with a speed of 30 m/s away from the whistle, what frequency does this person hear if the sound speed is 340 m/s

Answer 1

Answer:

The frequency the listener hears is 911.765 Hz.

Explanation:

The speed of a sound is 340 m/s

The speed of listener is 30 m/s in a direction away from the whistle.

The speed of the listener with respect to the sound waves from the whistle

= ( 340 - 30) m/s

= 310 m/s

This because the direction of the sound waves from the whistle and the direction of travel of the listener are the same, that is, both are traveling away from the whistle.

Therefore from the formula we get

⇒     $\frac{f_2}{f_1} = \frac{v_2}{v_1}$            ⇒  $f_2$ = $1000 \times \frac{310}{340} = 911.765 \hspace{0.1cm} Hz$

The frequency the listener hears is 911.765 Hz.