Question

A bat flies at a steady speed of 4 m/s emitting a sound of f = 90000 Hz. It is flying horizontally towards a vertical wall. What is the frequency of the reflected sound as detected by the bat?
(Take velocity of sound in air as 330 m/s).

Answer 1

Answer on Question#38567 – Physics – Acoustics

A bat flies at a steady speed of 4 m/s emitting a sound of f = 90000 Hz. It is flying horizontally towards a vertical wall. What is the frequency of the reflected sound as detected by the bat?

(Take velocity of sound in air as 330 m/s).

Solution:

Doppler Effect equation:

$$n' = \left(\frac{v + v_0}{v - v_0}\right)n = 90\,\mathrm{kHz} \cdot \left(\frac{340\,\frac{\mathrm{m}}{\mathrm{s}} + \frac{4\,\mathrm{m}}{\mathrm{s}}}{340\,\frac{\mathrm{m}}{\mathrm{s}} - 4\,\frac{\mathrm{m}}{\mathrm{s}}}\right) = 92\,\mathrm{kHz}$$

Answer: the frequency of the reflected sound is 92 kHz.