Question

A sparrow chases a crow with a speed of 4.0 m/s, while chirping at a frequency of 850.0 Hz. What frequency of sound does the crow hear as he flies away from the sparrow with a speed of 3.0 m/s?

Answer 1

`832,653Hz`

Explanation:

By the Doppler effect of sound waves, the new frequency`f'` observed is given by

`f'=f((v+-v_o)/(v+-v_s))`,

where `f'>f` for relative motion of source and observer towards each other and `f'<f` for relative motion of source and observer away from each other.

So in this particular case, and taking the speed of sound in air to be `v=340m//s`, and assuming the speed of the crow is 4m/s and that of the sparrow 3m/s (as question is a bit unclear), we get

`f'=850((340-4)/(340+3))=832,653Hz`