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?

Oct 29, 2015

Answer:

$832 , 653 H z$

Explanation:

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

$f ' = f \left(\frac{v \pm {v}_{o}}{v \pm {v}_{s}}\right)$,

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 $v = 340 m / s$, 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

$f ' = 850 \left(\frac{340 - 4}{340 + 3}\right) = 832 , 653 H z$