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Elastic Waves. Acoustics.

Problem 4.178

A source of sound with natural frequency v0=1.8kHzv_{0}=1.8 \mathrm{kHz} moves uniformly along a straight line separated from a stationary observer by a distance l=250 ml=250 \mathrm{~m}. The velocity of the source is equal to η=0.80\eta=0.80 fraction of the velocity of sound. Find: (a) the frequency of sound received by the observer at the moment when the source gets closest to him; (b) the distance between the source and the observer at the moment when the observer receives a frequency v=vnv=v_{n}

Reveal Answer
(a) v=v0/(1−η2)=5kHv=v_{0} /\left(1-\eta^{2}\right)=5 \mathrm{kH} (b) r=l1+η2=0.32 kmr=l \sqrt{1+\eta^{2}}=0.32 \mathrm{~km}
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