Problem 4.180

A source of sonic oscillations with frequency $v_{0}=1700 \mathrm{~Hz}$ and a receiver are located on the same normal to a wall. Both the source and the receiver are stationary, and the wall recedes from the source with velocity $u=6.0 \mathrm{~cm} / \mathrm{s} .$ Find the beat frequency registered by the receiver. The velocity of sound is equal to'. $v=340 \mathrm{~m} / \mathrm{s}$.