Problem 4.174

A source of sonic oscillations with frequency $v_{0}=1000 \mathrm{~Hz}$ moves at right angles to the wall with a velocity $u=0.17 \mathrm{~m} / \mathrm{s} .$ Two stationary receivers $R_{1}$ and $R_{2}$ are located on a straight line, coinciding with the trajectory of the source, in the following succession: $R_{1}$ -source- $R_{2}$ -wall. Which receiver registers the beatings and what is the beat frequency? The velocity of sound is equal to $v=$ $=340 \mathrm{~m} / \mathrm{s}$