Waves

An audio transmitter (T) and a receiver (R) are hung vertically from two identical massless strings of length 8m with their pivots well separated along the X axis. They are pulled from the equilibrium position in opposite directions along the X axis by a small angular amplitude θ0=cos−1(0.9) and released simultaneously. If the natural frequency of the transmitter is 660 Hz and the speed of sound in air is 330m∕s, the maximum variation in the frequency (in Hz) as measured by the receiver (Take the acceleration due to gravity g=10m∕s2 ) is ____