Two factories are sounding their sirens at $800 \, Hz$. $A$ man walks from one factory to the other at a speed of $2 \, m/s$. The velocity of sound is $320 \, m/s$. The number of beats heard by the person in one second will be:

$A$ whistle of frequency $500 \, Hz$ tied to the end of a string of length $1.2 \, m$ revolves at $400 \, rev/min$. $A$ listener standing some distance away in the plane of rotation of the whistle hears frequencies in the range (speed of sound $= 340 \, m/s$):

$A$ source of sound is moving with a constant velocity of $30 \,m/s$ emitting a note of frequency $256 \,Hz$. The ratio of frequencies observed by a stationary observer while the source is approaching him and after it crosses him is [speed of sound in air $= 330 \,m/s$].

Two sirens situated one kilometer apart are producing sound of frequency $330 \ Hz$. An observer starts moving from one siren to the other with a speed of $2 \ m/s$. If the speed of sound is $330 \ m/s$,what will be the beat frequency heard by the observer?

$A$ sound source is moving towards a stationary observer with $\frac{1}{10}$th the speed of sound. The ratio of apparent to real frequency is

$A$ motorcycle starts from rest and accelerates along a straight path at $2 \; m/s^2$. At the starting point of the motorcycle,there is a stationary electric siren. How far has the motorcycle gone when the driver hears the frequency of the siren at $94 \%$ of its original value (in $; m$)? (Speed of sound $= 330 \; m/s$)