$A$ source of sound of frequency $256 \ Hz$ is moving rapidly towards a wall with a velocity of $5 \ m/s$. The speed of sound is $330 \ m/s$. If the observer is between the wall and the source,then the number of beats per second heard will be .... $Hz$.

$A$ sounding body of negligible dimension emitting a frequency of $150\, Hz$ is dropped from a height. During its fall under gravity,it passes near a balloon moving up with a constant velocity of $2\, m/s$ one second after it started to fall. The difference in the frequency observed by the man in the balloon just before and just after crossing the body will be: (Given: velocity of sound $= 300\, m/s$; $g = 10\, m/s^2$) (in $, Hz$)

$A$ whistle of frequency $540 Hz$ rotates in a horizontal circle of radius $2 m$ at an angular speed of $15 rad/s$. What is the highest frequency heard by a listener at rest with respect to the center of the circle (in $Hz$)? (Velocity of sound in air $= 330 m/s$)

With what velocity should an observer move relative to a stationary source so that they hear a sound of double the frequency of the source?

An observer starts moving with uniform acceleration $a$ towards a stationary sound source of frequency $f$. As the observer approaches the source,the apparent frequency $f'$ heard by the observer varies with time $t$ as:

$A$ person is observing two trains,one coming towards him and the other leaving with the same speed $4\, m/s$. If their whistling frequencies are $240\, Hz$ each,then the number of beats per second heard by the person will be: (if the velocity of sound is $320\, m/s$)