$A$ and $B$ are two sources generating sound waves. $A$ listener is situated at $C$. The frequency of the source at $A$ is $500 \, Hz$. $A$ now moves towards $C$ with a speed of $4 \, m/s$. The number of beats heard at $C$ is $6$. When $A$ moves away from $C$ with a speed of $4 \, m/s$,the number of beats heard at $C$ is $18$. The speed of sound is $340 \, m/s$. The frequency of the source at $B$ is ..... $Hz$.

$A$ source and an observer approach each other with the same velocity $50 \, m/s$. If the apparent frequency is $435 \, s^{-1}$,then the real frequency is .... $s^{-1}$ (Take speed of sound $v = 332 \, m/s$)

$A$ student holds a tuning fork oscillating at $170 \,Hz$. He walks towards a wall at a constant speed of $2 \,ms^{-1}$. The beat frequency observed by the student between the tuning fork and its echo is (Velocity of sound $=340 \,ms^{-1}$ ) (in $\,Hz$)

$A$ source $(S)$ of sound has a frequency of $240 \ Hz$. When the observer $(O)$ and the source move towards each other at a speed $v$ with respect to the ground (as shown in Case $1$ in the figure),the observer measures the frequency of the sound to be $288 \ Hz$. However,when the observer and the source move away from each other at the same speed $v$ with respect to the ground (as shown in Case $2$ in the figure),the observer measures the frequency of the sound to be $n \ Hz$. The value of $n$ is:

$A$ table is revolving on its axis at $5$ revolutions per second. $A$ sound source of frequency $1000 \text{ Hz}$ is fixed on the table at $70 \text{ cm}$ from the axis. The minimum frequency heard by a listener standing at a distance from the table will be .... $\text{ Hz}$ (speed of sound $= 352 \text{ m/s}$)

$A$ train moving at a speed of $220\, m s^{-1}$ towards a stationary object,emits a sound of frequency $1000\, Hz$. Some of the sound reaching the object gets reflected back to the train as an echo. The frequency of the echo as detected by the driver of the train is ...... $Hz$. (Speed of sound in air is $330\, m s^{-1}$)