$A$ source of sound of frequency $500 Hz$ is moving towards an observer with velocity $30 m/s$. The speed of sound is $330 m/s$. The frequency heard by the observer will be .... $Hz$

$A$ sound source is moving in a circle and an observer is outside the circle at $O$ as shown in the figure. If the frequencies as heard by the listener are $\nu_1, \nu_2$ and $\nu_3$ when the source is at positions $A, B$ and $C$ respectively,then:

$A$ source of sound is travelling at $\frac{100}{3} \, m/s$ along a road,towards a point $A$. When the source is $3 \, m$ away from $A$,a person is standing at a point $O$ on a road perpendicular to the path of the source. The distance of $O$ from $A$ at that time is $4 \, m$. If the original frequency is $640 \, Hz$,then the apparent frequency heard by the person is ...... $Hz$ (speed of sound is $340 \, m/s$).

$A$ whistle $S$ of frequency $f$ revolves in a circle of radius $R$ at a constant speed $v$. What is the ratio of maximum and minimum frequency detected by a detector $D$ at rest at a distance $2R$ from the center of the circle as shown in the figure?

$A$ person feels a $2.5\%$ difference in the frequency of a motor-car horn. If the motor-car is moving towards the person and the velocity of sound is $320\, m/s$,then the velocity of the car will be:

$A$ source producing sound of frequency $170 \, Hz$ is approaching a stationary observer with a velocity $17 \, ms^{-1}$. The apparent change in the wavelength of sound heard by the observer is (speed of sound in air $= 340 \, ms^{-1}$) ..... $m$