$A$ train blowing a whistle of frequency $320\,Hz$ approaches an observer standing on the platform at a speed of $66\,m/s$. The frequency observed by the observer will be (given speed of sound $= 330\,m/s$) $.............Hz$.

$A$ source of frequency $150 \, Hz$ is moving in the direction of a person with a velocity of $110 \, m/s$. The frequency heard by the person will be .... $Hz$ (speed of sound in medium $= 330 \, m/s$)

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

When a source of sound moves towards a stationary observer,the apparent frequency heard by him

Consider two sound sources $S_1$ and $S_2$ having the same frequency $100\,Hz$ and the observer $O$ located between them as shown in the figure. All three are moving with the same velocity in the same direction. The beat frequency heard by the observer is .... $Hz$.