delsub wrote:so why is my equation not working ??

Let's try to derive it together.

When the observer doesn't have any speed in the medium, he can receive the signals of the circular frequency:

Omega = 2pi* (c/lambda)

Here 'c' is the speed of sound waves and 'lambda' is the wavelength of the 'new' wave. If we take into account the velocity of the source in the medium, we can see that:

lambda = 2pi*(c-v)/Omega0

'Omega0' is the original frequency of the source.

'v' is the speed of source with respect to the medium. Positive when (O<----S, the received wavelength is shorter since source is 'chasing' the original signal) and negative when (O S----->, the received wavelength is longer). Thus, we have:

Omega = Omega0/(1 - v/c)

We can also consider the case when the observer is moving and then get the general equation, but it is enough for our problem.