Doppler effect with 2 sound sources

[papanik]

Homework Statement

A fly is moving with a speed vl=3m/s and a bat is chasing it with vs=5m/s. The bat is emitting a sound with fs=50kHz. They are moving on the same line towards point C which is a source emitting a sound at f'=57Hz. Find the frequency of the total sound the fly is hearing. The fly has a length of 2mm.

Homework Equations

Doppler effect equation

The Attempt at a Solution

The fly is hearing from the bat a sound at a frequency f1=(v-vl)*fs/(v+vs)=50.3kHz approximately
The fly is also hearing a sound from source C f2=(v+vl)*f'/v=57.5Hz
where v=343m/s speed of sound
The frequency of the sound the bat is emitting is not influenced by source C and vice versa.
Since f1>>f2 the fly will hear two different sounds with discrete frequency
The length of the fly i assume that it is not needed in the calculations

 

[Abhilash H N]

Hi,
Since the bat is moving towards the fly, in the equation for f₁ the denominator should be (v-v_s). Other than that everything is OK..

 

[papanik]

Thank you

 

[haruspex]

They are moving on the same line towards point C which is a source emitting a sound at f'=57Hz. Find the frequency of the total sound the fly is hearing.

Are you sure that's not 57kHz?

 

[Nickie]

as it is not mentioned in the equations. However, the length of the fly may affect the intensity of the sound it receives. Additionally, the direction and distance of the fly from the bat and source C may also affect the perceived frequency. It would be helpful to have more information and a diagram to accurately calculate the frequency of the total sound the fly is hearing.
Moreover, the calculations assume that the fly is stationary, which may not be the case as it is moving with a speed of 3m/s. This could also affect the perceived frequency. Further experiments and measurements would be needed to accurately determine the frequency the fly is hearing.