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Doppler effect with 2 sound sources

  • Thread starter papanik
  • Start date
  • #1
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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

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
Hi,
Since the bat is moving towards the fly, in the equation for f1 the denominator should be (v-vs). Other than that everything is OK..
 
  • #3
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Thank you
 
  • #4
haruspex
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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?
 

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