Doppler effect with 2 sound sources

• papanik
In summary, The fly is moving at 3m/s, the bat is chasing it at 5m/s, and is emitting a sound at 50kHz. They are both moving towards a source emitting a sound at 57Hz. The frequency of the sound the fly is hearing is calculated using the Doppler effect equation and is found to be approximately 50.3kHz. The fly will also hear a sound from the source at 57.5Hz. The length of the fly is not needed in the calculations. The equation for f1 should have (v-vs) in the denominator. The frequency of the total sound may actually be 57kHz instead of 57Hz.
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

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..

Thank you

papanik said:
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?

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.

1. What is the Doppler effect?

The Doppler effect is a phenomenon where the perceived frequency of a sound wave changes depending on the relative motion between the source of the sound and the observer.

2. How does the Doppler effect work with 2 sound sources?

When there are two sound sources moving towards or away from the observer, the perceived frequency of the sound waves from each source will be different due to their relative motion. This creates an interference pattern, resulting in a beat frequency.

3. What factors affect the Doppler effect with 2 sound sources?

The speed of the sound waves, the speed of the sound sources, and the distance between the sources and the observer all affect the perceived frequency and intensity of the sound waves.

4. How can the Doppler effect with 2 sound sources be used in real life?

The Doppler effect with 2 sound sources is commonly used in radar and sonar systems to determine the velocity and location of moving objects. It is also used in medical imaging techniques such as ultrasound to measure blood flow and heart rate.

5. Can the Doppler effect with 2 sound sources be observed in everyday life?

Yes, the Doppler effect with 2 sound sources can be observed in everyday life, such as when a police siren passes by or when a train approaches and then passes by. The change in pitch of the sound is a result of the Doppler effect.

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