Problem on Doppler effect and sound level

You can use the Doppler effect to find the perceived frequency, but to find the intensity level, you need to know the intensity formula and plug in all the given values. In summary, the problem requires using the Doppler effect to find the perceived frequency and then using the intensity formula to calculate the sound intensity level received by the moving observer.
  • #1
Soren4
128
2

Homework Statement


A source emits a spherical sound wave at frequency ##f=110Hz## with power ##P=1 W## in a solid angle of ##2 \pi sr##. An observer moves with velocity ##v_{oss}=108 km/h## towards the source. Determine the sound intensity level received by the moving observer.

Homework Equations


Doppler effect and sound intensity level

The Attempt at a Solution


I just do not know how to approach the problem because it is very different from a common Doppler effect problem.

The frequency perceived by the observer is ##f'=f(\frac{c+v_{oss}}{c})## but this does not give me the sound intensity level

To find the sound intensity level means to find the intensity. Now, the intensity of a sound wave is ##I= 2 \pi^2 f^2 A^2 \rho##.

Plugging ##f'## in the formula for ##I## does not give the correct result and there must be something that I am missing. How to do such exercises?
 
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  • #2
You need to define all the variables.
 

1. What is the Doppler effect and how does it relate to sound level?

The Doppler effect is a phenomenon that occurs when there is a relative motion between a source of sound and an observer. This results in a change in the perceived frequency of the sound waves, which in turn affects the perceived sound level.

2. How does the speed of the source and observer affect the Doppler effect and sound level?

The speed of the source and observer directly affects the magnitude of the Doppler effect and the perceived sound level. If the source is moving towards the observer, the frequency of the sound waves will increase, resulting in a higher perceived sound level. Conversely, if the source is moving away from the observer, the frequency will decrease, resulting in a lower perceived sound level.

3. How does the medium through which sound travels affect the Doppler effect and sound level?

The medium through which sound travels can affect the speed of sound, which in turn affects the perceived frequency and sound level due to the Doppler effect. For example, sound travels faster in solids than in gases, so the Doppler effect and sound level will be more pronounced in solid mediums.

4. Can the Doppler effect and sound level be measured and calculated?

Yes, the Doppler effect and sound level can be measured and calculated using mathematical equations that take into account the speed of the source and observer, the speed of sound, and the angle of motion between the source and observer.

5. What are some real-world applications of the Doppler effect and sound level?

The Doppler effect and sound level have many practical applications, such as in radar and sonar technology, where they are used to detect and measure the speed of moving objects. They are also important in understanding the effects of noise pollution on the environment and human health.

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