What Frequency Does a Worker Hear at Rest?

In summary, the worker hears a 2000Hz siren when the wind is blowing from the siren at 12m/s. The source is moving and the distance between the source and the worker changes, but the direction of the wind does not affect the frequency heard.
  • #1
ee1215
29
0

Homework Statement



2000Hz siren and worker are both at rest with respect to ground. What frequency does worker hear if the wind is blowing toward him from the siren at 12m/s?

Homework Equations



f'=f(v/v-vs)

The Attempt at a Solution



So since the worker is stationary, Vd in the numerator is 0. So the answer I got was:
2000*(343/(343-12)) = 2073Hz. Is this correct?
 
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  • #2
The air is the medium carrying the sound waves. With a steady wind of 12m/s, both the siren and the worker are moving with respect to the medium.
 
  • #3
gneill said:
The air is the medium carrying the sound waves. With a steady wind of 12m/s, both the siren and the worker are moving with respect to the medium.

not understanding how the worker is moving. If he is moving then in what direction? So I can determine + or -. I originally thought the worker was stationary which led vd to be 0 in the numerator. I see the source is moving toward the worker so the - sign is used.
 
  • #4
Does the distance between worker and source change?
 
  • #5
One way that you might look at the problem is to imagine that you shift your point of view to that of the medium itself. That is, change your frame of reference so that it is stationary with respect to the air. In that frame of reference you have a stationary medium but the source and receiver are moving. How are they moving you ask? Consult the attached figure.

As you can see, in such a frame of reference both the source and receiver are moving at the same speed and direction. The direction is opposite that of the wind direction in the "ground frame".

If you like, another way to approach the problem is to consider that the wind speed is simply added to the sound speed (for sound moving in the direction of the wind), leaving the source and receiver velocities alone (zero in this case).
 

Attachments

  • Fig1.gif
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  • #6
so, if the source and worker are stationary (zero) then the frequency heard would just be 2000Hz?
 
  • #7
Is that what your calculations show? Then it must be true!
 

Related to What Frequency Does a Worker Hear at Rest?

1. What is the range of frequencies that a worker can hear at rest?

The range of frequencies that a worker can hear at rest is typically between 20 Hz and 20,000 Hz. This range is known as the audible frequency range and is the same for most humans.

2. Can a worker hear frequencies outside of the audible range?

No, a worker cannot hear frequencies outside of the audible range. Frequencies below 20 Hz are known as infrasound and frequencies above 20,000 Hz are known as ultrasound. These frequencies are not audible to the human ear at rest.

3. What factors can affect a worker's ability to hear different frequencies?

Several factors can affect a worker's ability to hear different frequencies, including age, exposure to loud noises, and certain medical conditions. As a person ages, their ability to hear higher frequencies may decrease. Exposure to loud noises, such as on a construction site, can also damage the delicate hair cells in the inner ear and affect a worker's ability to hear certain frequencies.

4. How does the frequency of a sound affect a worker's perception of loudness?

The frequency of a sound can greatly affect a worker's perception of loudness. Generally, sounds with higher frequencies are perceived as louder than sounds with lower frequencies. This is because the human ear is more sensitive to higher frequencies.

5. Can a worker's hearing be damaged by exposure to different frequencies?

Yes, a worker's hearing can be damaged by exposure to different frequencies. Prolonged exposure to loud noises, regardless of frequency, can cause permanent damage to the hair cells in the inner ear and lead to hearing loss. It is important for workers to wear proper hearing protection when exposed to loud noises, regardless of their frequency.

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