What happens when sound wave loses energy?

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Discussion Overview

The discussion revolves around the behavior of sound waves as they lose energy, particularly focusing on the changes in pressure, wavelength, and frequency. Participants explore the implications of sound absorption and the results of an experiment involving standing waves in a tube.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • A participant questions which values change when sound loses energy, specifically mentioning pressure, wavelength, and frequency, and noting an unexpected change in frequency during their experiment.
  • Another participant references a graphic from Wikipedia to illustrate the relationship between pressure and frequency, suggesting that frequency may not change with energy loss.
  • Some participants discuss the kinetic aspect of sound energy, indicating that while frequency might not be essential, it is part of the kinetic energy associated with sound.
  • There is a mention of the experimental results showing different behaviors at 500 Hz and 1000 Hz, with one participant expressing confusion over the observed differences in the graphs and questioning the consistency of the measurements.
  • Concerns are raised about the influence of external factors, such as room reflections, on the experimental results, suggesting that these could affect the measurements and interpretations.

Areas of Agreement / Disagreement

Participants express differing views on whether frequency remains constant when sound loses energy, with some suggesting it does not change while others question this assumption. The discussion remains unresolved regarding the relationship between frequency and energy loss in sound waves.

Contextual Notes

Participants acknowledge that the experimental results may be influenced by various factors, including room acoustics and measurement techniques, which could complicate the interpretation of the data.

darkmamon
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I'm a high school student doing the project about sound absorbing material
When the sound is absorbed or loses its energy which of its value will change? pressure? wavelength? or frequency?
(at first I though that the sound wave will just lose its amplitude but after the result,It look like its frequency changes too)

This is the result from my experiment(measure the standing wave in the tube)
-500 Hz frequency : http://imgur.com/2Y2jCxD
(It looks weird on this frequency.my friend said this happens because of change in frequency)
-1000 Hz requency: http://imgur.com/oRRsRm8
Thank you very much for your answer
 
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Last edited:
fresh_42 said:
Have a look on this Wiki graphic:
https://de.wikipedia.org/wiki/Lautstärke#/media/File:Akustik_db2phon.jpg
(vertical axis: pressure, horizontal axis: frequency, graphic lines: iso-volume)

The formula for energy can be found here:
https://en.wikipedia.org/wiki/Sound_energy

Note: Volume is a human "psycho-acustic" term to describe amplitude or pressure in terms of perception.

so... from what i read in your link,It looks like the frequency is irrelevant from the sound energy.
That means the sound will have the same frequency if it loses the energy?
but Why that graph happen in 500 Hz?. It's like there's a 2 kind of node in it .
The graph should look like 1000 Hz graph?
 
darkmamon said:
so... from what i read in your link,It looks like the frequency is irrelevant from the sound energy.
The kinetic part of the sound energy has particle velocity in it which again has the frequency as part of it. (I'm not saying that it is an essential part.)
That means the sound will have the same frequency if it loses the energy?
Sound is a longitudinal wave and its energy mainly determined by the pressure it puts on a surface, e.g. our eardrum.
but Why that graph happen in 500 Hz?. It's like there's a 2 kind of node in it .
The graph should look like 1000 Hz graph?
I don't find that the graphs are so much different. They both don't look optimal. Your measurement probably depends on many factors and some of them, like reflections in the room, might differ with frequency. It is impossible to tell without knowing everything about the experiment.
 

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