Where Does the Intensity of Sound Waves Go in Complete Silence?

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Discussion Overview

The discussion revolves around the phenomenon of sound wave intensity in the context of complete destructive interference between two speakers. Participants explore the implications of this interference on sound intensity, energy transfer, and the perception of silence.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether there would be any intensity of sound at the point of complete destructive interference and where the "lost" intensity goes.
  • Another participant explains that with complete destructive interference, the resultant wave propagation is zero, leading to silence, and argues that terms like "lost" do not apply to intensity in this context.
  • It is proposed that air particles exchange momentum and increase each other's kinetic energy at the point of interference, but whether this silence causes discomfort is subjective to the listener.
  • A later reply suggests that if the kinetic energy of air particles increases, it could lead to a slight rise in temperature in that area.
  • Some participants agree that any temperature increase would be negligible.
  • One participant humorously compares the energy from shouting over many years to the energy required to heat a cup of coffee, emphasizing the minimal temperature change in this scenario.

Areas of Agreement / Disagreement

Participants generally agree on the technical aspects of destructive interference and its implications for sound intensity, but there is some debate regarding the subjective experience of silence and the extent of temperature change.

Contextual Notes

Participants discuss the relationship between sound intensity, energy transfer, and temperature changes without resolving the implications of subjective discomfort or the exact nature of energy transfer in this scenario.

Who May Find This Useful

This discussion may be of interest to those studying acoustics, wave phenomena, or the physics of sound, as well as individuals curious about the effects of sound interference and energy transfer in physical systems.

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If we set two speakers far apart, giving identical sound waves having intensity of threshold of pain, in such a way that at midway between them, there is complete destructive interference. Would there any intensity of sound there in complete silence? If not, then where is "lost" intensity gone? Would that " silence" cause any pain?
 
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Intensity is the rate at which a wave transfers energy per unit area. If there is complete destructive interference midway between the speakers, then there will be no resultant wave propagation there, so the rate of energy transfer also equals 0(silence). Intensity is a relation between the characteristic properties of a wave (in this case power and area), and as such terms like "lost" do not apply to it in this case. Since the waves cancel each other midway, you can say that the air particles simply exchange some momentum and raise each other's kinetic energy of vibration over there. Whether that silence causes discomfort or not is entirely up to the listener.
 
Intensity is the rate at which a wave transfers energy per unit area. If there is complete destructive interference midway between the speakers, then there will be no resultant wave propagation there, so the rate of energy transfer also equals 0(silence). Intensity is a relation between the characteristic properties of a wave (in this case power and area), and as such terms like "lost" do not apply to it in this case. Since the waves cancel each other midway, you can say that the air particles simply exchange some momentum and raise each other's kinetic energy of vibration over there. Whether that silence causes discomfort or not is entirely up to the listener.
 
PWiz said:
Intensity is the rate at which a wave transfers energy per unit area. If there is complete destructive interference midway between the speakers, then there will be no resultant wave propagation there, so the rate of energy transfer also equals 0(silence). Intensity is a relation between the characteristic properties of a wave (in this case power and area), and as such terms like "lost" do not apply to it in this case. Since the waves cancel each other midway, you can say that the air particles simply exchange some momentum and raise each other's kinetic energy of vibration over there. Whether that silence causes discomfort or not is entirely up to the listener.
So if they increase each other's kinetic energy then the temperature of that area should increase! Isn't it?
 
By a negligible amount, yes.
 
PWiz said:
By a negligible amount, yes.
Thanks for clarification
 
If you shout for 8 years, the energy could heat up a cup of coffee. So you can imagine by how little the temperature will rise in this case.
 

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