Would lots of sounds tend to cancel out?

  • Context: High School 
  • Thread starter Thread starter Freespader
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Discussion Overview

The discussion centers around the behavior of sound waves when multiple identical sounds are present, particularly focusing on whether they would cancel each other out or contribute to an overall increase in volume. The scope includes conceptual understanding of sound wave interactions and the implications of phase relationships among sound sources.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that if many identical sounds are randomly out of phase, they might cancel each other out, potentially resulting in no sound.
  • Another participant points out that when two different noise signals of equal power are combined, the volume does not double but increases by the square root of two, indicating some level of canceling out while still trending towards a louder overall sound.
  • A third participant agrees that while some sounds may cancel each other out, others in phase would reinforce one another, leading to a general increase in loudness with more sounds present.
  • A later reply introduces the concept of white noise, drawing an analogy to light and suggesting that a mix of different wavelengths leads to a specific outcome in sound as well.

Areas of Agreement / Disagreement

Participants generally agree that the presence of more sounds tends to lead to an increase in loudness, but there is contention regarding the extent to which sounds can cancel each other out and the conditions under which this occurs.

Contextual Notes

There are assumptions regarding the phase relationships of sound waves and the conditions under which they interact, which are not fully explored. The discussion does not resolve the complexities of sound wave interactions in various scenarios.

Freespader
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My understanding of sound waves is that they are waves of high and low pressure. So if there were a lot of identical sounds, but randomly out of phase, would they tend to cancel each other out, producing no sound at all? Assuming thousands or even millions of sources of these sounds. To me, it seems more intuitive that the more sounds you have the louder it would get, but I also feel like that couldn't happen.
 
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If two different noise signals of equal power are added together, the volume doesn't double, as DC voltages would, but goes up by the square root of two. So yes there is a certain amount of canceling out, but the overall trend is louder.
 
Freespader, Yes, sound waves in fluids like air, for example, are periodic pressure variations. If there are "a lot of identical sounds but (some of them) randomly out of phase" those will cancel out. At the same time there will be other waves in phase and so they would reinforce one another to make the result louder. You are correct: generally speaking, the more sounds present the louder it would be.

We cannot learn how natural mechanisms function intuitively, nor can we understand nature by how we feel about its processes. Sometimes we see experiments that demonstrate counter-intuitive results. Emotions have no place in physics. We have to use the scientific method if we are to arrive at correct understandings.
 
In addition: think about light of different wavelenghts, phases, intensities and directions of propagation. If all wavelenghts have the same probability to be present, the result is white light. In acoustic is called white noise:
http://en.wikipedia.org/wiki/White_noise
 

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