Generate Silence: Can We Attain Total Quiet?

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Discussion Overview

The discussion revolves around the concept of generating silence through sound cancellation techniques, particularly focusing on the feasibility of creating a homogeneous sound field using two sound sources with inverse phases. Participants explore theoretical and practical aspects of sound cancellation in various environments, including rooms with moving objects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that using two sound sources with inverse phases could theoretically create silence, but this may only work at specific points, such as midway between the speakers.
  • Others argue that achieving silence in a room with moving objects complicates the situation, as sound waves may not cancel effectively due to interference.
  • A participant mentions that earphones utilizing active sound cancellation technology exist and work well for certain applications.
  • There is a discussion about the limitations of sound cancellation technology, particularly regarding the time delay in analyzing and broadcasting cancelling signals, which may prevent effective cancellation at all points.
  • Some participants reference science fiction scenarios involving machines that analyze and cancel sound waves, questioning the practicality of such concepts in real life.
  • One participant highlights that while technology like noise-cancellation headphones is real and effective for constant sounds, it cannot perfectly cancel all noise due to the nature of sound wave propagation and processing delays.

Areas of Agreement / Disagreement

Participants express a mix of agreement and disagreement regarding the effectiveness and feasibility of sound cancellation techniques. While some acknowledge the potential of such methods, others raise concerns about their practical limitations and the complexities involved.

Contextual Notes

The discussion includes assumptions about the nature of sound waves, the effectiveness of sound cancellation in dynamic environments, and the technological capabilities of current sound cancellation devices. There are unresolved questions about the ideal conditions for achieving silence.

niko2000
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Hi,
I'm wondering If we could generate homogeneous sound field and if we put two sound sources which would have inverse phaze we could attain silence.
Is it possible to do that?
Is it possible to generate homogeneous sound field in a room full of moving objects (people)?
Regards,
Niko
 
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isnt that how a muffler works?
 
n/m i misread the question
 
Yes, but that sound isn't much complex. Actually I was tinking about realizing a room with two melodies playing each in a part of room without mutual disturbance.
 
you watched batman beyond didn't you...:P

To be truthfull, I can't help you, I just couldn't resist posting though...;)
 
Theoretically, you could but only at the point exactly midway between the two speakers but nowhere else and not if there were objects between.
 
niko2000 said:
two sound sources which would have inverse phaze we could attain silence.
Is it possible to do that?
They do sell earphones that work fairly well using active sound cancelation.
 
HallsofIvy said:
Theoretically, you could but only at the point exactly midway between the two speakers but nowhere else and not if there were objects between.

You could do it at any point. The problem is making it work for all points.
 
NoTime said:
They do sell earphones that work fairly well using active sound cancelation.

I remember a science fiction in which a person built a machine that would analyze incoming sound waves and broad cast a "cancelling" signal. Of course that couldn't work. it would be already "too late" for points between the sound source and the machine and even for points further down the line, the fact that it would require some time to analyze means that the machine would not be able to cancel the sound.

In the story, teenager who were deprived of the rock and roll constantly in their ears (today, rap?) found they had to actually THINK and, of course, immediately went crazy!
 
  • #10
HallsofIvy said:
I remember a science fiction in which a person built a machine that would analyze incoming sound waves and broad cast a "cancelling" signal. Of course that couldn't work. it would be already "too late" for points between the sound source and the machine and even for points further down the line, the fact that it would require some time to analyze means that the machine would not be able to cancel the sound.

Well the machine would analyze at one end and broadcast at the other. Too bad the 'cancelling' sphere and 'actual' sphere for the sounds could never exactly match up... and you'd just end up doubling the noise.
 
  • #11
HallsofIvy said:
I remember a science fiction in which a person built a machine that would analyze incoming sound waves and broad cast a "cancelling" signal. Of course that couldn't work. it would be already "too late" for points between the sound source and the machine and even for points further down the line, the fact that it would require some time to analyze means that the machine would not be able to cancel the sound.

In the story, teenager who were deprived of the rock and roll constantly in their ears (today, rap?) found they had to actually THINK and, of course, immediately went crazy!

Thsi sounds similar to the earphones NoTime mentioned; they are no longer science fiction, and as some have been made. Last I heard, there was talk of making them standard issue for airport employees, but I don't think their use is very widesperad, ATM.
 
  • #12
Ain't technology great: Google: noice cancellation headphones? Its not star trek, guys, its for real and the technology isn't all that complicated (though its still pretty cool).

Halls - midway between the two speakers is exactly where you locate your head between headphones. Also, the speed of sound is slow compared with the processing speed of computers. No, you can't cancel out the cycle that's being analyzed, but the next one or the one after that you can. So it works great for relatively constant sounds - the primary application of this is airplanes.
First, tiny microphones, one on each earpiece, detect ambient noise before it gets to your ears. Then the noise-cancellation circuitry, usually housed in an external module, essentially inverts the captured signal, turning the noise's sound wave upside down. Before you know it, the noise-cancellation system adds the sonic opposite of the external noise to whatever you're listening to, thereby eliminating most of the pollution and leaving you with just your music.
 
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