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It is used as a citation without any real citation. — Preceding unsigned comment added by 78.162.232.188 ( talk) 14:29, 25 January 2020 (UTC)
Inverting polarity and shifting phase by 180° are not the same thing. Shifting the phase takes one cycle's worth of time. Inverting polarity is instantaneous.
-- Paclopes ( talk) 01:21, 4 May 2009 (UTC) Polarity usually refers to the polarity of ligth haves, that are described by a time varying vector field. Sound haves have no polarity. They can be described simply by the variations from the atmopheric pressure level at a given point. I am goingo to remove the references to polarity from the text.
Ideally, the noise cancellation device flips the polarity of the wave to cancel the noise. This would be the case in noise-cancelling headphones, for instance, where the electric wave can easily start from the microphone, be flipped, and travel to the speaker just in time for the acoustic wavefront to get there.
I left the phase comment in place because I imagine there are other systems where you might actually want a phase shift, if there is some kind of unavoidable delay in the system or something? But maybe it should be changed to polarity, too. - Omegatron 16:41, Apr 15, 2005 (UTC)
Let me try and summarize/summarise:
Everyone: have I sumari[zs]ed this correctly?
Atlant 13:04, 29 August 2006 (UTC)
because for us signal-processing types, phase shifting is usually interpreted as referring to each of the component frequencies.
Would a phrasing along the lines of, "...implemented by inverting the polarity of the waveform, which has the effect of altering the phase of each frequency component by 180 degrees, causing destructive interference" be acceptable to you?
ANC systems actually use both polarity inversions and phase shifting, depending on the controller strategy. There are two types of control strategies: feedback and feedforward.
- In a feedback control system, the signal you want to cancel (error signal) is fed to the controller. Commonly, a polarity inversion and some filtering are used, which may cause phase shifting. This type of strategy is the simplest one, but can only be used when the delays between the speaker and the error microphone are small; otherwise the system becomes unstable. Also, when using feedback controllers, it's not possible to cancel in the whole frecuency range, in fact there are always amplifications in some frequency bands. It can be done using analog devices.
- In a feedforward control system, a reference signal and the error signal are fed to the controller. The reference signal is correlated with the sound you want to cancel; in other words, it gives the controller information about the signal it has to cancel. The controller then uses a minimization algorithm to compute the appropriate filter so that the filtered reference signal emitted trough the speaker minimizes the error signal. In this case filters are used, which shift the phase of the reference signal. It is possible to obtain cancellation in a frequency range without causing amplifications in other bands. This strategy needs complex calculations, so a DSP or other computer system are required.
In any case, when defining the concept of destructive interference, the signals have opposite phase in a mathematical sense, regardless of how you obtain that difference of phase in practise, by inverting polarity or shifting the phase. -- Alejandroff 11:50, 19 October 2005 (UTC)
I've just removed the several comments in the article that incorrectly stated that the antinoise signal was not a phase-reversed version of the noise. I suspect the problem was that these statements were phrased too simply to be meaningful, but it's easily shown using the Fourier transform that, for those frequency bands where noise cancellation is taking place, the various frequency components of (that is, the multiple sine waves that constitute) the antinoise signal are most definitely phase-reversed from their analagous components in the noise signal; that's why destructive interference takes place. In the time domain, the antinoise is polarity reversed. In the frequency domain, it's phase-reversed (which, for a sine wave, also happens to be polarity-reversed, frequency-by-frequency).
I think this is probably too difficult to explain in the article, but if someone wants to take a crack at being bold and explaining it, please be my guest!
Atlant 12:18, 10 August 2006 (UTC)
(that is, the multiple sine waves that constitute) the antinoise signal are most definitely phase-reversed from their analagous components in the noise signal
I would like to know about the companies who can supply active noise cancellation ear defenders and also DSP based active noise controller (with adaptive algorithm or LMS- & FXLMS algorithm.
Thanks for your valuable reply.
I've removed this recently-added text from the article. To me, the description farther up in this talk page is more accurate. This newer description doesn't include the simple nearly-instantaneous, band-limited feedback mechanism that is commonly used in ANC headphones.
Shouldn't this page talk about, well, applications? Like military firing ranges, high-noise industrial areas? The first part actually seems to be talking about Types. Bihal 05:45, 28 April 2006 (UTC)
I'm curious as to whether it is (at least theoreticaly) possible to cancel the light rays of the visible spectrum through polarity reversal and/or 180° phase shift.
Could it be possible to generate a frequency that effectively cancels the phases of the ROYGBIV light rays?
And if so, then... 1.) would this create a state of total darkness?, or rather some other visible sensation? And... 2.) could such a high frequency possibly be generated with extant radio and multimedia hardware?
[It's a big question, but also one that has been nagging at me for quite some time :P ] Pine 16:20, 18 July 2007 (UTC)
Check out wave particle duality, and coherence, and interferometry. Roughly speaking, yes it is sort of possible, but only for 'short' distances. Greglocock 03:45, 21 July 2007 (UTC)
I can't see any support for the idea that sound waves have "polarity" at all—rather (mainly)) electrical signals do (as do light waves). It appears that one (but not the only) way to generate a phase-reversed wave is to invert the polarity of a signal simultaneously. Are there any references to the polarity of sound waves in the first place? Bongo matic 05:36, 3 December 2009 (UTC) hello i live nest to people that will not shut up .. i wanted to makes my computer shut them up. can i do this some how.. come on people it's 2011 —Preceding unsigned comment added by 74.215.3.182 ( talk) 21:04, 6 March 2011 (UTC)
I agree that sound waves do not have the kind of polarization (waves) that light waves have.
I hope you agree with me that rapid changes in air pressure -- above and below some average air pressure -- are perceived as sounds. Also, I hope you agree with me that if the air pressure at the ear is maintained at some extremely slowly changing or constant pressure, no sound can be heard.
When a speaker pushes out on the air in front of it, that causes the air to compress to a slightly higher-than-average air pressure. When a speaker pulls in, that causes rarefaction in the air to a slightly lower-than-average air pressure.
In this article, by "invert the polarity", we mean that (a) when some noise source causes rarefaction, the anti-noise speaker pushes out, also (b) when some noise source causes compression, the anti-noise speaker pulls in. In both cases, maintaining the air -- at the ear -- at very close to the average air pressure, so very little sound can be heard.
Is there some way other than "invert the polarity" that would be just as easy to understand and avoid the incorrect implication that sound waves have polarization (waves)?
How can we improve this article to make it easier to understand? -- DavidCary ( talk) 13:47, 16 March 2013 (UTC)
I plan on adding more theory on the physics behind Active Noise Control. Additionally I think providing more information from reliable white paper research will enhance the article. Bartscrc-NJITWILL ( talk) 01:45, 10 November 2011 (UTC)
Dumb post - Has this been used/tried for trumpets. Even the best trumpet practice mutes don't sound that good/real ( at least to me ) and the back pressure is distressing ( at least to me ). If a device could be attached... to a trumpet bell could it kill the sound in the room while I blasted away and got a more real but reduced sound in a headphone. 24.128.186.53 ( talk) 00:19, 12 February 2015 (UTC)
Another dumb question ( seeing as how this site seems to have engineers/phd;s/? on it ) - is it the difference notes, the rapid chance in notes and/or the range of notes that make this hard to do. If it was easy I suspect some manufacturer - Yamaha/Bach/etc would have done tis long ago. Why does the "initial attack phase matter"? Another dumb question - why is the "initial attack phase" different and/or a problem. Thanks 2601:181:8301:4510:A1F7:777A:2085:58A ( talk) 15:03, 30 April 2018 (UTC)
I have seen no evidence at all that this uses ANC, which would be tricky in any case. The only technical description suggests they are using masking, ie drowning out the boos with applause. Greglocock ( talk) 03:21, 12 July 2015 (UTC)
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Non ear phones, for places like apartments etc? What is the reason there are mostly only Sound Canceling Ear Phones? — Preceding unsigned comment added by 0wl ( talk • contribs) 18:20, 10 February 2017 (UTC)
Fantastic reply, Dan, thank you! — Preceding unsigned comment added by 0wl ( talk • contribs) 19:01, 10 February 2017 (UTC)
I realise without refs this cannot go into the main article, but the first time I saw an accelerometer based feedforward ANC to cancel road noise was in the late 80s at Lotus. It was fitted to a large Audi and a Porsche. I don't know if either company took it to production. Hence Hyundai's claim of a 'first' is rather inaccurate. Greglocock ( talk) 07:29, 20 February 2020 (UTC)
Need your thoughts on whether this should be a separate topic from Noise cancellation or Adaptive filtering. It appears to be someone's research material. Please help discuss at Draft:Adaptive noise cancelling#Notability for this. AngusW🐶🐶F ( bark • sniff) 18:52, 21 January 2023 (UTC)
This article is rated C-class on Wikipedia's
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It is used as a citation without any real citation. — Preceding unsigned comment added by 78.162.232.188 ( talk) 14:29, 25 January 2020 (UTC)
Inverting polarity and shifting phase by 180° are not the same thing. Shifting the phase takes one cycle's worth of time. Inverting polarity is instantaneous.
-- Paclopes ( talk) 01:21, 4 May 2009 (UTC) Polarity usually refers to the polarity of ligth haves, that are described by a time varying vector field. Sound haves have no polarity. They can be described simply by the variations from the atmopheric pressure level at a given point. I am goingo to remove the references to polarity from the text.
Ideally, the noise cancellation device flips the polarity of the wave to cancel the noise. This would be the case in noise-cancelling headphones, for instance, where the electric wave can easily start from the microphone, be flipped, and travel to the speaker just in time for the acoustic wavefront to get there.
I left the phase comment in place because I imagine there are other systems where you might actually want a phase shift, if there is some kind of unavoidable delay in the system or something? But maybe it should be changed to polarity, too. - Omegatron 16:41, Apr 15, 2005 (UTC)
Let me try and summarize/summarise:
Everyone: have I sumari[zs]ed this correctly?
Atlant 13:04, 29 August 2006 (UTC)
because for us signal-processing types, phase shifting is usually interpreted as referring to each of the component frequencies.
Would a phrasing along the lines of, "...implemented by inverting the polarity of the waveform, which has the effect of altering the phase of each frequency component by 180 degrees, causing destructive interference" be acceptable to you?
ANC systems actually use both polarity inversions and phase shifting, depending on the controller strategy. There are two types of control strategies: feedback and feedforward.
- In a feedback control system, the signal you want to cancel (error signal) is fed to the controller. Commonly, a polarity inversion and some filtering are used, which may cause phase shifting. This type of strategy is the simplest one, but can only be used when the delays between the speaker and the error microphone are small; otherwise the system becomes unstable. Also, when using feedback controllers, it's not possible to cancel in the whole frecuency range, in fact there are always amplifications in some frequency bands. It can be done using analog devices.
- In a feedforward control system, a reference signal and the error signal are fed to the controller. The reference signal is correlated with the sound you want to cancel; in other words, it gives the controller information about the signal it has to cancel. The controller then uses a minimization algorithm to compute the appropriate filter so that the filtered reference signal emitted trough the speaker minimizes the error signal. In this case filters are used, which shift the phase of the reference signal. It is possible to obtain cancellation in a frequency range without causing amplifications in other bands. This strategy needs complex calculations, so a DSP or other computer system are required.
In any case, when defining the concept of destructive interference, the signals have opposite phase in a mathematical sense, regardless of how you obtain that difference of phase in practise, by inverting polarity or shifting the phase. -- Alejandroff 11:50, 19 October 2005 (UTC)
I've just removed the several comments in the article that incorrectly stated that the antinoise signal was not a phase-reversed version of the noise. I suspect the problem was that these statements were phrased too simply to be meaningful, but it's easily shown using the Fourier transform that, for those frequency bands where noise cancellation is taking place, the various frequency components of (that is, the multiple sine waves that constitute) the antinoise signal are most definitely phase-reversed from their analagous components in the noise signal; that's why destructive interference takes place. In the time domain, the antinoise is polarity reversed. In the frequency domain, it's phase-reversed (which, for a sine wave, also happens to be polarity-reversed, frequency-by-frequency).
I think this is probably too difficult to explain in the article, but if someone wants to take a crack at being bold and explaining it, please be my guest!
Atlant 12:18, 10 August 2006 (UTC)
(that is, the multiple sine waves that constitute) the antinoise signal are most definitely phase-reversed from their analagous components in the noise signal
I would like to know about the companies who can supply active noise cancellation ear defenders and also DSP based active noise controller (with adaptive algorithm or LMS- & FXLMS algorithm.
Thanks for your valuable reply.
I've removed this recently-added text from the article. To me, the description farther up in this talk page is more accurate. This newer description doesn't include the simple nearly-instantaneous, band-limited feedback mechanism that is commonly used in ANC headphones.
Shouldn't this page talk about, well, applications? Like military firing ranges, high-noise industrial areas? The first part actually seems to be talking about Types. Bihal 05:45, 28 April 2006 (UTC)
I'm curious as to whether it is (at least theoreticaly) possible to cancel the light rays of the visible spectrum through polarity reversal and/or 180° phase shift.
Could it be possible to generate a frequency that effectively cancels the phases of the ROYGBIV light rays?
And if so, then... 1.) would this create a state of total darkness?, or rather some other visible sensation? And... 2.) could such a high frequency possibly be generated with extant radio and multimedia hardware?
[It's a big question, but also one that has been nagging at me for quite some time :P ] Pine 16:20, 18 July 2007 (UTC)
Check out wave particle duality, and coherence, and interferometry. Roughly speaking, yes it is sort of possible, but only for 'short' distances. Greglocock 03:45, 21 July 2007 (UTC)
I can't see any support for the idea that sound waves have "polarity" at all—rather (mainly)) electrical signals do (as do light waves). It appears that one (but not the only) way to generate a phase-reversed wave is to invert the polarity of a signal simultaneously. Are there any references to the polarity of sound waves in the first place? Bongo matic 05:36, 3 December 2009 (UTC) hello i live nest to people that will not shut up .. i wanted to makes my computer shut them up. can i do this some how.. come on people it's 2011 —Preceding unsigned comment added by 74.215.3.182 ( talk) 21:04, 6 March 2011 (UTC)
I agree that sound waves do not have the kind of polarization (waves) that light waves have.
I hope you agree with me that rapid changes in air pressure -- above and below some average air pressure -- are perceived as sounds. Also, I hope you agree with me that if the air pressure at the ear is maintained at some extremely slowly changing or constant pressure, no sound can be heard.
When a speaker pushes out on the air in front of it, that causes the air to compress to a slightly higher-than-average air pressure. When a speaker pulls in, that causes rarefaction in the air to a slightly lower-than-average air pressure.
In this article, by "invert the polarity", we mean that (a) when some noise source causes rarefaction, the anti-noise speaker pushes out, also (b) when some noise source causes compression, the anti-noise speaker pulls in. In both cases, maintaining the air -- at the ear -- at very close to the average air pressure, so very little sound can be heard.
Is there some way other than "invert the polarity" that would be just as easy to understand and avoid the incorrect implication that sound waves have polarization (waves)?
How can we improve this article to make it easier to understand? -- DavidCary ( talk) 13:47, 16 March 2013 (UTC)
I plan on adding more theory on the physics behind Active Noise Control. Additionally I think providing more information from reliable white paper research will enhance the article. Bartscrc-NJITWILL ( talk) 01:45, 10 November 2011 (UTC)
Dumb post - Has this been used/tried for trumpets. Even the best trumpet practice mutes don't sound that good/real ( at least to me ) and the back pressure is distressing ( at least to me ). If a device could be attached... to a trumpet bell could it kill the sound in the room while I blasted away and got a more real but reduced sound in a headphone. 24.128.186.53 ( talk) 00:19, 12 February 2015 (UTC)
Another dumb question ( seeing as how this site seems to have engineers/phd;s/? on it ) - is it the difference notes, the rapid chance in notes and/or the range of notes that make this hard to do. If it was easy I suspect some manufacturer - Yamaha/Bach/etc would have done tis long ago. Why does the "initial attack phase matter"? Another dumb question - why is the "initial attack phase" different and/or a problem. Thanks 2601:181:8301:4510:A1F7:777A:2085:58A ( talk) 15:03, 30 April 2018 (UTC)
I have seen no evidence at all that this uses ANC, which would be tricky in any case. The only technical description suggests they are using masking, ie drowning out the boos with applause. Greglocock ( talk) 03:21, 12 July 2015 (UTC)
Hello fellow Wikipedians,
I have just modified 3 external links on Active noise control. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
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After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than
regular verification using the archive tool instructions below. Editors
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(last update: 5 June 2024).
Cheers.— InternetArchiveBot ( Report bug) 17:43, 3 October 2016 (UTC)
Non ear phones, for places like apartments etc? What is the reason there are mostly only Sound Canceling Ear Phones? — Preceding unsigned comment added by 0wl ( talk • contribs) 18:20, 10 February 2017 (UTC)
Fantastic reply, Dan, thank you! — Preceding unsigned comment added by 0wl ( talk • contribs) 19:01, 10 February 2017 (UTC)
I realise without refs this cannot go into the main article, but the first time I saw an accelerometer based feedforward ANC to cancel road noise was in the late 80s at Lotus. It was fitted to a large Audi and a Porsche. I don't know if either company took it to production. Hence Hyundai's claim of a 'first' is rather inaccurate. Greglocock ( talk) 07:29, 20 February 2020 (UTC)
Need your thoughts on whether this should be a separate topic from Noise cancellation or Adaptive filtering. It appears to be someone's research material. Please help discuss at Draft:Adaptive noise cancelling#Notability for this. AngusW🐶🐶F ( bark • sniff) 18:52, 21 January 2023 (UTC)