Talk:Noise-cancelling headphones

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New Picture[edit]

I feel the current photo doesn't do justice to the article. The best noise cancelling earphones are the "monitor"-style ones, which completely surround the ear and actively fade external sounds. The current photo shows a picture of in-ear earphones, which cannot come close in terms of noise cancelling to monitor style earphones. I feel the article needs a better quality image so I'm replacing it with a shot of my own headphones, tell me what you think... Feel free to voice any objections, etc.. here

Gamer112 (talk) 09:22, 22 April 2008 (UTC)

I think there's room for more than one photo. Binksternet (talk) 10:21, 22 April 2008 (UTC)
The photo provided by Gamer112 is of TDK ST200 headphones, which are a passive, noise-isolating model (not noise-canceling). This pic should probably be replaced.Cheakamus (talk) 16:35, 27 December 2011 (UTC)

Do They Cause Damage[edit]

I know that noise cancelling headphones just add another wavelength inverted to your ear, so would listening to a noise cancelled sound at 120+ decibels cause hearing damage? What about the extra pressure caused by noise cancelling headphones.. anyone?

I've wondered that, too. I think my more simply-designed, generic brand headphones just drown out outside noise with loud, lower-frequency white noise. It seems to me like that could potentially cause as much damage as turning up the volume with normal headphones to drown out outside noise. Also, the noise clearly affects my inner ear, because if I repeatedly switch the headphones on and off, I experience slight dizziness. Tyharvey313
The whole point of noise-cancelling headphones is that, at your eardrum, the noise + antinoise sums to as near zero as the technology will permit. This makes noise-cancelling headphones useful as hearing protection in loud environments (although they're probably not effective nor certified as protection against single, loud, percussive events such as gunfire).
Here's a brief reference that actually makes the claim of hearing protection: [1]
Atlant 13:01, 12 April 2006 (UTC)
So, I will hear the gun fire and cough? --Alex Blokha 16:36, 22 October 2007 (UTC)
But see, mine don't respond to outside noise, they just always produce loud white noise around a certain constant frequency. Couldn't that be harmful? Tyharvey313 22:39, 18 April 2006 (UTC)
If it's white noise, it's not "around a certain constant frequency". But that's just a nit. ;-)
Seriously, if your noise-cancelling headphones are putting out either a lot of white noise or some constant tones (frequencies), they're broken. The worst you should hear is a little hiss (white noise) well below the typical "program level" you'd expectthe headphones to reproduce. As I mentioned in the article, my experience with the Bose headphones is they introduced no perceivable background noise or tones while my Sony headphones introduce slight white noise.
Atlant 14:06, 31 May 2006 (UTC)
As a daily NC headphones user I'd say it is likely that they are healthier than regular phones since there's a tendency not to raise the volume so high with them.

Perhaps not entirely on topic, but these noise-reducing headphones ravaged my eardrums today, setting up some kind of high pitched magnetic feedback ressonance that could be heard across the entire office - directly into my ear. https://www.dropbox.com/s/5modr0raso4knjy/VIDEO0147.mp4?dl=0 Psicoma — Preceding undated comment added 14:54, 20 April 2015 (UTC)

Insulating Headphones[edit]

I think, perhaps, the information on insulating headphones should be moved to a different article. Am not sure they are normally called 'Noise-cancelling headphones'. I may well be wrong here, though Andrewferrier 22:57, 2004 Dec 30 (UTC)

Definitely. Unless we add another section here stating that there is a difference between active and passive noise-cancelling, there's bound to be a lot of confusion. --@@ron 08:55, 18 November 2006 (UTC)

Audible Counter-Noise?[edit]

Will people beside you hear the counter-noise generated by your earphone? -- Toytoy 01:48, Jan 27, 2005 (UTC)
It depends on the headphone design. In principle, at the ears of a third party, the counter-noise wouldn't be well phase-correlated with real noise so the counter-noise ought to be heard at their ears (although I'd imagine the perception of it would be weird since lower frequencies of the counter-noise would be better phase-correlated with the real noise than high frequencies of the counter-noise). But in practice, the noise-cancelling earphones I've seen are "closed-ear" systems that attempt to also use passive means to keep as much outside noise "out" as possible, and in so doing, they tend to also keep the counter-noise "in". Regardless, if I switch on my Sony's and just hold them out in free-space, I've never really perceived them as making any sound, but now that you asked, I'll pay more attention :-) .
Atlant 13:35, 27 Jan 2005 (UTC)
At first I was making a much more miserable picture in my mind. Since bass is not filtered by the ear mask in a Boss-type closed headphone, I expect the counter-noise would leak. Other people would suffer. If you've been sitting behind a speaker, you'll know a speaker would sound a little differently from its back (unfocused, dampened and distorted by the speaker's material). You push the air forward, you suck in the air in the behind and vice versa. If the reverse-directional counter-noise leaks, people may hear it. And it will be totally out of sync. Possibly someone somewhere would hear a louder noise occassionally.
As to the Sony-type earbud, there is no ear mask to filter the counter-noise. It could be even worse.
Then why don't you observe it?
Fact: I think the reason you don't hear it, is because the counter-noise is so weak, you can't hear it a few inches away. The counter-noise generated for each ear does not need to combat Boeing 747's four powerful turbofan engines. It only needs to generate so much focused noise to keep an ear drum from popping out. The distance from the earpiece to your ear drum is possibly 3 to 4 cm. If you're 8 cm away, you hear about the same background noise plus less than 1/4 of out of sync and distorted counter-noise. If you're a few steps away, you hear the background noise and nothing else. (I don't have a noise-cancelling earphone. I can't experiment.) You just don't sleep on other people's earphone cover.
The primary reason other people don't hear the "counter/anti-" noise is because the sound generated by the headphones is specifically designed to cancel out the ambient noise that has made it into the headphone. The wave forms of the intruding ambient sound and the counter-noise cancel out and there is none for other people to hear. Of course, the process is not perfect and cancellation isn't either, so there will be some leakage. As you note, Toytoy, the signal is indeed intrinsically weak, but it is also merely the "leftover" sound from imperfect cancellation - which will be just a small part of the original (weak) signal. Ossipewsk 01:55, 30 April 2007 (UTC)
If it's your earphone; it works. If you try to make your car less noisy ... I think people on the street would throw rocks at you! -- Toytoy 06:42, Jan 28, 2005 (UTC)

Real-world performance of noise-cancelling headphones[edit]

By the way, how good is your Sony earphone? Is that the $150 MDR-NC11? Does it work in a 747? Does it work against crying kids? (Guess not, kids are not crying in bass. They are six-mile-high devils.) -- Toytoy 06:42, Jan 28, 2005 (UTC)

I have the MDR-NC20 "over-ear" style headphones. They are generally effective but they're not magic. Their cancelling is confined to the bass and low-midrange frequencies and they depend on the usual passive isolation for higher frequencies.

In casual A-B listening tests, I found their cancellation to be very similar to the much-more expensive Bose QuietComfort-II phones, BUT:

The Sony phones have two defects:

  1. They introduce some background hiss; the Bose phones did not seem to do this.
  2. In an environment with fast air pressure changes (as I experience riding on a bus as the bus flexes as a result of road shocks), the headphone amplifiers frankly overload. With minor pressure changes and minor overloading, this leads to "picket fencing" of the noise cancellation. With larger pressure changes (as the bus hits a hole in the road) this leads to complete wipe-out of the sound. I haven't had a chance to take the Bose phones on the bus yet, so I can't say whether they suffer from the same defect. This defect is *NOT* apparent on airplanes, by the way, where the Sony headphones were very pleasant.

Neither the Bose nor the Sony 'phones block much speech, cell phone ringtones, etc.

Atlant 14:23, 28 Jan 2005 (UTC)

Speed-of-sound considerations[edit]

Another question? Cabin pressure in an airlinear is about 0.75 ATM (8,000 ft). The speed of sound changes a little because of lowered pressure (temperature remains at room temprature). I don't have time to do math. I guess it does not affect the earphone by much. -- Toytoy 06:42, Jan 28, 2005 (UTC)

Remember, the wavelengths of the frequencies that are being actively cancelled are quite long compared to the distances within the headphone earcups; a small change in the speed-of-sound probably has no noticeable effect. Atlant 14:23, 28 Jan 2005 (UTC)

Change in pressure has a negligible effect on the speed of sound in air. —The preceding unsigned comment was added by 68.150.245.120 (talkcontribs) .

Teachers[edit]

Papabrow added:

  • Teachers let their students use this as a means of study.

What did you mean by that ? (reverting for now) Taw 09:18, 4 February 2006 (UTC)

"Opposite polarity" versus "180 degrees out of phase"[edit]

Just for the benefit of folks who are editing the article and/or debating this point:

You realize there's no difference in these two statements, right? While I, myself, tend to like the new "opposite polarity" phrase better (because it has a sort of immediate understandability), if you think about the Fourier transform and signals in the frequency domain instead of in the time domain, you'll see that a signal of the "opposite polarity" has all of its component frequencies shifted by 180 degrees compared to the reference signal.

So both versions of the statement are equally correct ;-) .

Atlant 14:12, 31 May 2006 (UTC)

Um, no. There is no such thing as phase, in the time domain. You have to make some assumptions for it to become meaningful. Reversing polarity is as simple as swapping two wires. That requires no assumptions. Greglocock 10:24, 22 February 2007 (UTC)

It might seem like they're both correct at first but with active noise cancelling it is only "opposite polarity" that is correct. I don't really have time to explain it, just throwing my opinion in here =) 78.82.141.50 (talk) 06:06, 20 June 2009 (UTC)

Spelling[edit]

This article is all over the place with "canceling" vs. "cancelling". The title differs from the first sentence, and both forms appear again and again within the article. Shouldn't we settle upon one way within the one article? -Chinju 18:19, 10 August 2006 (UTC)

Microsoft Word says it's "canceling" so please feel free to be bold and fix all the wrong ones.
Atlant 18:29, 10 August 2006 (UTC)
Well, there is legitimate room for disagreement. As I understand it, this is one of those differences Noah Webster initiated between American English and British English. Though the advice to be bold is good; I think I will turn all the forms into "cancelling", to match the title. -Chinju 17:37, 12 August 2006 (UTC)
See Wikipedia:Manual of Style#National varieties of Englishjammycakes 10:43, 21 November 2006 (UTC)
The title is also in conflict with other wikipedia pages, such as [|Noise-Canceling Microphone]. The spelling of cancelling or canceling is based on either using British English or American English respectively. Does wiki have a standard for article titles?

"poorly adjusted"[edit]

The article states: "A common example of poorly adjusted noise cancellation is the Bose QuietComfort series of headphones, although other manufacturers including Sony/Aiwa also make noise-canceling headphones. These are by no means all or the best engineers at headphone noise cancellation."

In addition to the bad grammar (perhaps the original writer isn't fluent in English?), what is meant by "poorly adjusted"? Without a reference, it comes across as Bose-bashing. For example, what would be an example of a noise-canceling headphone that this properly adjusted? While it may be desirable to have a noise-canceling headphone that used sound cancellation across the entire spectrum, it's just not practical or cost-effective given today's technology - it like saying that automobiles that get 50 miles/gallon aren't "properly adjusted" because they don't get 400 miles/gallon.

I'm temped to remove/rewrite these sentences, but I would like to give others a chance to weigh in first. Anechoic Man 22:14, 1 October 2006 (UTC)

Be bold. It's a blatant review / opinion. There, it's gone. -- Rogerborg 15:21, 4 October 2006 (UTC)

List of models of noise-cancelling headphones[edit]

According to the Sony Web site (at least what comes up when accessed from the USA) lists the model MDR-NC6. Is that the same thing as the NC-6 that appears in the list? I don't have time to research it, myself. Perhaps there is potential confusion with the model numbers of products, and the countries in which they are offered. TJKluegel 01:42, 20 December 2006 (UTC)

Passive vs active noise cancelling[edit]

This article only lists active noise cancelling headphones. What about passive (in-ear) noise cancelling headphones such as the sure e series - http://www.shure.com/PersonalAudio/ComparisonCharts/us_pa_comp_char_earphones or etymotic er6 - http://www.etymotic.com/ephp/er6.aspx

There's no such thing as "passive noise cancelling". The passive techniques are simply "noise absorbing" or "noise blocking"; you'll notice Shure refers to them as "noise isolating". None of those techniques are the subject of this article.
Atlant 23:05, 28 December 2006 (UTC)
Could someone who knows the market PLEASE REMOVE all the passive in-ear headphones that have been spammed into the list?
Atlant 15:11, 15 January 2007 (UTC)


Shame on all of you. Information is key, suggestions are not Spam (misinformed or not).
It is an often asked question, and perhaps the article should mention it ("Noise isolating headphones, often called/mistaken as passive canceling headphones...")

66.172.101.250 (talk) 03:06, 22 February 2010 (UTC)
How about a separate article on 'Noise Isolation?' Halofanatic333 (talk) 14:18, 21 May 2010 (UTC)

Bulkiness and other disadvantages[edit]

I removed the disadvantage point "They are generally more bulky than traditional headphones" - this is generally no longer the case, if it ever was.

I also added a couple of {{Fact}} tags, as some of those claims need backing up.Ossipewsk 02:08, 29 January 2007 (UTC)

I've reverted these edits. Most of the disadvantages cited are not "possible" disadvantages, they are sure, certain disadvantages and are a function of the physics of the system. For example, active noise cancellation requires power, no ifs, ands, or buts about it. Power sources require volume, so even if the microphones and amplifiers required no volume at all, the power source (typically, a battery) does.
Atlant 13:12, 29 January 2007 (UTC)
I don't want to re-revert you, as you are a class contributor - so I'd really like you to reconsider. Looking at retail noise-cancelling (NC) headphones you'll find that NC headphones are generally not bulkier than similar-price/quality non-NC headphones. I agree, there is the added weight of an AAA or AA battery and the NC-system bits and pieces - about 20g in all. Most NC headphones (the well-designed ones, anyway ;-) now incorporate these into the head-piece (or whatever the bit joining the ear-pieces is called) or into existing space in the ear-pieces, thus the extra bulk is minimal at most.
Can we leave in the "citation needed" tags regarding "low-frequency pressure waves" and for "stray electromagnetic fields", please? These are assertions that really should be referenced.
Cheers, Ossipewsk 23:52, 29 January 2007 (UTC)

Driving with headphones[edit]

Is noise-cancelling headphones safe to use for driving? Regular headphones block out all noise, but noise-cancelling headphones should only block road, engine and wind noise. Right?
"Regular headphones block out all noise"
No. They may reduce all frequencies more equally, but you don't get silence. Only low+mid frequencies can be actively cancelled, so NC headphones have at least as much noise absorption as normal, to remove the high treble noise as well.
However, back to your question - being aware of your surroundings is quite fundamental to road safety. Horns, engine defects, revs, approaching vehicles, sirens, crossing signals, indicators ticking, yelling pedestrians, hitting cats-eyes, rumble-strips, non-skid surfaces at junctions, silence when a wet road becomes an icy road ...
--195.137.93.171 (talk) 17:32, 10 December 2011 (UTC)

History section[edit]

Is it just me or does that section seem to be a thinly-veiled commercial? If so, it would violate NPOV. I await other opinions. AarrowOM 17:40, 16 October 2007 (UTC)

Yes, the wording does indeed remind you of a commercial. -- Anders. 26/1-2009 —Preceding unsigned comment added by 130.226.87.164 (talk) 12:55, 26 January 2009 (UTC)

Digital Noise Cancelling Headphones[edit]

Disclosure: I work for Sony Europe's online public relations agency, immediate future. We are committed to working within Wikipedia's guidelines for PR companies.

The article states that most noise cancelling headphones use analog technology, but Sony's MDR-NC500D headphones do use digital technology. To the best of our knowledge, they are the only digital noise cancelling headphones currently available. (http://reviews.cnet.com/headphones/sony-mdr-nc500d-digital/4505-7877_7-32854241.html)

Would it be possible for the article to reflect this? Or even to add a new section explaining the difference between digital and analog noise cancelling technology? We have produced the following suggested text to explain the difference:

"Digital noise cancelling headphones use digital signal processing technology to reduce unwanted background noise and improve audio reproduction quality. Conventional noise cancelling headphones use only analogue technology.

The performance of noise cancelling headphones is heavily dependent on the efficiency of the noise cancelling filter circuit that sits between the noise detection microphone (usually positioned on the outside of the ear cup) and the speaker driver which generates the required ‘anti-noise’ wave. In digital noise cancelling headphones the noise cancelling filter is a piece of software running on a DSP (digital signal processor) chip, rather than a simple electronic circuit.

Although digital noise cancelling headphones use the same basic principle of reducing unwanted ambient noise the DSP enables digital noise cancelling headphones to create an opposite polarity sound wave which more closely matches the ambient noise present and therefore achieve better levels of noise reduction.

While conventional noise cancelling headphones are configured with a single noise filter profile that cannot be altered, since it is hardwired into an electronic circuit, digital noise cancelling headphones can alter their noise filter profile through software in order to allow for a better match to different noise environments, such as an aircraft, train or busy office.

One of the key limitations of conventional noise cancelling headphones is that the noise cancelling circuit degrades the quality of the audio signal sent from the MP3 player or in-flight entertainment system, resulting in distortion and background hiss. Digital noise cancelling headphones reduce this problem with the inclusion of a software equaliser, also running on the DSP chip, to clean up the signal and improve the overall quality of audio produced by the headphones. Overall, Digital Noise cancelling headphones produce better fidelity sound than their analogue counterparts."

Lance.

Lconcannon (talk) 15:20, 12 March 2009 (UTC)

Too much of what you've written is unsupported by white papers and unquantified. How much less distortion does the product have? At what frequencies and sound pressures?
Unmentioned in the above text is the amount of latency. How much latency is present? How does that affect the construction of the opposite polarity signal, especially for low frequencies that can penetrate the shell of the headphones? What about reports of the MDR-500D distorting on bass notes at high volume? What about short battery life? Why does the product not have two microphones, one on each ear cup, for a DSP-based comparison?
I'm a big fan of DSP-based audio electronics (I use DSP all the time in my work in live sound) but the text you offer appears short on hard facts. I do see the value to the reader of having a paragraph or two about digital noise canceling technology, but I wouldn't quote your text in its entirety. Binksternet (talk) 16:49, 12 March 2009 (UTC)

Phase versus polarity[edit]

Polarity is only correct for the electrical signal. For the sound wave, it is phase. See the patents referenced in the Active noise control article, three of which reference "phase" and none of which references "polarity":

Please do not revert without references. Bongomatic 04:42, 3 December 2009 (UTC)

Phase is less correct than Polarity, I am sure this has been discussed in the talk for that article. I do not know if a patent is an RS. I am not going to indulge in stupid wiki games but I worked on antinoise systems for 2 years and in acoustics for much longer. Greglocock (talk) 05:16, 3 December 2009 (UTC)
Great. You're obviously an expert and I certainly am not. Can you please provide references? I hope you don't consider observance of WP:V to be a "stupid wiki game". Bongomatic 05:25, 3 December 2009 (UTC)
Again, I am not an expert, but a cursory search of Google Scholar (not a perfect source, for sure) suggests that sound waves don't have polarity at all. Rather, electric signals do, and reversing the polarity of an electric signal results in a sound wave of opposite phase being generated by a speaker. So if the article suggested that the phase of the sound wave was the result of a polarity reversal in the electric signal, that would be supported by what I have seen. Bongomatic 05:33, 3 December 2009 (UTC)


Thanks for mentioning references. They are quite important to an article's reliability and verifiability, but in this section of the article there are none, so neither you nor I can assume the higher ground relative to the words phase and polarity.
Regarding your list of refs, patent writers aren't always known for their precision in English usage. Precision in language is ideal, of course, but not always achieved. In this patent you indicate, the author uses the phrase "opposite phase." There is no such thing as opposite phase but there is most certainly opposite polarity.
People skilled in English usage who have written specifically to the employment of these terms in pro audio agree that phase is dependent on time of arrival whereas polarity is not. If a noise canceling circuit shifts the phase by a certain amount of time or by a certain number of degrees of phase rotation, the cancellation will occur at the target frequency. Frequencies on either side of the target will be reinforced and canceled in an alternating fashion akin to comb filtering. A 180° phase shift is thus frequency dependent. A polarity reversal, however, affects all frequencies together.
It is likely that some noise canceling circuits employ a bit of time-based phase shifting, but none can operate without polarity reversal. Binksternet (talk) 05:41, 3 December 2009 (UTC)
Interestingly, the definition of polarity in the glossary provided only applies to electromagnetic waves. I think the confusion here is that "opposite phase" does not imply "phase shifted", despite the suggestion of that in the first reference and your comments.
You can satisfy yourself of this by simply looking at the results of a Google Scholar search for 'sound "phase inversion"'.
I understand fully the difference between inversion and shifting detailed in the first link, but that doesn't justify the use of the term "polarity" where there is no evidence that there is a consensus view of scientists that "polarity" can be used to apply to pressure waves. Bongomatic 06:54, 3 December 2009 (UTC)
Inversion is probably a better expression than reverse polarity, but either is better than anything that mentions phase. You are right, in the two acoustic texts (Beranek, White&Walker) I have to hand neither mentions that a positive sound pressure is regarded as positive. Funny that. The equations seem to take it as read. The fundamental problem is that you are thinking in the frequency domain, I doubt any headphone bothers with that. There is an intrinsic problem with using frequency domain stuff to actively modify sound signals, I am sure you understand why. Greglocock (talk) 08:51, 3 December 2009 (UTC)
You ask us to search Google Scholar for the term "phase inversion", but I will not be doing that. Why would I search for the incorrect usage when we all know that we will find people out there making the mistake that was announced by the guys at Rane? They wrote, "We wrongly say something is out-of-phase when we mean it is inverted..." and I believe if we search for any number of wrong terms, we will find them. Instead of all the wrong searching, I propose that we use Google Books and Google Scholar to search for the correct usages, and use those as references. Here are three examples:
  • Maximum PC magazine, September 2005. Reviews. "AKG K 28 Noise Reducing Headphones."

    "Tiny microphones on each closed-back earphone monitor ambient noise and send the low-frequency signals they pick up to a small module you can clip on your belt. Turn on the module and it reverses the polarity of these signals to generate a mirror-image signal, which it then pipes back to the headphones to cancel the waveform of the ambient noise."

  • US Patent Application 20090010474: Headphones.

    "The noise-canceling headphones are equipped with: a microphone installed in a housing to receive ambient noise components generated around the headphones; and noise-reducing circuitry to generate signals with the opposite polarity of the ambient noise components, combine the opposite-polarity signals with audio signals, and output the combined signals through speakers. The noise-canceling headphones are thus active headphones that make listeners feel that noises are reduced with “opposite-polarity cancellation effects” to the ambient noises.
    Another type of known noise-canceling headphones is equipped with: a microphone provided between an ear of a user and a speaker to directly receive sounds that include ambient noises components and are to be given off to the ear; and feedback noise-reducing circuitry to detect the ambient noises components from the difference between the received sounds and an original signal and output audio signals from which the ambient noises components are subtracted, thus reducing the ambient noises components.
    The former using the opposite-polarity cancellation effects is called a feed forward type whereas the latter using the feedback circuitry is called feedback type."

Those are pretty good usages of the term to describe the technology. Especially interesting is the naming of feed forward and feedback types. Binksternet (talk) 22:20, 3 December 2009 (UTC)
Those references all talk about signals. Most explicitly refer to the signal being subsequently transformed into an audio wave, so they are talking about the signal in electrical form. As mentioned below, it is clearly accurate and worth mentioning that the inverted-phase sound wave is generated by driving a speaker with a reversed polarity electrical signal. Bongomatic 22:45, 3 December 2009 (UTC)

<==In noise canceling headphones, the noise canceling is achieved via electronic circuitry, not acoustically. There are no noise canceling designs that use multiple drivers with varying signals, all aimed at the same ear. In this case, the polarity change is applied to the ambient microphone signal at the time that it is summed with the desired playback signal. There may as well be phase shifts, all-pass filtering, delay circuitry, etc., but polarity reversal is the key, and it happens electronically before the headphone drivers change fluctuating electrical signals to sound waves. Binksternet (talk) 21:52, 3 December 2009 (UTC)

Yes that's surely true. However, the sentence in question refers not to the electrical circuitry and signal, but to the sound itself—which does not have any polarity (only phase) by normal definitions:
"electronic circuitry which generates an "antinoise" sound wave with the opposite [disputed word] of the sound wave arriving at the microphone." (emphasis added)
To explain that this is achieved by reversing the polarity of an electrical signal, rather than other signal processing techniques, would seem to be useful and relevant. To incorrectly refer to the "polarity" of a sound wave would not. Bongomatic 22:10, 3 December 2009 (UTC)

Suppose the incidient sound has an instantaneous amplitude of 1 Pa. What does our antinoise system have to generate to eliminate it? A signal with an amplitude at the same time of -1 Pa. No phase, no nothing else, is required. Phase is a frequency domain property, real signals (whetehr sound pressure or electrical) occur in the time domain. Greglocock (talk) 00:07, 4 December 2009 (UTC)

Even assuming there is agreement on what "-" means and and that it is the appropriate notation, it doesn't mean that the transform is referred to in the literature as a reversal or inversion of "polarity" as opposed to "phase". You might think that "phase" ought not to be used for opposite amplitude, but in fact the phrase "opposite phase" is frequently used to apply to sound waves in the literature, and the phrase "opposite polarity" or "inverted polarity" is not.
Your view that (relative to a base pressure) that opposite pressure variations should be referred to as "polar" opposites has an attractive logic to it. However, other than possibly in the specialized audiophile community, that usage does not seem to be common, while referring to such opposites as "phase inverted" or as of "opposite phase" does seem to be common.
This is not a logical exercise, but a linguistic one. See WP:MOS#Follow the sources for the guideline for usage in Wikipedia. This is not a soapbox for using the terminology that you wish would be widely adopted. Bongomatic 02:04, 4 December 2009 (UTC)
Actually I am a professional engineer who spent 15 years measuring and analysing noise and vibration, before moving on to more interesting things. The two texts I consulted are professional textbooks about acoustics (Beranek, White&walker). Nothing to do with audiophiles /at all/. You are wrong, if your references agree with you then they are wrong. Sorry about that, but it is quite common for the general public to get confused about technicalities. I can assure you that a positive pressure has a very real meaning, not arbitrary in the least. Your obsession with (sine?)waves is leading you astray, real, multifrequency, waveforms do not have phase in any useful sense in the time domain. In summary it doesn't matter how many paragraphs you write, or how many incorrect references you pull up, you are wrong. Greglocock (talk) 03:08, 4 December 2009 (UTC)
You point us to WP:MOS#Follow the sources but you may have noticed that the sources currently in the article do not mention phase or polarity at all and that the sources we all have been pointing to here on the talk page have a split between those which incorrectly use phase when they mean polarity and those which use polarity correctly. When faced with a choice of sources, why ever would we wish to choose the wrong ones?
Phase is relative: it is measured in degrees or time. There is no sense of "opposite" in time. In degrees, the sense of "opposite" falls apart when you consider 180° has the same steady state mix results as 540°, 900°, -180°, etc. Which of those is supposed to be "opposite"—all of them? The phrase "opposite phase" when it appears is always wrong and misused—if some signal is 180° out of phase with another thing then the two will not cancel out completely. There will be an audible blip at the beginning and end of the blended signals, and frequencies away from the target frequency will show comb filtering, not canceling. Binksternet (talk) 04:04, 4 December 2009 (UTC)
You earlier said that the two textbooks you referenced did not mention positive in regards to pressure (relative to ambient, I assume, as there's nothing less than zero absolute pressure, I think) pressure. But so what either way? The question here is whether the word "polarity" is conventionally used to describe sound waves. You could agree that positives and negatives, inversions (usually used to refer to 1/x) or opposites (usually used to refer to -x) are all appropriate descriptive terms, and none of those choices would necessitate nor even suggest the use of the term "polarity". That is a word that means different things in different contexts, and it is clear that there is no consensus usage of the term as applied to sound waves.
What is clear is that the term "phase inverted" or "opposite phase" is used to denote pressure of -x at the same time, with no time shift whatsoever.
You may think that this notation is misleading, or inconsistent, or otherwise regrettable, but every relevant search I could come up with (in the web, in Google Scholar, or Google Books) shows a massive preponderance of the (possibly mis-) use of the term "phase" for inverted pressure waves. Bongomatic 04:57, 4 December 2009 (UTC)
Why do you keep talking about pressure waves, polarity in sound waves and absolute polarity? None of those terms are relevant to ANC headphones which flip the polarity in the electronics, then send that signal to the speaker driver along with the desired signal. The ANC headphones also use other techie tricks, but all of them flip the polarity of the processed microphone signal before it is fed to the speaker driver.
You might want to sort your references relative to how old they are. The older ones are more likely to use imprecise language. I'm a veteran live sound engineer, so I know that in live sound, the correction from the old Greek letter phi indicating so-called phase reversal on a mixing console began in the late 1990s. Carey Davies, mixing console designer at Allen & Heath, wrote in 2000 that his company was just then getting away from writing "phase" in the user manuals when "polarity" was meant. The realization that the industry was using the word "phase" in a sloppy and imprecise manner can be pinned somewhere near the 1999 white paper written by Chuck McGregor, who went on to lead the technical services department at Eastern Acoustic Works and then to become and independent consultant. Binksternet (talk) 05:27, 4 December 2009 (UTC)
Your google fu is weak. Try compression wave, and positive, as search items, or rarefaction wave and negative. Not surprisingly if you search for phase you'll get phase related hits. For a brief example why we "know" that positive pressure is meaningful read up and understand Acoustic Intensity. If positive pressure was rarefaction then you would be able to listen to your curtains as the loudspeaker draws music out of them.Greglocock (talk) 00:06, 5 December 2009 (UTC)
What does the use of the term "positive" or "negative" demonstrate about the use of the term "polarity"? Bongomatic 01:32, 5 December 2009 (UTC)
Well yesterday you seemed to be worrying about whether "-" had any physical meaning for pressures. It seems rather difficult to talk about polarity without talking about + and -. Greglocock (talk) 05:22, 5 December 2009 (UTC)
You would do well to avoid inferences about what other people worry about.
Tremble tremble. Are you going to burst into tears? or stamp your foot, crossly?
My point yesterday was that even if "-" and "+" are notations that are used for relative pressure, that doesn't have anything to do with whether the word "polarity" is used with respect to sound waves.
Polarity without plus or minus is a weird concept.
To refresh your memory about yesterday, I wrote:
You could agree that positives and negatives, inversions (usually used to refer to 1/x) or opposites (usually used to refer to -x) are all appropriate descriptive terms, and none of those choices would necessitate nor even suggest the use of the term "polarity". That is a word that means different things in different contexts, and it is clear that there is no consensus usage of the term as applied to sound waves.
. . . in other words exactly what I'm saying now—that a consensus to talk about pluses and minuses doesn't mean a consensus to use the term "polarity", despite the logic in doing so. Bongomatic 10:00, 5 December 2009 (UTC)
Sorry mate, I don't usually bother reading your scribblings all the way through, too little time , too many idiots etc. Um, do you get paid by the word? Phase is the wrong word. Your references to phase are wrong. Greglocock (talk) 10:55, 5 December 2009 (UTC)
So are you saying that invert is acceptable? I don't understand your objection to that, as you know words have more than one meaning, using inverse to mean the reciprocal of a number is one example, since, by and large, people do not divide 1 by a coffee cup when they turn the cup upside down. I am happy with any reasonably accurate synonym that works in the time domain. Incidentally http://dictionary.reference.com/browse/polarity . Phase is the wrong word. Your references to phase are wrong.Greglocock (talk) 21:38, 5 December 2009 (UTC)

Fascinating though this squabble is, it doesn't have much to do with the article itself. The current wording suggests the electronics invert the audio signal directly, which is definitely wrong; it's the electrical signal that gets inverted and that inverted signal generates the "anti-noise." I've updated accordingly. Madgenberyl (talk) 18:23, 12 May 2011 (UTC)

External link to a members only site[edit]

The external link to the NYT review is "members only". This should be replaced by a link to a site that is freely accessible. 99.11.160.111 (talk) 07:33, 14 June 2010 (UTC)


COME ON NOW, DEFINE AMC — Preceding unsigned comment added by 8.225.200.133 (talk) 22:36, 15 August 2013 (UTC)

Secondary sources please![edit]

In my edit today I paraphrased someone else's contribution, after reading online abstracts of the papers cited. The papers do support the article content, but are small studies so I wonder whether they are really reliable. If you have more knowledge of this field, can you please suggest any secondary sources? Such references would be preferable according to the WP:WPNOTRS policy and if there's wider evidence, then secondary sources would reflect that.--Egmonster (talk) 03:39, 10 September 2013 (UTC)


Queasy FUD[edit]

In my opinion one reference by a health blog doesn't really count as enough of a reason to put in this rather odd claim. I'll leave it in for the time being but may zap it if I ever pay attention to this article again.Greglocock (talk) 05:51, 6 January 2014 (UTC)

I don't feel qualified to "zap" anything, but I note that the link for the queasiness claim goes to a headphone review site. This type of site often features reviews paid for by the companies recommended; in other words, this is spam. The site mentions but does not substantiate or cite a source for the claim. A cursory search shows enough mentions of this phenomenon to indicate it really is a thing for some people. Here's a potential better link, though not an ideal one: http://www.nytimes.com/2011/01/20/technology/personaltech/20askk.html?adxnnl=1&adxnnlx=1390593879-TVv/GobMdvaPqn+VUVV9yQ 63.142.214.71 (talk) 20:13, 24 January 2014 (UTC)
Whatever source you find will have to meet the requirements of WP:MEDRS since we are talking about a potential health hazard. The very stiff requirements of MEDRS serve as a major stumbling block for those who would have Wikipedia describe speculative hazards or personal stories about hazards. Binksternet (talk) 16:49, 19 January 2015 (UTC)
That NYT article still sounds more like anecdote than actual evidence. Greglocock (talk) 21:16, 19 January 2015 (UTC)

Requested move 20 June 2017[edit]

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: withdrawn by nominator. Triptothecottage (talk) 01:18, 24 June 2017 (UTC)



Noise-cancelling headphonesNoise-canceling headphones – This has been discussed before on this talk page, but never adequately resolved. Although the distinction between "canceling" and "cancelling" happens to fall under WP:TITLEVAR, it seems this article should be moved to comply with the consistency demanded by WP:CRITERIA to match noise canceling and noise-canceling microphone. Google Trends and Google Ngrams are ambivalent. Triptothecottage (talk) 02:54, 20 June 2017 (UTC)

  • Oppose Indian English has two "ll"s, that makes it automatically the more common spelling. In ictu oculi (talk) 11:26, 20 June 2017 (UTC)
  • Oppose per TITLEVAR – this article is consistently spelled in British English (cancelling, analogue), even including external links. WP:CONSISTENCY is the weakest of our five criteria and I don't think it beats ENGVAR/TITLEVAR, at least not in this case; moving this would open a can of worms. No such user (talk) 13:50, 20 June 2017 (UTC)
  • Oppose. This article has contained the two-ell spelling since the beginning. I see no compelling need to change from UK English to American English spelling. Both are allowed, which throws the idea of consistency for a loop. Binksternet (talk) 12:54, 23 June 2017 (UTC)

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.