Talk:Noise-cancelling headphone

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[edit] Do They Cause Damage

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)
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)

[edit] Insulating Headphones

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)

[edit] Audible Counter-Noise?

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.
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)

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

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)

[edit] Speed-of-sound considerations

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 (talk • contribs) .

[edit] Teachers

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)

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

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)

[edit] Spelling

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 English — jammycakes 10:43, 21 November 2006 (UTC)

[edit] "poorly adjusted"

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)

[edit] List of models of noise-cancelling headphones

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)

[edit] Passive vs active noise cancelling

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)

[edit] Bulkiness and other disadvantages

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 [citation needed] 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)
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