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Noise-canceling headphones without the headphone

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Re: Noise-canceling headphones without the headphone

#91

Post by eCa »

ekanes wrote: post #37
duxup wrote: post #19

Earlier quoted context omitted.

Since my son has been remote learning at a desk next to mine I've been wearing noise cancelling headphones a great deal. The skin around ears have been super sensitive due to what I assume is just the natural heat build up from wearing headphones and pressure on skin not used to having pressure on it all the time. The skin is raw and irritated. It's not terrible, but not comfortable for sure and has been limiting how…

If you are able to afford it, I've found the more expensive noise canceling headphones to be dramatically better, softer and more comfortable for long wearing. I'm def not an audiophile, so I'm more talking comfort than anything else... The one I've been really impressed with is the Bose Quietcomfort 35 II. They're usually $300 but often on sale on Amazon for $200.

+1 on those. I’ve probably been wearing mine for 14 hours per day since March with, AFAICT, no adverse effects.

Re: Noise-canceling headphones without the headphone

#92

Post by ohazi »

74d-fe6-2c6 wrote: post #90
marcan_42 wrote: post #78

Edit: they cheated, this isn't ANC and will never work as ANC. See below. This sounds pretty fundamentally different from normal ANC. A common misconception is that ANC headphones "predict" the incoming noise and cancel it (and thus "they're good with constant noise but not sudden changes"). In reality they're just hybrid open-loop/closed-loop feedback systems. Specifically, the mic inside the cavity works with the s…

> This works for wavelengths smaller than the cavity size (A) "This" works for a wavelength > and above a certain frequency all you have is passive muffling (B) "This" does not work for a frequency > F. (B') "This" works for a frequency --- Don't A and B' (or B) contradict each other? Because an upper limit for the wavelength equates to a lower limit for the frequency - not an upper limit. What is your background tha…

It's clearly a typo. Should be "This works for wavelengths larger than the cavity size."

A long wavelength implies that the phase of the reference input and feedback input are similar, which is what allows you to just subtract them.

Your processing delay, the distance between the speaker and the microphone, and the speed of sound are all fixed, so as the wavelength gets shorter, the relative phase difference between the two signals you're trying to subtract increases. At a certain point, you run out of phase margin and can no longer just subtract them anymore.

If you were designing an ANR system, you'd probably want to put a low pass filter somewhere around this point to prevent your feedback system from oscillating.

Re: Noise-canceling headphones without the headphone

#93

Post by marcan_42 »

74d-fe6-2c6 wrote: post #90
marcan_42 wrote: post #78

Edit: they cheated, this isn't ANC and will never work as ANC. See below. This sounds pretty fundamentally different from normal ANC. A common misconception is that ANC headphones "predict" the incoming noise and cancel it (and thus "they're good with constant noise but not sudden changes"). In reality they're just hybrid open-loop/closed-loop feedback systems. Specifically, the mic inside the cavity works with the s…

> This works for wavelengths smaller than the cavity size (A) "This" works for a wavelength > and above a certain frequency all you have is passive muffling (B) "This" does not work for a frequency > F. (B') "This" works for a frequency --- Don't A and B' (or B) contradict each other? Because an upper limit for the wavelength equates to a lower limit for the frequency - not an upper limit. What is your background tha…

Sorry, that was an edit typo. I originally had "frequency" but I figured that would be confusing when juxtaposed to "cavity size", took the inverse and forgot to flip the sign.

My background is audio processing is one of my hobbies, I have torn down and repaired noise canceling headphones and understand how they work (and have previously talked about this on Reddit and been corroborated by an actual engineer at a company designing such headphones), I have implemented laser galvanometer closed loop feedback systems and worked with them (which is both a similar control system problem, and a different part of OP's research paper on the light path), I have attempted room and speaker response cancelation (and wrote my own DSP firmware for implementing biquad filters, which I use for my DIY living room rig), making an open source speaker calibration system is in my future project list and I've recently done a lot of thinking about this... and, most importantly, since this is neither my professional nor academic field I have no reason to overstate my claims or mislead about the importance of my work, unlike way too many academic researchers (see also: that guy who I recently called out for being a paper mill about side channel leakage methods after he successfully spun a false media story about generating Wi-Fi signals from RAM using a misleading paper title; in that case infosec is in fact one of my professional fields).

I don't like to brag or anything, I'm just a curious guy who likes tinkering with (lots of) things... but if you insist on asking "what are your credentials", well, there you go.

Re: Noise-canceling headphones without the headphone

#94

Post by 74d-fe6-2c6 »

ohazi wrote: post #92
74d-fe6-2c6 wrote: post #90

Earlier quoted context omitted.

> This works for wavelengths smaller than the cavity size (A) "This" works for a wavelength > and above a certain frequency all you have is passive muffling (B) "This" does not work for a frequency > F. (B') "This" works for a frequency --- Don't A and B' (or B) contradict each other? Because an upper limit for the wavelength equates to a lower limit for the frequency - not an upper limit. What is your background tha…

It's clearly a typo. Should be "This works for wavelengths larger than the cavity size." A long wavelength implies that the phase of the reference input and feedback input are similar, which is what allows you to just subtract them. Your processing delay, the distance between the speaker and the microphone, and the speed of sound are all fixed, so as the wavelength gets shorter, the relative phase difference between…

Maybe that's why the speakers of Sony's xm series are designed to lie flat on (my) ears while Bose's leave more space but are considered slightly less efficient at noise cancelling compared to the xm's. For me ANC is by far the most important feature but having my ears pressed for longer than one hour is painful. And I tend to wear my Boses (QC35 and HP700) easily 8+ hours.

Re: Noise-canceling headphones without the headphone

#95

Post by 74d-fe6-2c6 »

marcan_42 wrote: post #93
74d-fe6-2c6 wrote: post #90

Earlier quoted context omitted.

> This works for wavelengths smaller than the cavity size (A) "This" works for a wavelength > and above a certain frequency all you have is passive muffling (B) "This" does not work for a frequency > F. (B') "This" works for a frequency --- Don't A and B' (or B) contradict each other? Because an upper limit for the wavelength equates to a lower limit for the frequency - not an upper limit. What is your background tha…

Sorry, that was an edit typo. I originally had "frequency" but I figured that would be confusing when juxtaposed to "cavity size", took the inverse and forgot to flip the sign. My background is audio processing is one of my hobbies, I have torn down and repaired noise canceling headphones and understand how they work (and have previously talked about this on Reddit and been corroborated by an actual engineer at a com…

So, in your opinion there's no hope for active voice cancelling? Maybe with earbuds?

I'm a silence junkie living in world getting noisier with every day it seems - so this subject is of high personal importance to me. That's why I'm interested in getting an idea about where to place your assessment.

Re: Noise-canceling headphones without the headphone

#96

Post by marcan_42 »

74d-fe6-2c6 wrote: post #95
marcan_42 wrote: post #93

Earlier quoted context omitted.

Sorry, that was an edit typo. I originally had "frequency" but I figured that would be confusing when juxtaposed to "cavity size", took the inverse and forgot to flip the sign. My background is audio processing is one of my hobbies, I have torn down and repaired noise canceling headphones and understand how they work (and have previously talked about this on Reddit and been corroborated by an actual engineer at a com…

So, in your opinion there's no hope for active voice cancelling? Maybe with earbuds? I'm a silence junkie living in world getting noisier with every day it seems - so this subject is of high personal importance to me. That's why I'm interested in getting an idea about where to place your assessment.

Active noise canceling earbuds already exist, and probably perform about as well as one can hope modulo small incremental improvements. I mean, the AirPods Pro are already damn impressive here. You could probably do better by cramming more and more technology closer to the actual ear /at the tip of the earbuds, perhaps? These things do cancel the low-mid end of voice frequencies quite well. I imagine with enough miniaturization you could increase the range.

But room-scale or free-space noise cancellation only works when either 1) your noise source is extremely predictable, or 2) your noise source is low-dimensional. It's just never going to work for the general case unless you can somehow sense the entire soundfield. The entire sum of what waves are traveling in which directions. Not just a few microphone inputs. It's going from 1D data to 3D data, the difference between a light sensor and a CAT scanner. And it needs to work at 20kHz response.

I guess hypothetically you could do something like wrap a room in microphones and compute the sound coming in in all directions, then with a very good adaptive model be able to cancel noise from outside within it. But if you're going to draw a boundary and wrap it in a massive array of microphones... Aren't you better off just adding insulation material? :-)

Edit: just as a baseline, I very crudely tested my Bose QC20 earbuds (which aren't exactly bleeding edge tech) and I think they get about 10dB active cancellation at 1kHz, which goes down to nothing at 2kHz. Human voice fundamental frequencies are typically 85-180 Hz for adult cis men and 165 - 255 Hz for adult cis women, so this level of ANC does get rid of the fundamental and a few harmonics. I might test a friend's AirPods Pro later and see if they're better. 1kHz has a wavelength of ~34cm, so I think there is room for improvement here in the earbuds case. I'm not experienced enough in this field to have a good feel for the numbers beyond order of magnitude estimates, but I think going up to 4kHz might be doable, given that for earbuds we're talking about cavities in the ~5cm range. Might need more mics/drivers and more miniaturization to pull it off, not sure.

For those wondering, the test methodology was to play a tone, turn on cancellation (which has a delay), then turn off cancellation (which is instant) simultaneously with decreasing the amplitude of the tone, and trying to match the perceived loudness between both cases.

Re: Noise-canceling headphones without the headphone

#97

Post by 74d-fe6-2c6 »

JBiserkov wrote: post #3

>wearing active noise canceling headphones for extended periods of time can be uncomfortable and even cause injury Does anyone know what type(s) of injury is this referring to, how long is too long and how widespread/likely it is?

This is somewhat the pink elephant in the room when it comes to ANC. Last year lots of people complained about a simultaneaous reduction of ANC across several brands and models brought with firmware updates. One suspicion was that Bose, Sony, Apple have some info about possible damage from ANC and did this to avoid liability. I'm wearing ANC headphones up to 12 hours a day now for 5 years. I didn't experience any damage as far as I can tell but I am worried about it. There are several possible ways how wearing ANC headphones that long might cause damage. The build up of relative humidity might for example promote infections. But the big question is if the ANC itself might cause damage. As far as I know there are no conclusive studies on that.

Re: Noise-canceling headphones without the headphone

#98

Post by 74d-fe6-2c6 »

marcan_42 wrote: post #96
74d-fe6-2c6 wrote: post #95

Earlier quoted context omitted.

So, in your opinion there's no hope for active voice cancelling? Maybe with earbuds? I'm a silence junkie living in world getting noisier with every day it seems - so this subject is of high personal importance to me. That's why I'm interested in getting an idea about where to place your assessment.

Active noise canceling earbuds already exist, and probably perform about as well as one can hope modulo small incremental improvements. I mean, the AirPods Pro are already damn impressive here. You could probably do better by cramming more and more technology closer to the actual ear /at the tip of the earbuds, perhaps? These things do cancel the low-mid end of voice frequencies quite well. I imagine with enough mini…

I'm more of a lazy pragmatist than a passionate hacker. So, I guess I should invest my energy, time and money into just finding a less noisy place to live. I'm not suffering from misophony - I just hate hearing my neighbours or loud vehicles with a vengeance :D

Re: Noise-canceling headphones without the headphone

#99

Post by dusted »

Gosh, if this makes it into airplanes and such I hope there will be a way to turn it off, I've not yet encountered an ANC headset that does not make me dizzy. Sure some sounds are reduced, but they give this strange "pressure" in my head, hard to explain, like being several meters under the water.

Re: Noise-canceling headphones without the headphone

#100

Post by slavak »

chii wrote: post #31
PurpleFoxy wrote: post #26

Earlier quoted context omitted.

I don’t think this is even possible. Noise canceling works by creating reverse waves that hit your ears at the same time. You have to be able to calculate how long it will take for those waves to hit each set of ears and be able to direct sound at them.

That's the simple, signal-processing oriented way to noise cancellation. But what if the software/ai is advanced enough to reproduce a sound, but erase a certain aspect of it? Like how photo editing can edit out an object or background? Then the headphones can use a seal to completely block out all noise, and play only the sounds the user selects!

This already exists: https://www.geekwrapped.com/guides/best-electronic-ear-muffs

The utility is limited by the limitations of passive noise attenuation devices. These things are great for the shooting range, because bringing gunfire down to a level that won't damage your hearing is pretty easy. There's no kind of earphones that can just completely block out all sound, though.

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