Noise-canceling headphones without the headphone | Hacker News Reader

Noise-canceling headphones without the headphone

spectrum.ieee.org

203 pointsystad117 comments

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 speaker as a closed loop system to equalize the pressure inside in real time. This works for wavelengths smaller than the cavity size, give or take. So there is no prediction, and they don't care whether the noise is constant or not. They just have a given frequency response, and above a certain frequency all you have is passive muffling (no active cancellation).

But this can't do that, because the speakers are much further away from the user. So it had to predict to get any kind of decent frequency response. I wonder how they're doing that. A lot of noise sources are uncorrelated and not predictable...

Edit: They cheated. They're taking direct feeds from the source loudspeakers, and then all they have to do is track the transfer function to cancel that out from another speaker. This will never work in the real world, where sound sources are not coincident with your microphones (or lack thereof as in this case). Cool research, zero real world application as a true ANC system.

I have no idea why they're selling this as ANC. This looks more like a system for computing real time room/response calibration as the user moves around their head. That's valuable, in a completely different use case.

The actual study is here [0] and the abstract and introduction do a much better job of describing what the study is actually about.

I encourage you to read at least those before you dismiss the research and its real-world applications.

TL;DR: The purpose of the research is to try out a new way of figuring out which sound is going into the user's ears, so that it can be cancelled out. Current methods work for lower frequencies but not for higher frequencies.

They "cheated" because they're testing one component of the system and the "cheating" component is immaterial to the research they're doing.

[0]: https://www.nature.com/articles/s41598-020-77614-w

They "cheated" because they did the easy part, and the "other component" has no known solution.

What they're handwaving away is the real problem. The reason why current methods work for lower frequencies and not for higher frequencies is that your microphone, emitter, and ear all need to be enclosed within a volume << the minimum wavelength you can handle, to eliminate sound field and propagation time effects and let you treat the noise cancellation problem as a point problem in space.

Once you put the ears in open air and the emitters away from them, the problem isn't figuring out the sound that's going into the users' ears, it's figuring it out in advance. The ANC speakers have to send the complement signal before the original signal arrives at the ears, so they both arrive coincidentally.

In other words, the "missing part" to make this research work is time travel (if you use their sensing technology as the only input). Or maybe full-volume sound field sampling and characterization technology (if you don't). Neither of which exist, and which are orders of magnitude more difficult than this research.

The handwave part is "The constraint of the possible locations [of microphones] would affect the control performance and this remains a topic to be further studied in the ANC community."

Yes, it would completely destroy high frequency performance, which is what they were trying to achieve, in anything but lab scenarios (such as the sound sources still being loudspeakers and the microphones being directly in line between them and the user). Real world noise doesn't come from loudspeakers, it comes from all around you. Good luck using distant microphones to compute the expected sound at a user's ear in advance, with any kind of accuracy in the high frequencies.

At best I imagine they could achieve adaptive cancellation for a set of slowly moving pointlike sources in an otherwise simple room, with a number of microphones greater than the number of sources. It's like RF MIMO systems. But again, this is orders of magnitude more work to implement, and real world constraints are going to kill your high frequency response. And for larger sources - forget it. You just can't characterize the transform for that. Not enough dimensions in your input data to solve for it. So anything mechanical, stuff where the noise isn't coming from a literal speaker with a 1-dimensional input signal - nope. As the uncertainty and source size grows, your high frequency response goes down the drain.

No, the missing part is not time travel. Sound comes from the skin and engines of the plane, where microphones could be located, and could potentially predict sound throughout the plane well in advance with an appropriate microphone array. You'd need a fair number of microphones, but I suspect the noise profile isn't too chaotic, which helps. You're talking about things like jet engines (which are repetitive), turbulence (which seems chaotic, but in practice, you shed vertices at a known rate), and a known cabin configuration (modulo people moving about). I suspect while the general solutions suffers from the curse of dimensionality, the specific one probably doesn't. A reasonable number of microphones, combined with decent models, could characterize the whole sound field.

Speakers, located in the seats, if they knew where ears were, could play sound to cancel that.

Decent microphones are $2, and what was expensive were things like microphone preamps, ADC, and the whole data pipeline. From there, we need a shit-ton of computation which really wasn't practical until... big-ass computation systems came out for the rise of ML.

The problem is hard today, but definitely not impossible. I don't think I would have given that same answer a decade ago. An NVidia Titan V brings over 100 teraflops. That's a lot of cycles one can throw at trying to predict sound by my ear from sound at the skin of the airplane in real-time.

If you've ever been in an airplane, you'll know that airplane cabin noise is largely uncorrelated rumble, not fixed-pitch components from the jet engines and such. Good luck solving for the response at a user's position for that, no matter how many microphones you throw at the problem.

https://www.youtube.com/watch?v=te3pyLk_wBs

Spectrogram sample: https://mrcn.st/t/flight_noise.png

I get that this is HN, but no, ML and AI do not magically solve all problems.

Thankfully, most of the energy is in the low frequencies, which existing noise cancellation systems can already do a god job of dealing with in the near field.

Research is an incremental process and even if their proposal has no practical application right at this very second, it's still a new idea that hadn't been tried before they did it.

Instead of focusing on the fact that these researchers didn't singlehandly revolutionise ANC in a single study, how about we focus on what they did do?

That's why I'm confused as to why they're selling this as being relevant for ANC (optimizing for the news cycle?), when it would be a lot more useful to talk about things like optimizing free space speaker systems for a user's position, say, for VR.

Like, the idea of remotely sensing where a user's ears are and what they're picking up is useful. Just not for far field ANC.

> This works for wavelengths smaller than the cavity size

(A) "This" works for a wavelength < L.

> 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 < F.

---

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 that justifies your very confident demeanour?

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.

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.

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.

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.

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

See, this is why when I shop for apartments to rent, concrete walls are a requirement. Not just so I don't hear my neighbors, but also so they don't hear me, since I make music ;)

At my current place I've pretty much concluded that anything but deep bass just doesn't transfer. Even at 5 in the morning, I can listen to stuff at a reasonable listening volume without disturbing my neighbor, as long as I'm not pumping out bass below 80Hz or so. And the neighbor recently got a dog and I haven't heard her bark even once when she's home :)

> 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? :-)

Well, let's do the math here. I can't find the data sheet for the weight of an electret microphone cartridge, but let's assume 4 grams. A thousand microphones -- assuming we want 100 the length of the airplane and 10 around -- is around 4 kilos. Add another 2 kilos for computation, and a few more for wiring, and you've added the weight of a piece of luggage.

Now, let's say you want to add 2 inches of mineral wool sound insulation. I'm assuming 100 meters x 10 meter circumference (I have no idea, but the numbers scale the same). You've added (quite literally) half a metric ton to your airplane. And made it 2" thicker, either reducing cabin space or increasing drag.

Plus, sound insulation does very little for low frequencies, which is the majority of airplane noise.

Assuming you want to cancel frequencies up to 1kHz, you're going to need mics every 30cm at least for a useful sound field. For a 787 fuselage, that's about 60 around by 190, let's round that down to 10000 microphones. But of course, then you need electronics for them, and a way to carry the signals back to somewhere for processing. That's about 10 Gbps of data, fine, doable, but then you need to process it. Since you need to cancel separately per passenger, that's 2.4 million filters (10k mics * 242 passengers) to process. Nevermind that since this is a plane, there is a huge amount of overhead due to safety requirements.

This is all assuming this whole idea works, which it probably won't, because it's not just about the microphones on the fuselage but also how sound is transmitted inside the plane and other noise sources.

That sounds reasonable. Let's do the math your way in both directions:

1) Assuming system-level model

10,000 microphones * 8 kilosamples per second = 800 megasamples per second.

NVidia Tesla does 100 teraflops. I get about 125,000 FLOPS per sample. That feels adequate to me!

2) One filter per microphone per passenger. We need to divide by 250.

500 FLOPS per sample per passenger. That's more than enough for a very fancy IIR.

Of the two, I think #1 is more likely to work than #2, precisely because you want a coherent model. If you want to adjust your model for someone walking down the aisle (or any kind of system ID), that's a lot easier with 125,000 FLOPS per sample than 500 FLOPS per sample.

Right, and now you've achieved the same noise cancelling performance... That off the shelf noise canceling headphones achieve (1 kHz) without putting 10000 microphones on the plane.

Again assuming this all works, which is a massive if.

Look, this isn't practical.

.... in the same way that having a billion transistors in a computer isn't practical. Or a computer in every car tweaking fuel injection. It's not practical until it is. Electronics goes down in price. Algorithms improve. Insulation stays fixed or goes up in price. I would say it's not a question of "if" but "when."

The answer to that might be right now (we couldn't do it before, and we probably can today) or it might be in a decade. But electronics will keep falling in price. 10,000 microphones * $5 per microphone+electronics = $50k.

The advantages of cancelling an entire wavefront go well beyond passenger comfort too. Industrial noise cancelling systems are more about equipment life than about employee comfort. I had laptop screws unscrew on airplanes before, due to vibration. If planes need less maintenance as a result of active vibration reduction throughout the airplane, you'll make up that $50k virtually overnight.

As a footnote, the crazy part here isn't the 10,000 microphones, but the speaker-at-every-seat part. You'd almost certainly want both the microphones and speakers in the skin of the airplane. But that's a story for another day.

This comment is technically incorrect.

Noise-cancelling headphones work the way OP described, and are limited to working in a cavity which is smaller than the wavelength.

There are predictive noise cancelling systems too. These are commonly built into industrial equipment. You might, for example, have a fan or motor which spins at 5000 RPMs, and what do you know, it has a consistent noise profile on each of those rounds. If you cancel that noise profile, you do pretty well. These systems both reduce noise and extend equipment life by reducing vibration. They also work to higher frequencies (in part because speed-of-sound in metals is > 10x that in air, and what matters is wavelength more than frequency).

There are ones which are open-loop used in HVAC systems. If I have a pipe, I can record sound on one end, and play a cancelling waveform on the other end, with an appropriate delay. I haven't followed the field, and when I looked, these were mostly expensive prototype systems (I'm not sure if they ever made it into mainstream use), but they did work. They needed to be calibrated for each HVAC, which made them impractical for most real-world applications.

There are all sorts of ways to do active noise cancellation. Many of these could be implemented on airplanes. Most of these techniques were implemented decades ago, when computation was a lot more expensive. A simple feedback loop is a few opamps, capacitors, and inductors, so pretty cheap to toss into headphones with 1990's-era technology. One could do a lot more with teraflops....

Yes, as I said, this doesn't work in the general case when your noise source is uncorrelated and not predictable. If you have a predictable noise source then you've solved the time travel problem and you can cancel it any way you want as long as you can obtain feedback from the location of the user's ears.

We're talking headrest ANC here (for use cases like consumer ANC headphones), not built-in noise reduction for industrial systems.

An airplane is an industrial system....

And in either case, the design of algorithms depends on much more on context than on whether it's "consumer" or "industrial." In this case, the context looks a lot more like industrial machinery.

Some cars such as new Genesis models attempt this.

Always great to see development in this domain. IWAENC and Silentium come to mind as the forefront. I hope one day the researchers will realize that they are trying to cancel the wrong source. Instead of cancelling noise external to the human, the real breakthrough will be to cancel the human voice. This will confer privacy and other benefits in areas of increased population density. I would prefer a smartphone to have a feature like that than an incrementally snazzy camera, for example.

> I hope one day the researchers will realize that they are trying to cancel the wrong source

I dont think its due to intentionality just that low pitch is easier to cancel than high pitch things like voices.

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!

If we could make a seal that blocks out all noise small (and confortable) enough to fit around a headset, we wouldn't need the whole NC setup.

Earplugs below my bose headset work wonder to block out anything short of cataclysmic, but it's hardly practical. And I can't exactly play music with those on...

Your ears do breathe. So that’s problematic for long term hermetic ear seals.

It's funny because the best passive noise canceling IEMs are basically ear plugs with drivers in them. Blocks background noise as well as ANC but only weigh a few grams.

I think you have misunderstood the parent comment. The suggestion isn’t to create configurable anc headphones but instead to create a device that is able to cancel out the sound of your voice from the ears of other people around you so you can speak in public privately.

The problem is you can’t possibly work out exactly how and when the sound will hit each set of ears around you to be able to direct a beam of sound to their ears (assuming it’s even possible to have such directional sound)

The problem is significantly easier with headphones. You have a headphone and speaker in between your ears and the sound. The distance between the microphone and your ears is constant so you can perfectly time the negative sounds.

I never said it would be easy, but you make a good point. Compensating based on other sets of ears would be tough, because their locations are unknown and change fast.

Directional sound is possible to an extent, Woody Norris gave a TED talk about it a long while back, it is called hypersonic sound. I think it uses ultrasound to generate compressions and rarefactions far away. I realize it sounds like science fiction, but you could perhaps transduce sound to electricity and again to sound, sending the signal of your voice away from you faster than the speed of sound, in time for a cancellation wave to be generated and have an effect. I suppose the analogy would be quiescing a ripple in a pond.

There was a product announced a few years back called Hushme that proposed to accomplish this goal. It attempted to create an acoustic seal around the wearer's mouth, and somewhat predictably, it looked ridiculous: https://www.news.com.au/technology/gadgets/wearables/this-ca...

Neat, but weird. Muzzleme is more like it.

The implications for a dystopian society abound! Minority Report billboards or 1984 actual silencing of unwanted voices...

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.

Right, but the speed of sounds is slow. So things like placing a microphone 6 feet closer to the source allows for much more effective noise cancellation. Current tech in earphones skips that by using past noise as a prediction of future noise, and as a result only works on near constant noise of airplanes and other near constant sources of noise.

> only works on near constant noise of airplanes and other near constant sources of noise.

That is simply not true - at least in my experience with an old model of Sony headphones. It's possible that prediction plays some role, but I bought mine with specific purpose of silencing neighbor's kids.

They work really well with this kind of sporadic, random noise and the difference between turning on active cancellation and just passive attenuation due to ear muffs is very noticeable. I'm talking about low-frequency noises that are mostly transmitted through the vibrations in the walls and floors - feet hitting the floor while running, ball bouncing of the walls and so on.

>I hope one day the researchers will realize that they are trying to cancel the wrong source. Instead of cancelling noise external to the human, the real breakthrough will be to cancel the human voice.

Only few care for the latter and millions/billions care for cancellation of external sources.

Besides, "cancelling the human voice" would just provide a false sense of security, as said voice would still need to be received by others -- and like any message it could be intercepted.

That is what encryption is for. You only need to secure the voice until it can be encrypted.

Worth noting that the feeling of privacy is a lot about perception. People feel better if they know those they see around them cannot hear their private convo. That is why they speak softly and put their hands to their mouth talking in public places (the other part was to boost the signal, before the advent of differential microphones).

Don't get me wrong, I most definitely agree external cancellation is terrific, be it active or passive. In the passive realm people use traditional dampening materials, as well as MPPs (micro-perforated plates) in certain industrial applications.

> the real breakthrough will be to cancel the human voice

If you want to cancel another human, just build a wall.

>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?

I suspect the article is referring to things like bruising from tight fitting earcups or maybe muscle strain from the weight of the headset, not something specifically related to the noise canceling function (except perhaps from excess noise caused by ANC circuit malfunction that might cause a temporary threshold shift)

Aftermarket options can be purchased to mitigate discomfort from ear protection equipment.

The Sightlines Gel Ear Pads from NoiseFighters is a popular option for earcup replacement.

The IceVents Classic Ventilated Headband from Qore Performance is a popular option for headband replacement.

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 much I can wear any over the ear or even on the ear headphones.

Huh, as another commenter said, some people are just more susceptible than others but I've worn headphones for many hours a day to no ill effect. There should be no clamping pressure on the ears, the weight should be on the headband. Might be worth looking at different options. Over-ear vs On-ear can make a difference.

Might try different pairs. My cans for recording are HD180s, pretty standard and they really squeese your head.

My bose quiet comfort are comfortable for maybe an hour or two before i even notice I am wearing them.

From there small in ear with noise cancelling can be good

If your ears stick out or are bigger you should really go to a best buy or music shop or whatever and try on cans until you find ones that fit

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.

Yeah, I sold my sennheiser HD6XX for a pair of Bose QCs. It’s just so much more comfortable.

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

I practice a grappling martial art. If you bruise the tissue in your ear too much small pockets of fluid can form between your ear and the cartilage. If this fluid is not drained and the ear kept compressed it can harden forming cauliflower ear, deforming the ear. Some people are more susceptible to it than others. I imagine that would be a worst case injury. I don’t know of this happening with headphones, but it seems plausible.

I don't understand either. In fact, active noise cancelling pilot headsets are usually more comfortable and less tight fitting. This is because by being noise cancelling, these can get away with lighter passive noise isolation.

The only kind of injury I can think of is related to being less aware of your surroundings.

Recently I started a job that has me using a headset with ANC (active noise cancellation). It was OK for the first week or two but then I noticed my head hurt. My ears felt full and I had ringing in my ears that was quite loud. I have mild (self-diagnosed) tinnitus but this was beyond that by a significant amount.

I'm aware of how noise cancelling technology works it's by creating an opposing sound wave of equivalent energy to nullify the unwanted sound wave.

My theory is when I am off a call and I have the headset on my head with ANC enabled it's working to cancel the background noise. It's only needed on a call but it's obviously on all the time. These are not cheap headphones I've seen them for $300 so not cheap but I'm sure not the highest end.

I've tried taking them off, put around my neck, on my head between calls. But a few times I've fumbled them and hung up on someone or picked up before I was ready. My solution was to turn off ANC which made the sound clearer and my ears don't ring as bad as with ANC on.

My own anecdotal evidence but there is an obvious effect on my ears. I was about to go to the doctor the ringing was getting so bad.

Try IEM's.

IEM = In-Ear-Monitors?

Yup.

Try getting an employer to fork out for IEMs when $300 headphones “do the job”.

You can get a decent set for about a hundred bucks.

Shure SE215 is less than a hundred!

That said, like with most IEMs, sleeves should be replaced sometimes (probably once a month or if you get any dirt on them—be careful with handling and don’t let that stuff get into your ear canal), so that should be factored in the price.

Which sleeves you choose makes a big difference—they are more or less the noise isolation part of IEMs, and they make or break your comfort when wearing. I swear by the combination of SE215 + Shure’s original black foam sleeves (or, if those cannot be obtained, Westone’s foam eartips). Passive noise isolation in this setup is better than ANC in AirPods Pro for me subjectively (although according to rtings.com’s measurements they go head to head), and is easy to wear for long periods of time.

(I guess I’m replying to thepostoffice but for the most part this is addressed to dghughes’s upstream post.)

WARNING:

IEM seal the ear canal causing a build up of moisture and ear wax that can lead to infection in some people.

Huh, they don’t have an “off” more for noise cancellation? I read a review of the airpods max and they have three settings: on, transparency, off. The last one has to be enabled in settings.

I am assuming this is a fairly common feature for headphones? If so you might be able to switch models to one that has an off mode, if yours don’t.

I've been looking on and off for a pair of ANC earmuffs for factory work, but reports that some people experience headaches combined with the pretty high price have caused me to keep putting off the purchase.

I'd love to learn more about this too!

I wear Sennheiser HD1 M2's (with ANC) for ~8h/day, 5d/week, and have been for over 2 years -- with no discomfort or unwanted side- or after-effects. Ofc I'm careful about volume level, and I take frequent breaks from both screen and headphones (albeit for the sake of my eyes). I'm a healthy 47yo software architect by trade, also a lifelong musician and music afficionado. I care about -- and for! -- my ears and hearing, and would be grateful for any good links to credible sources (ie peer-reviewed scientific studies) which highlight hidden dangers or damage.

Likewise, some sources for audio damage from noise canceling would be great. I wear headphones 8+ hours a day for work. Around two months ago I upgraded my 10-year-old (cheap, wired) Sennheisers to some mid-range wireless ones with noise canceling, they're a bit heavier but otherwise just as comfortable and noise canceling is awesome for helping me focus. I've never had any negative effects from either (although I'm careful to keep the volume down).

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.

> Last year lots of people complained about a simultaneaous reduction of ANC across several brands and models brought with firmware updates.

Was this ever verified quantitatively? It sounds like the kind of thing that could easily be generated by group confirmation bias.

I read a theory suggesting that eardrum fatigue is the reason. ANC does not hurt us even if it is loud. We are hearing a sound but not a ”real” one, but our eardrums still vibrate a lot. The thinking is that high level ANC is as fatigue inducing to eardrums as prolonged music listening. That’s why I nowadays recommend to friends to not use ANC on its own for too long daily.

My new Ram 2500 diesel has active noise canceling and is the quietest ICE vehicle I’ve ever been in. Probably quieter than electric vehicles at high speeds.

Not to people outside your truck though..

That claim was never made, and you don’t know enough about the poster’s needs and circumstances to criticize their vehicle choice in general.

It’s a little on the quiet side for a 3/4 ton truck on the outside. But obviously not going to beat a Tesla in that regard.

Common rail diesels are very quiet compared to older style diesel engines. Some are so quiet you wouldn't even know it was a diesel. And with DEF you won't even smell the classic diesel exhaust smell. The loud smelling ones are due to modifications and probably also from "deleting" the DEF (which is illegal).

It’s relatively quiet but still has that distinctive diesel sound. It’s the latest Cummins 6.7 and for something that puts out almost 400hp it’s pretty quiet. I’m fairly sensitive to noise so between that and the ANC I’m pretty happy.

A large majority of these trucks get a delete installed. Numerous folks roll coal. In states without emissions control it’s a giant cluster.

I really doubt it’a a large majority.

Is it quiet on the outside too?

For a 3/4 ton truck, yes. Compared to a small car, no.

I’m sure most of the noise will come from the size/type of the vehicle (air displacement and styling) and tires. Truck tires are not known for being particularly quiet. The larger the tread, the worse the noise...

Yeah they’re also very poor in terms of aerodynamics by necessity. A tonneau cover helps more than you might think!

Can you switch it off/on to hear the difference? Would be interested to know the difference perceived.

Are there any other cars that do this?

I wish because I’m curious. You have to buy some aftermarket hardware for that.

And yes. Mostly luxury cars ATM but it’s growing.

Acura RL was one of the first to have active nose cancellation, in 2005.

Apparently electric vehicles like Tesla are noisy on the highway, where external noises dominate; due to less sound-deadening material to save weight.

I’ve noticed that.

Can confirm, the Model3 is not a wonderful place to be at 80 MPH. Wind a tire noise is embarrassingly bad for a car that can be optioned out to $60k.

They are finally upgrading to double glazed windows on post-October models.

Noise is only a little bit better. It’s still embarrassing.

What what I've heard the ID3 actually has more sound-deadening than normal and the LEAF's mirrors were designed to cause less wind noise.

That's an absolutely feature. Road noise is a big fatigue on bikes and older loud cars.

I work in this area.

There's a huge runway in front of us for both products and technology.

'Acoustic Holography' has worked for some time, commercial implementations have been few and far between, mostly because what's in the market is already selling boatloads without it.

It'll come eventually, there are a few groups dedicated to it.

A successful anchor in that space will allow companies to go deeper into applications.

Acoustic room splitting, Silence on demand, etc.

Sounds very interesting! Could you direct the interested to your favorite review article or another starting point?

An implementation or variation on this theme is surely the future of in-room audio:

https://en.m.wikipedia.org/wiki/Wave_field_synthesis

The math says, if implemented correctly, WFS is better than sitting in the sweetspot of any speakers. Also, there's no sweet spot with this technology.

I wonder if it is possible to mount a noise-cancelling device directly on the source of noise, for example, on a circular saw? The frequency of sound waves from a particular tool is pretty predictable and I can imagine a device with a mic or a vibrometer and speakers that clips directly to a tool and suppresses most of noise from this particular source.

I've been using ANC headphones since I started woodworking in the garage and it works for me but not for my neighbours. Soundproofing the garage is difficult and not always possible (not when the door is open anyway), so I would pay top dollar for something like this.

theoretically, if the saw has constant RPM then just playing back inverted recording loudly would do it. You just need to match them in phase :)

Yes I've had a similar idea with a condo neighbor with loud bass, it must be possible to have some attachment you put on the wall to cancel it out. That would sell well

It's a soundfield problem. This only works for wavelengths that are larger than the size of the emitters and the distance between them. And even then it only works well if you can get the emission pattern of your cancelling speaker exactly the same as the source.

So, assuming you had a magical beamforming speaker array around your circular saw, you'd still only be able to cancel frequencies around under 1kHz, because there's no way to get the thing in phase above that.

This is why noise-canceling earphones have much better active cancellation at high frequencies than headphones, which rely more on passive isolation until lower frequencies. They're smaller.

I expected them to be put elsewhere in the plane. For instance, my office has a floor with exposed AC units, and "noise-cancelling"[1] machines next to them that remove most of the sound of the AC. I wonder if something similar could be done for planes.

[1] Not sure exactly what the name of this device is.

Is that noise canceling or is it masking?

That "sounds" interesting but why not have a partition or a less loud AC Unit?

Do you have a picture of what it looks like? AFAIK room-wide noise cancellation can't work because noise cancellation requires the exact position of the listener to be known, otherwise the sound will not be canceled out and might even be amplified. see this animation: https://en.wikipedia.org/wiki/File:Two_sources_interference...., if one of the wave sources is the AC and the other is the noise cancellation machine, only some areas will have no sound, but others will have even louder sound.

It’s apparently possible on planes, so it could work for offices too. https://www.flightglobal.com/quiet-revolution/31793.article

I thought this was already in planes, such as Dash 8 (Q400) -- noise cancellation, although for the general cabin, not the individual seat passenger:

https://www.flightglobal.com/quiet-revolution/31793.article

https://apps.dtic.mil/sti/pdfs/ADA446777.pdf (see plots at end)

"So they used a remote acoustic sensing system built around a laser Doppler vibrometer (LDV), which measures non-contact vibrations over a wide range. In their tests, they placed a tiny, jewelry-sized, retro-reflective membrane in the ear as a pick-up for the LDV." These sound curious: these are the devices that three letter agencies have used to suss out sound from glass, aren't they?

https://en.wikipedia.org/wiki/Laser_Doppler_vibrometer "Security – Laser Doppler vibrometers (LDVs) as non-contact vibration sensors have an ability of remote voice acquisition"

I use a pair of bone conduction headphones and have some cheap earplugs. Better than any ANC headphone/earbud I’ve ever had at cancelling noise. You also don’t get that negative ear pressure or buzzing and they can be quite comfortable. I can be in the middle of a construction site or on a plane and not hear a thing. The one drawback is the sound quality but I’m not exactly an audiophile and tbh the newer bone conduction headphones sound fine to me.

I remember, years ago, a video on TED of a guy presenting working technology for generating sound using collapsing waves from multiple sources, so you can have sound limited to desired volume or cancel noise, so you could have silence next to a busy highway, etc. He was boasting high interest from military. His page/name and the video went offline soon after.

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.

Is this a heat engine? Feels like it has to be obeying the laws of thermodynamics and something has to get hot managing the pressure wave density in air. I'm guessing the speaker magnets and coils heat up.

Play enough noise, and the system will explode into fire...

I think you get destructive interference in some places (the ears hopefully) and constructive interference in other places (hopefully not the ears). So you’re moving energy rather than destroying it

Audio is basically negligible in terms of power.

Those massive stacks of speakers at an arena rock show are (in total) perhaps 20kW. The lights use far more.

Earbuds can we well south of one watt.

I get 'vertigo' from ANC headphones. This sounds like my personal hell

To me, it seems pretty obvious this can't work. The cancelling signal from your seat will have to be cancelled by all the other seats and vice versa, creating a feedback loop.

Does anyone here already tried ANC on these new true wireless earbuds ? Does a better better isolation always imply to a better sound quality ?

AirPods Pro certainly has much better bass with ANC on, and I'd say overall sound quality too. It also sounds louder, although I'm not sure if that's just perceptual: higher sound levels are fine to me with ANC off, but are unbearably loud with it on. That's in both loud and quiet surroundings.

I've noticed this as well. When I have ANC on in like a grocery store with music playing at a comfortable volume, then turn it off, I can barely hear the music.

ANC headphones are great for low-frequency (bass) sounds. But with cheap headphones I find I can still hear speech. I think new housing uses mass loaded vinyl to prevent high frequency sounds from passing through walls - perhaps heavy, 1lb or 1kg headphones with ANC are the solution for experiencing real silence in e.g. a busy workspace? Does anyone have an idea if material weight or density is a big factor in sound insulation? Along with air-tight sealing.

In general, anything heavy related to headphones = bad.

You can get the equivalent of state of the art ANC performance with a pair of passive IEM's that fit properly.

Try using memory foam tips if you have trouble with tips fitting your ear shape.

Yeah I totally agree. I get that people find them uncomfortable, but passive IEM's to me are way more comfortable than a heavy over-ear set which puts pressure against the sides of my skull. The noise canceling is also amazing without any electronics. Only trick is getting really good drivers in such a small space but IEM manufactures have been doing this for decades with great results.

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