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I've always wanted to ask an audiologist whether "active noise cancelling" type technologies actually pose an auditory risk. They kind of have to emit the same

I've always wanted to ask an audiologist whether "active noise cancelling" type technologies actually pose an auditory risk. They kind of have to emit the same amplitude-at-the-ear of audio of what they're cancelling out, right? And sure, most of the time the waves cancel, but maybe the algorithm gets it wrong a couple milliseconds at a time and - while possibly not perceptible - are those high peaks of audio-cancelling-sound damaging?

vages 6y ago
These "peaks" should all be within what you are able to hear, because there's no reason for having the headset produce cancelling waves with supersonic frequencies. If you want to worry about sudden sounds, there are probably more dangerous sources of them out there.
- addcninblue 6y ago
  That's only the produced sound, right? If the produced sound is at a frequency that coincides with the original sound (as opposed to being half a wavelength off), wouldn't it amplify the sound and make it up to 2x? Apologies if I misunderstood your comment.
  - lukevp 6y ago
    I am not an audiologist... but I don’t think it would result in 2x the sound. I believe a sound originating from 2 sources with the same amplitude results in either phase cancellation or the same resulting amplitude, not 2x. This is similar to what happens with line arrays.
    - addcninblue 6y ago
      I don't think so? This is classic wave interference right? https://en.wikipedia.org/wiki/Wave_interference https://en.wikipedia.org/wiki/Wave_interference
    - vages 6y ago
      You are thinking about the volume. As another replier said, two interfering frequencies produce an interference wave equal to their difference, so you can't have supersonic waves from something only capable of producing 20kHz sound
spockz 6y ago
This is anecdotal but I do feel a sense of pressure when using the Bose QC35. This pressure lasts for 30-60m when I’ve used them all day. I also have my ears popping after using them.
- thomasqm 6y ago
  I noticed the same. Disabling or lowering noise cancellation in-app fixed everything.
- Ekaros 6y ago
  I too feel it. Then again it might make sense that even if we don't hear it, the pressure is still there. As conservation of energy. After all active noise cancelling is destructive interference. Which has funny meaning that the energy is actually doubled. As we produce noise of equal power but opposite phase. Now does the energy end up in your ear or the headphone or outside? Or is it divided between these.
  - Baeocystin 6y ago
    The energy is dissipated as heat in the speaker coils. Energy is removed from the air. Think of it as using brakes to slow down a car. Yes, energy is consumed to do so (that's why the rotors get hot), but the car doesn't have 'hidden' energy, just because it was both accelerated, then decelerated. It really is at rest. The energy it embodied while in motion has been converted into other forms.
- jiofih 6y ago
  This is one the most popular topics in the Sony vs Bose war. For reasons I haven’t seen any explanation for, Sony headphones have much less of that vacuum feeling.
  - Cu3PO42 6y ago
    Anecdotally I strongly agree. I notice no such feeling at all when using my WH1000-XM3, but it's very perceivable when wearing the QC35 or QC25. I have tinnitus, but I've had it for way longer than I've been using noise cancelling headphones or in-ear earbuds.
Someone 6y ago
Unless the active noise cancelling gets it spectacularly wrong, the high peaks won’t be higher than the peaks in the to-be-cancelled noise. So, you’d have to argue that short, sudden peaks are more damaging than continuous sounds. There is adaptation to sound volume (https://asa.scitation.org/doi/10.1121/1.1906477 https://asa.scitation.org/doi/10.1121/1.1906477), but I think you’d need more than that.
maeln 6y ago
The thing is, noise cancelling is a very simple physical process. If it "miss" you will ear it. So there is no invisible danger, it cannot be not perceptible, either it cancel, or it add to the noise. The worst that ANC can do is add noise to the noise. Plus, most ANC focus on low frequency sound since they are the easiest one to cancel.
- ckemere 6y ago
  This assumes that active noise cancellation doesn't introduce energy in audible parts of the pressure spectrum.
  - stouset 6y ago
    This is no more a risk than normal audio you listen to doing the same.
    - sudosysgen 6y ago
      Of course not. If your driver is trying to cancel 95dB and creating a harmonic then that harmonic has 100 000 times more energy than the same harmonic when playing at 80dB without noise cancelation.
- trhway 6y ago
  > If it "miss" you will ear it. So there is no invisible danger, it cannot be not perceptible not always true. Minor phase mismatch will create higher frequency sound. You wouldn't hear ultrasound, though how bad it is to have an ultrasound source in you ears i don't know. The phase mismatch can be temporal - circuitry reacting either a bit too fast or too slow - as well as spatial - the sound wave front most probably aren't parallel to the speakers frontal plane.
  - nyanpasu64 6y ago
    A noise-cancelling system can be designed to filter out and not produce high-frequency sound, to not worsen the problem. I'm not sure if properly designed noise cancelling can produce increased pressures felt by any parts of the eardrum or ear canal or outer ear.
someonehere 6y ago
Ten years ago I was interested in buying Bose noise cancelling headphones. Someone warned me that they had read somewhere on the internet that noise cancelling creates problems with your hearing. At the time I couldn’t find anything on Google about this, but I still bought the headphones anyway. Using the headphones the lingering thought of that statement bothered me. Using the headphones something didn’t feel right. Flash forward to now, people are talking about this so I can’t find relevant info on this without the well (Google) being poisoned by armchair doctors. I still feel noise cancelling is not healthy for ears.
- jiofih 6y ago
  I feel like WiFi is damaging my brain /s
  - jensvdh 6y ago
    My Sony MXH100 headphones gave me tinnitus..
jiofih 6y ago
There is a running conspiracy theory that manufacturers found out about possible damage around 2018, and coincidentally all the popular models like the Sony WH1000 got firmware upgrades that perceivably downgraded the quality of ANC. I have a model from 2016 and can easily tell the difference from a newer one, now if that is the real reason or not... we’ll find out in the coming decade.
- fauria 6y ago
  This theory was brought up during a previous thread on HN by @novok, in response to https://news.ycombinator.com/item?id=22080228 https://news.ycombinator.com/item?id=22080228 I wonder... would this be theoretically possible? If so, are there any peer-reviewed papers published?
- jensvdh 6y ago
  I got tinnitus after using Sony WH1000 noise cancelling headphones in 2018. Damn...
- castratikron 6y ago
  I have a pair of those. I really like them except that they don't quite fit my ears and wearing them for more than a couple hours causes some soreness. If it weren't for that I'd probably wear them all the time. So, maybe that ended up saving me in the end.
ryanmarsh 6y ago
Yes they cause a number of problems. I experience nasty sinus headaches after prolonged use in loud environments (where the speaker driver is having to match the high amplitude of external noise).
Maxburn 6y ago
Mistakes in the cancelling might make peaks outside of human audible ranges that cause problems? I'm speculating here but wondering if anyone is looking into this.
fortran77 6y ago
I find active cancelling headphones to be very unpleasant. I've switched to custom molded in-ear monitors which do an even better job of eliminating external sound (musicians wear them on-stage to protect their hearing), sound better, and don't bother me the way active cancelling earphones do. I have no idea if active headphones are "bad", just that they make me feel very uneasy. The downside is that Custom In Ear Monitors are pricy (> $1000). When you have them made, you can often choose how many db of ambient sound attenuation you want.

vages 6y ago

These "peaks" should all be within what you are able to hear, because there's no reason for having the headset produce cancelling waves with supersonic frequencies. If you want to worry about sudden sounds, there are probably more dangerous sources of them out there.

addcninblue 6y ago
That's only the produced sound, right? If the produced sound is at a frequency that coincides with the original sound (as opposed to being half a wavelength off), wouldn't it amplify the sound and make it up to 2x? Apologies if I misunderstood your comment.
- lukevp 6y ago
  I am not an audiologist... but I don’t think it would result in 2x the sound. I believe a sound originating from 2 sources with the same amplitude results in either phase cancellation or the same resulting amplitude, not 2x. This is similar to what happens with line arrays.
  - addcninblue 6y ago
    I don't think so? This is classic wave interference right? https://en.wikipedia.org/wiki/Wave_interference https://en.wikipedia.org/wiki/Wave_interference
  - vages 6y ago
    You are thinking about the volume. As another replier said, two interfering frequencies produce an interference wave equal to their difference, so you can't have supersonic waves from something only capable of producing 20kHz sound

spockz 6y ago

This is anecdotal but I do feel a sense of pressure when using the Bose QC35. This pressure lasts for 30-60m when I’ve used them all day. I also have my ears popping after using them.

thomasqm 6y ago
I noticed the same. Disabling or lowering noise cancellation in-app fixed everything.
Ekaros 6y ago
I too feel it. Then again it might make sense that even if we don't hear it, the pressure is still there. As conservation of energy. After all active noise cancelling is destructive interference. Which has funny meaning that the energy is actually doubled. As we produce noise of equal power but opposite phase. Now does the energy end up in your ear or the headphone or outside? Or is it divided between these.
- Baeocystin 6y ago
  The energy is dissipated as heat in the speaker coils. Energy is removed from the air. Think of it as using brakes to slow down a car. Yes, energy is consumed to do so (that's why the rotors get hot), but the car doesn't have 'hidden' energy, just because it was both accelerated, then decelerated. It really is at rest. The energy it embodied while in motion has been converted into other forms.
jiofih 6y ago
This is one the most popular topics in the Sony vs Bose war. For reasons I haven’t seen any explanation for, Sony headphones have much less of that vacuum feeling.
- Cu3PO42 6y ago
  Anecdotally I strongly agree. I notice no such feeling at all when using my WH1000-XM3, but it's very perceivable when wearing the QC35 or QC25. I have tinnitus, but I've had it for way longer than I've been using noise cancelling headphones or in-ear earbuds.

Someone 6y ago

Unless the active noise cancelling gets it spectacularly wrong, the high peaks won’t be higher than the peaks in the to-be-cancelled noise. So, you’d have to argue that short, sudden peaks are more damaging than continuous sounds. There is adaptation to sound volume (https://asa.scitation.org/doi/10.1121/1.1906477 https://asa.scitation.org/doi/10.1121/1.1906477), but I think you’d need more than that.

maeln 6y ago

The thing is, noise cancelling is a very simple physical process. If it "miss" you will ear it. So there is no invisible danger, it cannot be not perceptible, either it cancel, or it add to the noise. The worst that ANC can do is add noise to the noise. Plus, most ANC focus on low frequency sound since they are the easiest one to cancel.

ckemere 6y ago
This assumes that active noise cancellation doesn't introduce energy in audible parts of the pressure spectrum.
- stouset 6y ago
  This is no more a risk than normal audio you listen to doing the same.
  - sudosysgen 6y ago
    Of course not. If your driver is trying to cancel 95dB and creating a harmonic then that harmonic has 100 000 times more energy than the same harmonic when playing at 80dB without noise cancelation.
trhway 6y ago
> If it "miss" you will ear it. So there is no invisible danger, it cannot be not perceptible not always true. Minor phase mismatch will create higher frequency sound. You wouldn't hear ultrasound, though how bad it is to have an ultrasound source in you ears i don't know. The phase mismatch can be temporal - circuitry reacting either a bit too fast or too slow - as well as spatial - the sound wave front most probably aren't parallel to the speakers frontal plane.
- nyanpasu64 6y ago
  A noise-cancelling system can be designed to filter out and not produce high-frequency sound, to not worsen the problem. I'm not sure if properly designed noise cancelling can produce increased pressures felt by any parts of the eardrum or ear canal or outer ear.

someonehere 6y ago

Ten years ago I was interested in buying Bose noise cancelling headphones. Someone warned me that they had read somewhere on the internet that noise cancelling creates problems with your hearing. At the time I couldn’t find anything on Google about this, but I still bought the headphones anyway. Using the headphones the lingering thought of that statement bothered me. Using the headphones something didn’t feel right. Flash forward to now, people are talking about this so I can’t find relevant info on this without the well (Google) being poisoned by armchair doctors. I still feel noise cancelling is not healthy for ears.

jiofih 6y ago
I feel like WiFi is damaging my brain /s
- jensvdh 6y ago
  My Sony MXH100 headphones gave me tinnitus..

jiofih 6y ago

There is a running conspiracy theory that manufacturers found out about possible damage around 2018, and coincidentally all the popular models like the Sony WH1000 got firmware upgrades that perceivably downgraded the quality of ANC. I have a model from 2016 and can easily tell the difference from a newer one, now if that is the real reason or not... we’ll find out in the coming decade.

fauria 6y ago
This theory was brought up during a previous thread on HN by @novok, in response to https://news.ycombinator.com/item?id=22080228 https://news.ycombinator.com/item?id=22080228 I wonder... would this be theoretically possible? If so, are there any peer-reviewed papers published?
jensvdh 6y ago
I got tinnitus after using Sony WH1000 noise cancelling headphones in 2018. Damn...
castratikron 6y ago
I have a pair of those. I really like them except that they don't quite fit my ears and wearing them for more than a couple hours causes some soreness. If it weren't for that I'd probably wear them all the time. So, maybe that ended up saving me in the end.

ryanmarsh 6y ago

Yes they cause a number of problems. I experience nasty sinus headaches after prolonged use in loud environments (where the speaker driver is having to match the high amplitude of external noise).

Maxburn 6y ago

Mistakes in the cancelling might make peaks outside of human audible ranges that cause problems? I'm speculating here but wondering if anyone is looking into this.

fortran77 6y ago

I find active cancelling headphones to be very unpleasant. I've switched to custom molded in-ear monitors which do an even better job of eliminating external sound (musicians wear them on-stage to protect their hearing), sound better, and don't bother me the way active cancelling earphones do. I have no idea if active headphones are "bad", just that they make me feel very uneasy. The downside is that Custom In Ear Monitors are pricy (> $1000). When you have them made, you can often choose how many db of ambient sound attenuation you want.