5 ms·

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, e

by 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.
- kortilla 6y ago
  Phase mismatch won’t change frequency
- ants_a 6y ago
  What is the mechanism for this? From what I remember of signal processing, linear combination of waves of a specific frequency can only result in a combined signal of the same frequency but different phase and amplitude.
  - NathanielK 6y ago
    It's not just phase mismatch. There is error in the frequency domain, both from the digital processing going on and the physical characteristics of the driver.
NathanielK 6y ago
If you're trying to cancel out a loud 100dB+ environment, that means the driver needs to be blasting at at least 100dB. Any harmonic distortion in the headphones will be introduced relative this, as well as being in the higher frequencies where it's less noticable, but still may cause hearing loss. I've used ANC IEMs instead of proper hearing protection around loud machinery before and although it may have felt quieter, my ears still "rang" afterwards so I was causing permanent hearing damage. People who think ANC "sounds quieter" and use it instead of proper hearing protection (or just turn the music too loud) will definitely suffer hearing loss, though not directly because of the ANC. I am not an audiologist, but an interesting similar issue happens with our eyes. If you wear tinted lenses with no UV filter, your body will be happy that it looks darker, and open your iris more. Now since your iris is open more, you actually cause more UV damage to your eye without noticing. I remember this being a big story when polarized 3D movie glasses came out and people were keeping them on outdoors.
- chii 6y ago
  > If you're trying to cancel out a loud 100dB+ i dont think it's feasible to cancel out such loud noise using just ANC. A sealed, airtight headset (or those tight earplugs) would have to be used. If you're using ANC for such loud noises, you'd still hear the noise through your bones/face imho. For example, if a car beeped its horn at you while using ANC, i hear it. ANC is merely for constant low background noise like airplane engine.
  - NathanielK 6y ago
    ANC doesn't ever provide perfect isolation. If you see advertisements ANC it will say "blocks 99% of sound" or "cancels 99.9% of noise" which is equivalent to a 20dB and 30dB drop respectively. You're right though that it doesn't work as well at high volumes. The louder the noise, the more distortion in the microphone/amplifier/driver, so the efficacy of the noise cancelling is reduced. For example in this THD graph of the AirPod Pro's, at 100dB it adds approximately 3dB compare to the 90dBtest.[1] Going much louder and you'll start getting digital clippings as the built in amplifier won't have enough range. > . For example, if a car beeped its horn at you while using ANC, i hear it. Car horns are above 100dB, and at the frequency they are, APD only measures about 20dB of attenuation [2], so that only brings it down to 80dB, which is still very loud. > ANC is merely for constant low background noise like airplane engine. What I find very neat is that even though only 20-30dB of isolation is measured, many noises really do "go away". If you play around with ANC you'll realize that as the background noise gets louder, the white noise hiss from the ear piece gets louder. This mostly the result of error in the system, but this increase in background noise has the effect of masking any external sounds that make it through. I believe it also moves a lot of that energy to higher frequencies where you don't notice it. [1] https://www.rtings.com/headphones/1-4/graph#1625/4029 https://www.rtings.com/headphones/1-4/graph#1625/4029 [2] https://www.rtings.com/headphones/1-4/graph#1625/4053 https://www.rtings.com/headphones/1-4/graph#1625/4053

by maeln 6y ago

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.
kortilla 6y ago
Phase mismatch won’t change frequency
ants_a 6y ago
What is the mechanism for this? From what I remember of signal processing, linear combination of waves of a specific frequency can only result in a combined signal of the same frequency but different phase and amplitude.
- NathanielK 6y ago
  It's not just phase mismatch. There is error in the frequency domain, both from the digital processing going on and the physical characteristics of the driver.

NathanielK 6y ago

If you're trying to cancel out a loud 100dB+ environment, that means the driver needs to be blasting at at least 100dB. Any harmonic distortion in the headphones will be introduced relative this, as well as being in the higher frequencies where it's less noticable, but still may cause hearing loss. I've used ANC IEMs instead of proper hearing protection around loud machinery before and although it may have felt quieter, my ears still "rang" afterwards so I was causing permanent hearing damage. People who think ANC "sounds quieter" and use it instead of proper hearing protection (or just turn the music too loud) will definitely suffer hearing loss, though not directly because of the ANC. I am not an audiologist, but an interesting similar issue happens with our eyes. If you wear tinted lenses with no UV filter, your body will be happy that it looks darker, and open your iris more. Now since your iris is open more, you actually cause more UV damage to your eye without noticing. I remember this being a big story when polarized 3D movie glasses came out and people were keeping them on outdoors.

chii 6y ago
> If you're trying to cancel out a loud 100dB+ i dont think it's feasible to cancel out such loud noise using just ANC. A sealed, airtight headset (or those tight earplugs) would have to be used. If you're using ANC for such loud noises, you'd still hear the noise through your bones/face imho. For example, if a car beeped its horn at you while using ANC, i hear it. ANC is merely for constant low background noise like airplane engine.
- NathanielK 6y ago
  ANC doesn't ever provide perfect isolation. If you see advertisements ANC it will say "blocks 99% of sound" or "cancels 99.9% of noise" which is equivalent to a 20dB and 30dB drop respectively. You're right though that it doesn't work as well at high volumes. The louder the noise, the more distortion in the microphone/amplifier/driver, so the efficacy of the noise cancelling is reduced. For example in this THD graph of the AirPod Pro's, at 100dB it adds approximately 3dB compare to the 90dBtest.[1] Going much louder and you'll start getting digital clippings as the built in amplifier won't have enough range. > . For example, if a car beeped its horn at you while using ANC, i hear it. Car horns are above 100dB, and at the frequency they are, APD only measures about 20dB of attenuation [2], so that only brings it down to 80dB, which is still very loud. > ANC is merely for constant low background noise like airplane engine. What I find very neat is that even though only 20-30dB of isolation is measured, many noises really do "go away". If you play around with ANC you'll realize that as the background noise gets louder, the white noise hiss from the ear piece gets louder. This mostly the result of error in the system, but this increase in background noise has the effect of masking any external sounds that make it through. I believe it also moves a lot of that energy to higher frequencies where you don't notice it. [1] https://www.rtings.com/headphones/1-4/graph#1625/4029 https://www.rtings.com/headphones/1-4/graph#1625/4029 [2] https://www.rtings.com/headphones/1-4/graph#1625/4053 https://www.rtings.com/headphones/1-4/graph#1625/4053