Are noise-cancelling headphones damaging my hearing?
July 19, 2015 11:47 PM   Subscribe

According to my understanding of how noise-cancelling headphones work, the headphones detect low-frequency ambient noise levels near my ears, and emit a frequency which cancels out the ambient noise, so that instead I hear silence in place of the noise. Although I can't hear these noise-cancelling frequencies, I'm wondering whether they might be having a cumulative negative effect on my hearing. Is it only audible frequencies that have the potential to harm? Or can prolonged exposure to inaudible frequencies have a detrimental physical effect?
posted by paleyellowwithorange to Health & Fitness (9 answers total) 5 users marked this as a favorite
Best answer: What most of them do is emit the exact same frequencies they're getting as inputs, 180 degrees out of phase. This has the effect to the ear of cancelling them out, basically. It's low amplitude ambient noise they're filtering out, not low frequency.

So no, you don't have a potential for harm AFAIK.
posted by feckless fecal fear mongering at 12:24 AM on July 20, 2015 [6 favorites]

Best answer: The headphones work using active noise control. Sound waves are pressure waves and the mechanism works to reduce their physical amplitude (rather than, for example, masking out the problem sounds with something else that could be potentially damaging). The result should be that any music you play through the n/c headphones should need to be less loud than it would otherwise be so as to sound acceptable - which is good for your hearing. So - no, IMHO.
posted by rongorongo at 12:25 AM on July 20, 2015

Best answer: Sorry, meant to expand. Sound waves, like any wave, oscillate around a zero point (that's the amplitude; how far from the zero point the wave gets). They oscillate at a specific speed--that's the frequency. You can substitute 'volume' and 'pitch' if they make more sense to you; functionally it's the same thing. To a reasonable approximation, if you play something at a given frequency at identical positive and negative amplitude--that is by reversing the phase by 180 degrees--you're going to hear nothing.
posted by feckless fecal fear mongering at 12:31 AM on July 20, 2015 [1 favorite]

Best answer: Imagine a person wiggling one end of a rope, sending waves to the far end (your eardrum).

The noise cancellation headphones send little canceling waves to the rope right before a wave would hit your eardrum, cancelling them out, meaning less energy going to your ear. Meaning less potential damage.
posted by sebastienbailard at 1:20 AM on July 20, 2015

I have written about some of the side-effects of wearing noise-canceling headphones previously.
posted by seawallrunner at 3:47 AM on July 20, 2015

Best answer: Hey, I'm an audiologist and I talk about safe headphone use a lot.

The short answer, as others have pointed out, is no. Like others have said the headphones use phase cancellation to attenuate the level of ambient noise. Whether inaudible sounds can damage your hearing is a bit of a complicated issue, but the short answer is also generally no.

I actually favor noise-cancelling (or even better, passive sound attenuating earphones like deep insertion custom in-the-ear monitors) because generally these earphones allow people to keep the volume of the earphone lower, because they are not trying to turn the music up to mask the outside noise.

Generally speaking, damage to your hearing from sound is a combined effect of the intensity level of the sound (volume) and the length of time of exposure. So as long as your aren't turning up your headphones to unsafe levels, you should be fine. An unsafe level for earphones is at complete maximum 85 dB, though I like to cap it at 75-80 (this would be the level of someone shouting at you). There's really no good way to check the objective output level of your headphones without a sound level meter. Just don't crank the volume or listen for hours and hours (and if you do, give your ears a break for the rest of the day and be in silence).
posted by Lutoslawski at 8:18 AM on July 20, 2015 [11 favorites]

Just adding on to Lutoslawski's comment on volume safety, since we've established noise cancellation is not likely a source of damage.

While it is not an objective measurement, you may find this helpful for evaluating appropriate volume: start playing some reasonably loud/compressed music, and insert one in-ear-canal bud or clasp one side of your headphones to one ear, and with the other ear listen to a quiet conversation mid-way across the room. When the subjective levels match, you're good to go. Alternate ears each morning.

Pure passive In-ear-canal headphones hover around -24 to -28dB attenuation of ambient, so once you've got both in and have adjusted for a couple minutes this will be more than sufficient for reference-grade work.
(Source: used to grind through editing 20-30 thousand voiceover takes each month for stretches of 3-6 months).
posted by Ryvar at 1:20 PM on July 20, 2015

Best answer: Although I can't hear these noise-cancelling frequencies

The reason you can't hear them is not because they're fooling your ear in some way; it's because the noise-cancelling energy pumped into the headphone speakers physically opposes the noise vibrations in order to stop them actually getting past the phones to reach your eardrums. The physical effect is almost completely identical to what you'd get from wearing ordinary earphones under big thick heavy industrial-safety ear protectors, though obviously the comfort is much higher.
posted by flabdablet at 1:31 PM on July 20, 2015 [1 favorite]

No -- unless, of course, you are cranking the volume of the music you are listening to up to very high levels. Noise canceling cancels the background noise, not the signal you are trying to listen to, so standard headphone warnings still apply. Rock out too hard and you might damage your hearing, noise cancellation or not.

If you are just using the noise cancellation and aren't listening to anything else, then you're really listening to nothing but electronic noise at low level. Nothing there to harm.
posted by eriko at 6:00 AM on July 21, 2015

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