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On a plane, as a passanger, I can't hear my own breath. I can't hear my own breath even in a silent room.

On a plane, there is a continous background noise.

And the microphone recording the noises in the cockpit, are probably not directly at the lungs of both pilots.

I am really wondering, how can the breath of a pilot simply be recorded on the cockpit, if it wasn't designed specifically for that (or it isn't a very high quality recorder placed directly to the body of the pilots)?

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    $\begingroup$ Breathe heavily onto a microphone. You'll definitely hear it (provided it doesn't have a filter to remove such noise.) I've certainly heard my own breath in my aviation headset plenty of times. $\endgroup$
    – reirab
    Commented Mar 27, 2015 at 14:46
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    $\begingroup$ @bjb568 Now I tested it. On normal circumstances, I can't hear it even in a silent room. But a little bit of elevated breathing intensity (for example, walking up a floor) makes it hearable. But on a mobile talk, I never hear the breath of the other side. $\endgroup$
    – Gray Sheep
    Commented Mar 27, 2015 at 23:53
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    $\begingroup$ @reirab It is true. But on mobile talk, I never hear the breath of the other side. $\endgroup$
    – Gray Sheep
    Commented Mar 27, 2015 at 23:54
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    $\begingroup$ @user8558 If they're breathing hard enough, you can hear it. Funny thing, we actually had that happen during a phone interview with a dev candidate once. Sounded like he was out of breath. You generally can't hear it with phones, though, since people usually hold the mic to the side of their mouth instead of directly in front. Aviation headsets usually have the mic directly in front of your mouth. $\endgroup$
    – reirab
    Commented Mar 28, 2015 at 0:26
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    $\begingroup$ @user8558: part of the reason for that is that mobile phone audio is heavily compressed, in ways cleverly designed to selectively discard information that "doesn't sound like a voice". But listen to any Muse song and you'll hear that good-quality microphones can pick up breathing ;-) $\endgroup$
    – Steve Jessop
    Commented Mar 28, 2015 at 3:26

3 Answers 3

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One of the channels of the Cockpit Voice Recorder is the microphone on each pilot's headset. This is much closer to the source of the breathing noise than your own ears. The microphone may also not have a wind filter so breathing on it will generate a lot of noise.

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Pilot's breath is not recorded on a flight data recorder, as it is not one of the data parameters.

However, if a pilot is breathing abnormally, the cockpit voice recorder may easily detect that as the breathing sound is captured by the CVR.

A reference to this can be found in the press conference summary for Germanwings flight 4U9525, which states:

... the only sound to come from Lubitz is the sound of him breathing, picked up by the microphone on his headphone set. ... “We could hear human breathing inside the cabin,” said Mr Robin, “and this breathing noise we heard up until the moment of final impact. That means that the co-pilot was alive. Apparently he was breathing normally, so this is not someone having a heart attack, for example.

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  • $\begingroup$ Someone having a heart attack wouldn't usually set the auto-pilot to an altitude of 100 feet over mountainous terrain. $\endgroup$
    – davidjwest
    Commented Mar 27, 2015 at 14:36
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    $\begingroup$ @davidjwest, No, but it would be conceivable for them to slump over onto the yoke (in an aircraft that has a yoke, at least.) $\endgroup$
    – reirab
    Commented Mar 27, 2015 at 14:44
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    $\begingroup$ I'm not sure why you mentioned the FDR? $\endgroup$
    – raptortech97
    Commented Mar 27, 2015 at 17:02
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You can actually hear breath on the mic (see ratchet freak's answer above). If you have multiple pilots, you can hear the other guy breathing on the channel intermittently. You do not hear every breath, just the sniffs, intakes, coughs, etc, all the little noises he makes.

In other words, when they say "breathing" for that incident, that includes all kinds of little noises that are associated with normal breathing.

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  • $\begingroup$ I wonder if perhaps the CVR records audio even when the squelch function is suppressing it from being played to the headsets (because no one is talking?) In that case, they'd probably be able to hear almost every breath on the recording. $\endgroup$
    – reirab
    Commented Mar 27, 2015 at 18:02
  • $\begingroup$ @reirab The CVR only records what is on the channel. Squelch is only applicable to received transmissions (which have noise). The pilots can hear each other clearly. As I said normally you can't hear somebody breathing, but you do hear little noises. For example, even if the other guy just opens his lips you might hear a tiny little smacking sound. Typically what you hear are: sharp intakes of breath, yawns, swallows, little coughs/throat clearing, sniffs/sniffles, sighs/heavy exhales. $\endgroup$
    – Tyler Durden
    Commented Mar 27, 2015 at 18:22
  • $\begingroup$ I haven't flown any airliners, but in the PA-28 I fly, there's a squelch on the mics just for intercom, too. It mutes when no one's talking in order to prevent background noise (and breathing noise) from being played in your ears constantly. It automatically unmutes above a certain volume level (e.g. when someone talks, breathes hard, coughs, touches the mic, etc.) There's a separate squelch for received transmissions on the COM radios. $\endgroup$
    – reirab
    Commented Mar 27, 2015 at 18:31
  • $\begingroup$ @reirab Now that you mention it, I guess there is a second squelch for the intercom. I usually turn that off because I find it difficult to get it exactly right. It is always cutting off the other guy's voice, especially if he says something softly. The CVR will obviously have no squelch, so anything you would hear with squelch off, I would expect to be on the CVR. $\endgroup$
    – Tyler Durden
    Commented Mar 27, 2015 at 18:40

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