[Peetwo]

P2

What I am suggesting, is that the mask may have been on, whilst still pressurised, almost certainly for the second "maintaining FL350", but it could be either way at the hand-off. In any case, if he had already slowly, not explosively depressurised, by the time of the hand-off, would he not be able to talk pretty normally ?  

The sounds of pressure breathing would be a give away, if he had to breathe, but for the brief transmission at the hand-off, "Good night, Malaysian Three Seven Zero", he would have said that in one single exhale cycle, so no inhale cycle recorded, so little if any, perhaps very subtle "signal" evidence for the spectral analysis.  Thus many many test subjects may be required to build a database good enough to pick it out of the signal noise, so to speak.

Acoustics is not my thing though, just throwing around "though bombs".

What do you think of that ?

From my experience talking through the mask mic sounds distinctively muffled whether on 100% or NORM.

It would also be easy enough to reinflate quick don (release head pressure) talk on headset mic or handheld & then deflate/refit mask. Probably 1-2 seconds longer than the TX call.

Definitely not much risk if a/c was slowly depressurising or on a max cabin altitude schedule.

P2