[LAD] Looking for the cause of pulsating noises

Hello,

I have developed an audio recording application for Android, and a user is
reporting a weird noise issue. There are near-zero chances that this comes from
my code, and I'm looking for the possible cause of these noises.

Here is the sample, it's a musical flute and violin recording:
http://sound.samalyse.org/tapemachine/pulsations.wav

Listen carefully and you will here small pulsations.

I've also asked him to record a 440Hz sine. This one isn't distorted:
http://sound.samalyse.org/tapemachine/record440hz.wav

I suspect that this is a hardware issue, but I'm no expert so I can't really
tell. The phone is an HTC Incredible, which unless I'm wrong, means that the
sound components are embedded into a Qualcomm Snapdragon QSD8650 chip.

One other is that, although Android is a linux-based system, and use alsa
underneath, there's a terrible high-level Java API, which is full of various
problems which I have worked around to obtain that kind of quality. Thus, I
can't really tell what happens in there.

Have you already heard such things, and know what the cause, whether hardware or
software, is likely to be?

--
  Olivier
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