11 Jun
2010
11 Jun
'10
2:44 p.m.
On 06/11/2010 02:10 PM, Ralf Mardorf wrote:
Olivier Guilyardi wrote:
Yes, you're right, the noises are obvious.
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.
Here I didn't need to listen carefully, it's unmistakable. I know this
kind of noise when doing recordings with anlog consumer cassette
recorders and cheap microphones and cables. Listen carefully and you will here this or similar
pulsations for the
sine wave too, perhaps just some background noise, when the sine was
recorded.
I think these are background noises. It has been recorded by putting the phone
near the computer speaker. I'd swear that this is murmuring in the background.
What happens for recordings without microphones?
There is no line-in, only a TRRS jack for both input and output. So I don't see
how to record without a mic. The user has tried to plug a headset with an
integrated microphone, and he said that the noises were still here.
He also reported the following: "if I rig up a TRRS 3.5 mm jack to XLR adapter
and use a "real" microphone the recording seems to be clean (though with other
issues, perhaps ground loops or impedance mismatch or something)".
I've seen similar problems when plugging an external microphone. That produced a
huge constant noise. I doubt that the user can really determines if the
pulsations are gone in this situation.
On the software side, couldn't a sample rate conversion produce that kind of
pulsations? I'm not doing any, but I haven't checked Android sources about this.
--
Olivier