Re: [linux-audio-user] Re: 192kHz

From: Gene Heskett <gene.heskett@email-addr-hidden>
Date: Thu Jan 26 2006 - 23:21:22 EET

On Thursday 26 January 2006 15:47, Wolfgang Woehl wrote:
>bkhl@email-addr-hidden (Björn Lindström):
>> Wolfgang Woehl <tito@email-addr-hidden> writes:
>> > Ismael Valladolid Torres <ivalladt@email-addr-hidden>:
>> >> I don't see any reason to work at 192KHz. Apart from
>> >> huge files, Nyquist is on my side.
>> >
>> > Wouldn't interference of 2 or more signals from above the
>> > audible band have the potential to produce energy within
>> > the audible band?
>>
>> If so, you have already recorded it, haven't you?
>
>Discrete signals?

In a recording situation, there is always the possibility of aliasing,
and once thats in the digital data, it cannot be seperated by any other
means than a resample with a canceling phase signal. As the original
phase is unknown, there isn't much chance of ever getting it back out
of the data.

Aliasing is what happens when you record something with a doppler motion
detector running, and the recorder doesn't have a brick wall filter
thats at least 80 db down at half the sampling frequency and above.
The resultant playback will have a nominally .1 to 5 kilohertz tone
superimposed, and thats the diff between the 44.1khz sampling frequency
and the doppler burglar alarms normal running frequency.

Admittedly thats an extreme demo, but its a pretty good one if you'd
like to try it. It doesn't need more than a 5 dollar microphone
either.

Personally, I find aliasing distortion so unpleasant that I'll waste the
bandwidth and data storage to sample well above such man made racket.
But thats just me. YMMV.

-- 
Cheers, Gene
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Copyright 2005 by Maurice Eugene Heskett, all rights reserved.
Received on Fri Jan 27 00:15:22 2006

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