[linux-audio-user] Re: 192kHz

[Gene Heskett]

On Thursday 26 January 2006 15:47, Wolfgang Woehl wrote:
>bkhl at elektrubadur.se (Björn Lindström):
>> Wolfgang Woehl <tito at rumford.de> writes:
>> > Ismael Valladolid Torres <ivalladt at punkass.com>:
>> >> 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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