[linux-audio-user] sampling at high frequencies

Steve Harris S.W.Harris at ecs.soton.ac.uk
Mon Jan 26 06:28:12 EST 2004


On Mon, Jan 26, 2004 at 11:54:26 +0100, Joern Nettingsmeier wrote:
> >This is not quite correct. While humans can not hear continuous tones over
> >20-odd kHz that is not the whole story, the frequency reproduction also
> >limits the minimum transient rise time, which is detected by a different
> >part of the ear (IIRC, IANABiologist and my psychoacoustics textbook is at
> >work).
> 
> interesting point. but isn't membrane inertia the limiting factor in 
> transient reproduction anyway?

Which membrane? The basilar membrane is responsible for frequency alaysis
(AFAIR), but its limited by its geometry. Doesn't it detect resonances in
the narrowing tube? Transients could be detected before the pressure wave
reaches the basilar membrane, though I'm just guessing here.
 
> my naive understanding is that min rise time = nyquist freq. if we 
> cannot perceive frequencies above, say, 20k, all we win by faster 
> sampling is more accurate timing information.
> but there is a worst-case "timing error" of 1/24000 sec, which does not 
> seem much to me...

Its not the timing error - it wont be quatised to the nearest sample
AFAIK, but you will get substantial ripple from the reconstruction filters
fi you try to reproduce transients near nyquist- dunno how that is perceived.

> i'd like to read more, but i haven't been able to google anything up 
> about transient perception and reproduction. any pointers?

There seems to be some relevent stuff here:
http://arjournals.annualreviews.org/doi/full/10.1146/annurev.neuro.23.1.285
but its a bit over my head.

> for the record, here's a 1998 aes paper that elaborates on the 
> consequences of higher sampling on filter artifaces in the audible 
> range: http://www.nanophon.com/audio/antialia.pdf

Thanks, thats interesting.

- Steve


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