[Top] [All Lists]

RE: Re: Questions for audio gurus

Subject: RE: Re: Questions for audio gurus
From: "Allen Cobb" <>
Date: Fri, 24 Feb 2006 11:31:10 -0600
Rich wrote:

> Am I correct that what you discribe as anti-aliasing
> artifacts will vary dependent on the quality of your
> a/d and d/a converters?

Absolutely! The D/A is the final link in the aliasing chain. Not
only the quality, but specifically the RATE at which the D/A can
operate. That's why a lot of ad hoc experiments with higher
samplerates don't test what they think they're testing. But it's
perfectly true, as Julius pointed out, that with the majority of
musical program material the aliasing "reads" as something
acceptable (or even something desirable).

The thing is, a very slight phase shift (read: delay) of a
signal near the Nyquist limit can cause the input signal to
disappear completely. It's not just a matter of being unable to
discriminate the wave SHAPE.

The accumulation of harmonic alias tones in a square wave sweep
is so blatantly audible that, as I originally said, it is
*unsettling* to conclude that it's all just irrelevant. Maybe in
a practical sense it IS irrelevant, but I find it unsettling.

And on the analog side, there is also plenty of amplifier and
speaker distortion that is quite horrible, although we've become
accustomed to it (and may even pay extra for it).

We have lived so long with 24-frame movie projection that the
flicker is considered irrelevant. But if you've ever seen a 50
frame per second projection, you'll wonder why we ever put up
with 24.


Allen Cobb

-----Original Message-----
 Behalf Of Rich Peet
Sent: Thursday, February 23, 2006 11:48 AM
Subject: [Nature Recordists] Re: Questions for audio gurus

--- In  "Julius Thyssen"
<> wrote:


> "Allen Cobb" <> wrote:

> Also, say you have a samplerate of 44.1 kHz
> and a source 24 kHz tone will be picked up
> by your microphone and amps;
> This will cause a not so loud anti-aliasing artifact
> around 20 kHz. Many of us will translate the artifact
> as "warm and airy", not as cold digital distortion.
> --
> Julius

"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
Yahoo! Groups Links


<Prev in Thread] Current Thread [Next in Thread>

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the naturerecordists mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the archive e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU