Re: Nyquist, quantization and windowing gotcha's

On Sep 4, 1:57 pm, Richard Owlett <rowl...@xxxxxxxxxxxxx> wrote:
mblume wrote:
Am Thu, 04 Sep 2008 11:34:52 -0500 schrieb Richard Owlett:

... recording of an arctic loon (ORIGINALLY recorded
at 22 kHz and saved as mp3).
[...]
*QUESTION*     Am I facing other "gotcha's"?

mp3 is a lossy compression based on human psychoacoustics, so
the signal is distorted. Saving as mp3 isn't a good idea for
later doing signal analysis (unless studying the effects of
mp3, of course ...).

IMHO. YMMV.
Martin

!!! *LOL* !!!
Should have mentioned that Rune had pointed that out in previous thread.
That's why I mentioned "prime" source was mp3 ;)
ALSO that's why I noted I was working with a 44k sample/sec copy when
original was 22k ;{

Other than lossy compression effects,
what are other GOTCHA's ????- Hide quoted text -

- Show quoted text -

Hello Richard,

One possible place for error is when the original contains frequencies
outside of normal human hearing or near its limits. I think the .mp3
approach uses a filter bank and if you are off of the ends of the
bank, you may lose some data.

I do note that your source is limited to a max frequency of only 11kHz
and practically it is maybe only 9 or 10kHz. I don't know if bird
calls normally contain frequencies of any significant strength above
10kHz. Cats can easily hear up to 60 kHz (kittens hear over 100kHz)
which is quite effective in localization of prey. Part of the high
frequency requirement for cats comes from their heads being small and
hence their ears close together. Birds (most) of course have even
smaller heads. Do they localize well with hearing or do they have to
rely on their amazing vision to locate things? Some birds like owls
seem to have quite sensitive ears and cat sized heads and they too
hunt rodents. I don't know much about loons. What do they hunt and
does hearing play a large part in that process?

Clay




.

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