On Thu, 19 Aug 2004 11:03:32 -0400, "Arny Krueger"
wrote:

......some stuff deleted.....

I'm
sure Arny has the equipment more readily available - and may even have
.wav files for your listening pleasure, so you can hear for yourself
what the effects are.

Slightly different context, but its all FM:

http://www.pcabx.com/technical/jitter_power/index.htm

What would be really nice, is to frequency shift
a chunk of music with different delta-freq, and different modulation
frequencies, i.e., varying M with different conditions. Multi-tone and
real music should the preferred way to check this out.


I tried listening to your jitter samples in a less than optimum
environment. You have some castanet samples castanets-060.wav
(unjittered) and castanets_060_jit-20FF2.wav (-20 db 60 Hz jitter). I
can barely tell them apart. To my ears, the jitter version is slightly
duller, but the difference is so tiny, I could easily be fooled. All
the other samples are far too similiar to the reference.
Your piano selections (piano1_1644.wav [unjittered] and
piano1_1644_-20FF2.wav [-20db 60 Hz jitter])are indistinguishable to
me. I noticed that they are both distorted somewhat, nowhere as nice
as your reference piano_nlref.wav file.
Either my ears are totally wrecked (not likely), but the jitter
(FM) page you have really makes the case that it is not a very big
deal. From your spectral analysis, most of the crud is very close to
the fundamentals, and as such will be largely masked. Have you
synthesized higher or lower frequency jitter components to see their
audibility?
What is the prevaling opinion about the jitter (or FM "distortion")
samples you put on your site?
From my own testing, the sidebands need to be more like -10db (or
-10 db jitter as you specify it) before they begin to be audible.
That's pretty disgusting! 30% crud! Masking theory does confirm what
my ears tell me, namely that junk very close to the fundamental is
very well masked i.e., inaudible. It interesting that conventional
spectrum analyzers have the same difficulty. The ear does have much of
the behaviour of a poor dynamic range (30db) spectrum analyzer, with
strange post processing and AGC.
Readers of this newsgroup would be well advised to read up about the
ear (especially the cochlea) to understand masking and other
mechanisms the ears uses as "garbage cleanup".

-Paul
.................................................. .............
Paul Guy
Somewhere in the Nova Scotia fog