Hey Tony,

My friend Ash and I (check out his two car computers ) have had an on-going debate regarding the quality of 128kb mp3's vs. higher.. I forwarded your post to him, check out his response:

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This makes sense to me. Because higher frequencies have more waves per
second, it seems that the repetitiveness of these high frequencies are
harder for the compression algorithm to recognize and therefore you have
some degree of alternating sources of the repeat which will cause you to
hear a flanger-type effect in cheering, and most other high frequency
sound sources. But what this document doesnt explain is why some come
out sounding different whereas other cd's compress fine. 95% of music
is going to have low, mid, and high range frequencies. The high range
is the one in question because according to this, those high
frequencies are what create these anomolies but, all songs have high
frequencies. It may have to do with the CD itself and how purely those
high frequencies are recorded. Our ears may hear a perfect 8th octave
C note but the digital transcript on the CD would show some
inconsistencies in the wave pattern that the MP3 encoder will see and
translate that small inconsistent section as another repetitive cycle,
but unlike the moment before as a perfect 8th C. Therefore creating a
flanging effect by switching from one repetitive clip over to this short
inconsistent clip that almost sounds the same, but different, and then
back to the first clip once more. Imagine this happening at say, 20
times per second on one note. This will create a 20Hz flange that will
be audible. Of course, what I have said to be the source of this
(inconsistencies on the CD) is only a theory. I dont know if this is
actually the cause, but I think I'm on to something. BTW: 8th octave C
is actually the highest note on a piano at the far right. It is at
16KHz, pretty damn high.
Ash

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-mark

...proud to have one of the first Mark I units