Eric L. Strobel (fyzycyst_at_home.com) wrote:
> Now, if the frequency of the
> oscillation is higher than the fundamental mode of the resonating structure,
> then LOWER harmonics _of the fundamental mode_ can get excited. I believe
> this is what is being referred to.
Jon Glass's original claim was this:
> Secondly, no sound exists alone. Each sound creates
> harmonics. A 20khz sound creates harmonics both upward and downward into
> definitely audible hearing range. These harmonics work off of other sounds
> and frequencies. The sudden cutoff on early CDs created a very audible, and
> fatiguing (over long periods of time) artifact.
If an instrument resonates at a base frequency well above 20 kHz (which
we cannot possibly hear), but at the same time excites other oscillations
at lower frequencies -- whether these are properly referred to as
harmonics or merely resonance doesn't matter --, these oscillations most
likely _can_ be heard. But as the frequencies of these oscillations are
below 1/2 the sampling frequency specified by the Red Book standard, they
will also be captured on CD recordings. Therefore, there won't be any
artifacts, not because of this phenomenon anyway. (Of course, aliasing
artifacts could occur if no low-pass filter was used to cut off any
frequencies above 1/2 the sampling rate. Otherwise, frequencies slightly
above 1/2 the sampling rate would be recorded as the difference between
the original frequency and the sampling rate.)
- Michael
Michael J. Hussmann
E-mail: michael_at_michael-hussmann.de
WWW: http://michael-hussmann.de
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