> Given that the anti-aliasing filter was sharp enough (in such a way
> that the 20 kHz is not being attenuated), then it should be possible
> to perfectly reconstruct the original 20 kHz signal and play it back
> without introducing any distortion.
Raimund,
My post crossed Gianni's with the link to an excellent article on
sampling. Put simply, a 20KHz sound is only sampled about twice per
waveform, and the position of those two points will vary. You can't
define even a simple sine wave with only two points which could be at
plus and minus extremes or near zero. If you zoom in on a sound editor
you will see a ragged trangular shape between the sampling points.
Noise is worse and various forms of distortion are also present,
expecially when there are other high frequency sounds present. Six
points per waveform will give you a cleaner but still far from perfect
result but that's about 7KHz with sampling at 44.1Khz.
Best Wishes, David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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