Greenears
100+ Head-Fier
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According to http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem it is mathematically impossible to reconstruct a continuous time signal from a discrete one without aliasing.
If what you mean by smoothness is that the output shouldn't contain frequencies above .5 Fs, maybe that's your preference, but not mine. I don't care if ultrasonic frequencies get to my ears, as long as the signal is at the proper resolution, and phase-coherent with the original.
"If the Nyquist criterion is not satisfied, adjacent copies overlap, and it is not possible in general to discern an unambiguous X(f). " Directly from the wikipedia article you quote.
If you read it carefully, it says "If". As always on forums most people are not fully up to speed on the Nyquist criteria, they only focus on the Fs>=2B sampling rate, as I already stated above. I have tried to highlight them above, but again, the signal being sampled needs to band-limited, usually written as f = -B to B. It must have zero energy at f>B and f<-B. If that is satisfied you will not have aliasing. The Wikipedia article is correct, they have the correct criteria in the preceding paragraph.
You are also introducing questions about ultrasonics that have nothing at all to do with Nyquist. If you want frequencies up to 100 kHz that is fine, just sample at 200 kHz. But it must be bandlimited - ie no energy beyond 100 kHz otherwise you will have aliasing.