Oh, and it's not a "measure" of what's different between two voices (be they human or instrumental) producing a sound with a fundamental frequency at 440 Hz. They are two completely different waveforms. It's only the slowest part of the waveform that's cycling at 440 times a second. That's what gives any instrument its unique timbre.

But it is possible to digitally capture and accurately reproduce any of those sounds that exist below the Nyquist of the sampling system.
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Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris