"Perry E. Metzger" <perry@piermont.com> writes:
The Nyquist Theorem states you need exactly twice the samples, not over twice. The magic number isn't something like 2.2, its exactly 2.
The Sampling Theorem states that equally spaced instantaneous samples must be taken at a rate GREATER THAN twice the highest frequency present in the analog signal being sampled. If this is done, the samples contain all the information in the signal, and faithful reconstruction is possible. Exactly twice the highest frequency won't do, and it should be obvious that sampling a sine wave at twice its frequency yields samples of constant magnitude and alternating sign which convey nothing about its phase and little useful about its amplitude either. (Drawing a little picture might be helpful here.) Although anything over twice the highest frequency will work in a theoretical sense, a small fudge factor does wonders for digital signal processing, if only to reduce to a reasonable value the width of the window into the sample stream needed for various signal manipulations. -- Mike Duvos $ PGP 2.6 Public Key available $ mpd@netcom.com $ via Finger. $