Nyquist says that if you sample a repeating waveform, ANY repeating waveform, at a sampling rate greater than or equal to the highest frequency partial present in the waveform, you can exactly duplicate that waveform. Yes, exactly duplicate the original.
Lamar's comments are correct, but then, what difference is there between amplitude modulation at the sampling frequency and a partial at that frequency? Both contain information that cannot be captured by the stated sampling frequency. Why would you amplitude modulate anything that fast? -BobC -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of STEFFL, ERIK *Internet* (SBCSI) Sent: Friday, June 14, 2002 12:01 PM To: '[EMAIL PROTECTED]' Subject: RE: [linux-audio-dev] RFC: API for audio across network - inter-host audio routing > -----Original Message----- > From: Lamar Owen [mailto:[EMAIL PROTECTED]] ... > The idea is that you get the integrated value of the > amplitude of the sine > wave, since a sine wave always has the same shape. But the > amplitude, at the > Nyquist frequency, cannot change. Yes, I really said that. > If the amplitude > of the sine wave changes, you get an upper sideband above the > Nyquist rate > that you cannot sample -- of course you also get a lower > sideband that you > can sample, but then the recovered envelope is distorted. > Amplitude changes > at the Nyquist frequency violate Nyquist's theorem. Thus the Nyquist > frequency itself is an asymptote and cannot be accurately > reproduced except > in the steady state. nyquist theorem doesn't say that you can get EXACT same signal if your sampling frequency is twice the highest frequencey of signal. It says (roughly) that you wouldn't miss any bumps (of frequency half of your sampling frequency), you can't be sure about the shape of those bump (amplitude). which is basically what you say, it's just that there is no violation of nyquist theorem there... erik
