Originally Posted by StanD
Man, that's worse than hearsay, that's just loose anecdotal that some guys unloaded on the public. Lets say you pick a bass frequency of 200 Hz, that's pretty high for bass. The 20th harmonic would be at 4 kHz. I can multiply that by 10 and that'll be 40 kHz. Nyquist-Shannon means double the sample rate of what you want to sample, I can double the 4 Khz 3 times and still be below 44.1 kHz. So do you think that you can hear the 20th harmonic, I don't think so. I picked a very high frequency for the fundamental tone of a bass note and then picked a ridiculously high harmonic and still came in under 44.2 kHz. My example is beyond extreme and it still works out.
I can probably find another expert to say some other weird stuff as well. Not to mention that I'm an EE and know a thing or two. When it comes to audio there are so many stories going around to spin the heads of audiophiles in circles. Keep in mind, when people say stuff off the top of their heads that contradicts the same science that brings us audio products, we should be careful in what we accept as real.
Not to cause a huge arguement but the nyquist-shannon theory is for the absolute minimum representation of a frequency, not an accurate one. Sampling at exactly double the highest frequency turns a sine wave at that frequency into a triangular saw tooth wave of the same frequency. You need a much higher sample rate to get a realistic reproduction of the origional sound wave.
Just think about it, if you have a 1khz signal and you take a sample at 2khz you take one sample at the top extreme and one at the bottom. When you reconstruct it that makes for a striaght line from top extreme to bottom extreme, and back again. And that's assuming that the sample is matched perfectly with the tone, if it isn't you get worse effects coming into play, that's actually the best case possible for Nyguist-Shannon. It's actually possible to completely mute the tone if the sample is aligned at 180degrees to the best case. And anything between 180 and 0 degress phase difference will give you attenuation of the amplitude. It's a lot more complicated than you might think.
Even at 4 times the tone frequency you get a very messed up wave coming out of it. Yes DACs are designed to accomodate for this as much as possible, but they do it by making educated guesses. In reality we aren't dealing with pure sine wave tones which stay locked in at a nice constant frequency where we can just round things out and hope everything will be ok.
I'm not saying they are right, just saying I wouln't discard the opinion of two experts on the basis of basic and largly approximated thoery.
Anyway, this isn't a discusson for this thread. There's an entire sound science section of forum for that. While not an EE I am a mathematical physicist, so I also know a thing or two about sound waves ;)
Edited by yblad - 2/11/14 at 6:52pm