RE: Ask an Audio geek
April 12, 2016 at 11:35 pm
(This post was last modified: April 12, 2016 at 11:55 pm by Alex K.)
No no, it has nothing to do with the psychoacoustic effect (that's relevant for dropping in-between frequencies in mp3 compression), it has to do with the limited frequency range of hearing.
The point of the sampling theorem is that with a signal of limited highest frequency, these discrete points uniquely determine what goes on between them. If the signal you send in is cut off sharply at say 20 khz using a steep filter, it will not have any features which are so quick that they can be missed if you only measure 44100 times per second. Such a signal can only change its direction of up-down movement so fast, because changing faster would require containing higher frequencies. If you have ever seen what a low pass filter does to short pulses, it might become clearer.
The point of the sampling theorem is that with a signal of limited highest frequency, these discrete points uniquely determine what goes on between them. If the signal you send in is cut off sharply at say 20 khz using a steep filter, it will not have any features which are so quick that they can be missed if you only measure 44100 times per second. Such a signal can only change its direction of up-down movement so fast, because changing faster would require containing higher frequencies. If you have ever seen what a low pass filter does to short pulses, it might become clearer.
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition