Shannon's Therorem (paraphrased) states that

" .. if the sampling is carried out at more than two times the

highest frequency in the signal before sampling, then the

signal can be reconstructed without degradation."

This is probably the most important concept in DSP.

It also implies that no frequency above half the sampling rate can be represented.

This comes into play when we want to synthesize signals in the digital domain.

Some signal processing techniques can generate new frequency components which violate this principle.

Common sampling frequencies are 44100Hz (Audio CD) and 48000Hz (Digital Audio Tape).

There is also a move towards higher sampling rates like 88100Hz (SACD?) 96000Hz (Audio DVD) and even 192000Hz.

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