Nyquist Frequency
The Nyquist frequency is the bandwidth of a sampled signal, and is equal to half the sampling frequency of that signal. If the sampled signal should represent a continuous spectral range starting at 0 Hz, the Nyquist frequency is the highest frequency that the sampled signal can unambiguously represent.
Example
If a signal is sampled at 22050 Hz, the highest frequency that can be expected to be present in the sampled signal is 11025 Hz. Thus, to attain this expectation, the continuous signal should be run through a low-pass filter with a cut-off frequency below 11025 Hz; otherwise, the phenomenon of aliasing would be encounterd.
Example
If a signal is sampled at 22050 Hz, the highest frequency that can be expected to be present in the sampled signal is 11025 Hz. Thus, to attain this expectation, the continuous signal should be run through a low-pass filter with a cut-off frequency below 11025 Hz; otherwise, the phenomenon of aliasing would be encounterd.
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