The Nyquist Frequency is the highest frequency that can be represented by a digital system. It is exactly 1/2 of the sample rate. Frequencies above the Nyquist Frequency will be incorrectly represented in the digital system. Frequencies above the Nyquist Frequency alias (or fold back) into the region below the Nyquist frequency. A frequency 1 kHz above the Nyquist Frequency will fold back to 1 kHz below the Nyquist Frequency. Likewise a frequency 2 kHz above the Nyquist Frequency will fold back to 2 kHz below the Nyquist Frequency.

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