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Collaboration, Voice & AV · Foundational

Nyquist Theorem

The rule that a signal must be sampled at least twice its highest frequency to be reconstructed accurately.

Definition

The Nyquist-Shannon sampling theorem states that the sampling rate must exceed twice the highest frequency component to avoid aliasing. Because the telephone voice band extends to about 4 kHz, telephony samples at 8000 times per second. Professional audio uses 44.1 kHz or 48 kHz sampling to capture the roughly 20 kHz limit of human hearing.

Example

Wideband G.722 samples at 16 kHz to capture audio up to about 7 kHz.

Exam tip

If asked how many samples per second G.711 uses, answer 8000, derived from Nyquist and a 4 kHz voice band.

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