📖 Audio Glossary

Nyquist Frequency

The highest frequency accurately captured at a given sample rate — equal to half the sample rate. Frequencies above this cause aliasing.

The Nyquist-Shannon sampling theorem states that a signal must be sampled at least twice the highest frequency it contains to be accurately reconstructed. For CD-quality 44.1 kHz, the Nyquist frequency is 22.05 kHz — above the range of human hearing. For 48 kHz, it is 24 kHz.

Anti-aliasing filters must remove all content above the Nyquist frequency before sampling. In practice, this means the filter starts rolling off slightly below Nyquist — a 44.1 kHz system actually captures up to ~20 kHz, with a transition band from 20–22.05 kHz where the filter attenuates.

Related Terms

Sample RateThe number of audio samples captured per second during digital recording — 44.1 kHz is the CD standard; 48 kHz is the video standard; 96 kHz is common for high-resolution audio.AliasingDistortion that occurs when a signal is sampled below the Nyquist rate — creates false, unwanted frequencies not present in the original.Brick-Wall FilterA digital low-pass filter with an extremely steep cutoff slope — prevents aliasing but adds latency.
← All glossary termsBuying guidesCompare prices