In digital signal processing, **sampling frequency** is the rate at which sampling is done. Sampling frequency is usually measured in hertz, or samples per second.

When converting from analog to digital, the analog signal must usually be sampled -- that is, measured or read -- at discrete intervals of time. The length of the interval depends on the application, but is limited by the Nyquist-Shannon sampling theorem. The sampling frequency is the inverse of this number: the smaller the interval, the higher the frequency, and, in general, higher frequencies imply higher-quality sampling.

In digital audio, common sampling rates are:

- 8000 Hz - telephone
- 44100 Hz - compact disc
- 48000 Hz - digital sound used for films
- 192400 Hz - DVD Audio and Super Audio CD

When analogue video is converted to digital video, a different sampling process occurs, this time at the pixel frequency. Some common pixel sampling rates are:

- 13.5 MHz - CCIR 601, D1 video

See also: