Zero-crossing rate

The zero-crossing rate is the rate of sign-changes along a signal. This feature has been used heavily in both speech recognition and music information retrieval and is defined formally as

$zcr = \frac{1}{T} \sum_{t=0}^{T-1} {{\mathbb I}\left\{{s_t s_{t-1} < 0}\right\}}$

where $s$ is a signal of length $T$ and the indicator function ${{\mathbb I}\left\{{A}\right\}}$ is 1 if its argument $A$ is true and 0 otherwise.

For monophonic tonal signals, the zero-crossing rate can be used as a primitive pitch detection algorithm.

[edit] See also

Fabien Gouyon, Francois Pachet, Olivier Delerue (2000), On the Use of Zero-Crossing Rate for an Application of Classification of Percussive Sounds, in Proceedings of the COST G-6 Conference on Digital Audio Effects (DAFX-00), Verona, Italy, December 7-9, 2000. Accessed 7th Oct 2006.