Zero-crossing rate

The zero-crossing rate is the rate of sign-changes along a signal, i.e., the rate at which the signal changes from positive to negative or back.^[1] This feature has been used heavily in both speech recognition and music information retrieval, being a key feature to classify percussive sounds.^[2]

ZCR is defined formally as

displaystyle zcr=frac 1T-1sum _t=1^T-1mathbb 1 _mathbb R _<0(s_ts_t-1)

where $s$ is a signal of length $T$ and $displaystyle mathbb 1 _mathbb R _<0$ is an indicator function.

In some cases only the "positive-going" or "negative-going" crossings are counted, rather than all the crossings - since, logically, between a pair of adjacent positive zero-crossings there must be one and only one negative zero-crossing.

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

Applications[edit]

Zero crossing rates are used for Voice activity detection (VAD), i.e., finding whether human speech is present in an audio segment or not.

References[edit]

^ * Chen, C. H., Signal processing handbook, Dekker, New York, 1988

^ Gouyon F., Pachet F., Delerue O. (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 - DAFX-06), Verona, Italy, December 7–9, 2000. Accessed 26 April 2011.

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[1] * Chen, C. H., Signal processing handbook, Dekker, New York, 1988

[2] Gouyon F., Pachet F., Delerue O. (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 - DAFX-06), Verona, Italy, December 7–9, 2000. Accessed 26 April 2011.

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