Zero-crossing Rate
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The zero-crossing rate (ZCR) is the rate at which a
signal A signal is both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology. In ...
changes from positive to zero to negative or from negative to zero to positive. Its value has been widely used in both
speech recognition Speech recognition is an interdisciplinary subfield of computer science and computational linguistics that develops methodologies and technologies that enable the recognition and translation of spoken language into text by computers. It is also ...
and
music information retrieval Music information retrieval (MIR) is the interdisciplinary science of retrieving information from music. Those involved in MIR may have a background in academic musicology, psychoacoustics, psychology, signal processing, informatics, machine lear ...
, being a key feature to classify percussive sounds.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. ZCR is defined formally as :zcr = \frac\sum_^\left, \mathrm (t)\mathrm (t-1) where s is a signal of length T and \mathrm(x) is a sign function defined as: :\mathrm(x)=\begin1,\quad x\geq 0\\0, \quad x<0\end In some cases only the "positive-going" or "negative-going" crossings are counted, rather than all the crossings, since between a pair of adjacent positive zero-crossings there must be a single negative zero-crossing. For
monophonic Monaural sound or monophonic sound (often shortened to mono) is sound intended to be heard as if it were emanating from one position. This contrasts with stereophonic sound or ''stereo'', which uses two separate audio channels to reproduce sou ...
tonal signals, the zero-crossing rate can be used as a primitive
pitch detection algorithm A pitch detection algorithm (PDA) is an algorithm designed to estimate the pitch or fundamental frequency of a quasiperiodic or oscillating signal, usually a digital recording of speech or a musical note or tone. This can be done in the time do ...
. Zero crossing rates are also used for
Voice activity detection Voice activity detection (VAD), also known as speech activity detection or speech detection, is the detection of the presence or absence of human speech, used in speech processing. The main uses of VAD are in speaker diarization, speech coding an ...
(VAD), which determines whether human speech is present in an audio segment or not.


See also

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Zero crossing A zero-crossing is a point where the sign of a mathematical function changes (e.g. from positive to negative), represented by an intercept of the axis (zero value) in the graph of the function. It is a commonly used term in electronics, mathema ...
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Digital signal processing Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are a ...


References

Signal processing Rates {{Signal-processing-stub