1 Answers
The zero-crossing rate is the rate at which a signal changes from positive to zero to negative or from negative to zero to positive. Its value has been widely used in both speech recognition and music information retrieval, being a key feature to classify percussive sounds.
ZCR is defined formally as
where s {\displaystyle s} is a signal of length T {\displaystyle T} and 1 R < 0 {\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 between a pair of adjacent positive zero-crossings there must be a single negative zero-crossing.