Patent US 7,124,075

Methods and apparatus for detecting periodicity and/or for determining the fundamental period of a signal such as speech. The methods include embedding a portion of a sampled digitized signal into an m-dimensional state space to obtain a sequence of m-dimensional vectors, selecting closest pairs of vectors in state space from a plurality of possible pairs of m-dimensional vectors in said sequence of m-dimensional vectors, accumulating total numbers of selected closest pairs of vectors having the same time separation values to produce a histogram of accumulated numbers, and locating at least a highest peak in a portion of said histogram to obtain a value indicating the fundamental period of the signal. Various embodiments are directed to speech and audio signal processing and other speech related applications. However, the methods have a general nature and can be applied to other types of periodic or quasi-periodic signals as well.