AMDF Pitch Extractor
Harry L. Shaffer, M. Ross, A. Cohen · The Journal of the Acoustical Society of America · 1973
A method is described for estimating the fundamental frequency component of voiced speech using the Average Magnitude Difference Function (AMDF). The technique, a variation of autocorrelation analysis, uses a difference signal formed by delaying the input speech various amounts and subtracting the delayed waveform from the original. The difference signal is always zero at delay = ø, and exhibits deep nulls at delays corresponding to the pitch period for a voiced sound having a quasi-periodic structure. Unlike the generation of the autocorrelation function, the AMDF calculations require no multiplications, a desirable property for real-time speech processing. Also, since the computations involve numerous repetitive operations, they are very suitable for fabrication in special-purpose hardware. The implementation of the AMDF pitch extractor will be described and experimental results presented to illustrate the basic measurement properties.