Frequency-domain spectral envelope estimation for monophonic and polyphonic signals

摘要

Estimating the time-varying spectrum envelope of a time- varying signal facilitates pitch modification and other shifting of signal content in the frequency domain. Local maxima of a spectrum of the signal are identified by applying a masking curve. The masking curve has a peak at the particular maximum and descends away therefrom the local maximum. Local maxima falling below the local maximum are eliminated. The slope of the masking curve is varied in accordance with measured parameters of the spectrum to decrease or eliminate spurious peaks. Thereafter, a smoothing procedure may be applied to smooth the spectrum in frequency.