#79 Adjusting the Spectral Envelope Evolution of Transposed Sounds with Gabor Mask Prototypes

Audio-samplers often require to modify the pitch of recorded sounds in order to generate scales or chords. This article tackles the use of Gabor masks and their capacity to improve the perceptual realism of transposed notes obtained through the classical phase-vocoder algorithm. Gabor masks can be seen as operators that allows the modification of time-dependent spectral content of sounds by modifying their time-frequency representation. The goal here is to restore a distribution of energy that is more in line with the physics of the structure that generated the original sound. The Gabor mask is elaborated using an estimation of the spectral enveloppe evolution in the time-frequency plane, and then applied to the modified Gabor transform. This operation turns the modified Gabor transform into another one which respects the estimated spectral enveloppe evolution, and therefore leads to a note that is more perceptually convincing.