Results on perceptual invariants to transformations on speech

This paper presents results of a study on perceptual invariants to transformations on the speech signal. A set of psychoacoustic tests were conducted as to put forward these invariants for the human hearing system (HS). The starting point is the decomposition of speech by an AM-FM analysis, rather than the use of more standard analysis methods. The main result of this work is the finding that our HS is robust to-namely our perception is not altered by instantaneous frequency (IF) changes within a certain range, even though these resulted in substantial waveform modifications. This stimulated us to conduct further study on how standard analysis methods would cope with perceptually invariant changes; results show that, in fact, they are not robust to such changes. Finally, some applications of IF changes are proposed