Quadratic detectors for general nonlinear analysis of speech

General quadratic detectors are defined and linked to the discrete-time version of Teager´s model (1980), to quadratic (also known as bilinear) time-frequency representations, and to other theory. As demonstrated on speech, these detectors have resolution advantages in simultaneous frequency selectivity and temporal resolution over linear detectors. Preprocessing for pitch detection using the detector is investigated, and it is shown that fast preprocessing for pitch tracking can be obtained by a suitable choice of coefficients. Simple speaker-independent phoneme classification based on a quadratic preprocessor and an artificial neural network is also examined, and comparative results indicate that a quadratic preprocessor facilitates the accurate estimation of waveform features. The preliminary results also suggest that these waveform features may provide useful information for fine phonetic distinctions