Robust speech representation of voiced sounds based on synchrony determination with PLLs

We propose to include synchrony effects, known to exist in the auditory system, to represent voiced parts of the speech signal in a robust way. The system decomposes the input signal by means of a bandpass filter bank, and utilizes a bank of phase locked loops (PLLs) to obtain information on the frequencies present at a specific time. This information about the frequency distribution is transformed into a spectral-like representation based on synchrony effects. Noisy speech recognition experiments are performed using this synchrony-based spectrum, which is transformed into a small set of coefficients by using a transformation similar to that utilized for mel cepstrum features. We show that recognition performance compared to mel cepstrum features is advantageous, when measured over a range of SNR conditions, especially in the high noise level case.