Importance of the Dynamic Range of an Analysis Windowfunction for Phase-Only and Magnitude-Only Reconstruction of Speech

The short-time Fourier transform (STFT) of a speech signal has two components: the short-time magnitude spectrum and the short-time phase spectrum. It is traditionally believed that the short-time magnitude spectrum plays the dominant role for speech perception at small window durations (20-40 ms). However, recent perceptual studies have shown that the short-time phase spectrum can contribute as much to speech intelligibility as the short-time magnitude spectrum. It was observed that the use of the rectangular (non-tapered) analysis window for the computation of the short-time phase spectrum is more advantageous than the use of the Hamming (tapered) analysis window. This paper investigates the effect that the dynamic range of an analysis window has on the intelligibility of speech for phase-only and magnitude-only stimuli. For this purpose, the Chebyshev analysis window with adjustable equi-ripple side-lobes is employed. Two types of magnitude-only stimuli are investigated: random phase and zero phase. It is shown that the intelligibility of the magnitude-only stimuli constructed with zero phase is independent of the dynamic range of the analysis window, while the random phase stimuli are intelligible only for analysis windows with high dynamic range. This study also shows that for low dynamic range analysis windows, the short-time phase spectrum at small window durations (20-40 ms) contributes as much as to speech intelligibility as the short-time magnitude spectrum.