Relative Contributions of Amplitude and Phase to the Intelligibility Advantage of Ideal Binary Masked Sentences

Many studies have shown the advantage of using ideal binary masking (IdBM) to improve the intelligibility of speech corrupted by interfering maskers. Given the fact that amplitude and phase are two important acoustic cues for speech perception, the present work further investigated the relative contributions of these two cues to the intelligibility advantage of IdBM-processed sentences. Three types of Mandarin IdBM-processed stimuli (i.e., amplitude-only, phase-only, and amplitude-and-phase) were generated, and played to normal-hearing listeners to recognize. Experiment results showed that amplitude- or phase-only cue could lead to significantly improved intelligibility of IdBM-processed sentences in relative to noise-masked sentences. A masker-dependent amplitude over phase advantage was observed when accounting for their relative contributions to the intelligibility advantage of IdBM-processed sentences. Under steady-state speech-spectrum shaped noise, both amplitude and phase-only IdBM-processed sentences contained intelligibility information close to that contained in amplitude-and-phase IdBM-processed sentences. In contrast, under competing babble masker, amplitude-only IdBM-processed sentences were more intelligible than phase-only IdBM-processed sentences, and neither could account for the intelligibility advantage of amplitude-and-phase IdBM-processed sentences.