Intelligibility of Speech in Noise: Investigating Contribution of Magnitude and Phase Spectra

2026-06-15

AI Summary

This study investigates the mechanisms underlying reduced speech intelligibility in noisy environments, with a focus on the differential susceptibility of consonant categories to noise and the independent contributions of magnitude and phase spectra. Through three subjective listening experiments conducted under white noise and multi-talker babble conditions, the intelligibility of speech reconstructed using only magnitude or only phase information was systematically evaluated. For the first time, this work enables a direct comparison of magnitude and phase contributions across distinct noise types, revealing that while magnitude spectra dominate intelligibility in clean speech, phase spectra exhibit greater robustness in noise. Among consonants, nasals are most vulnerable to degradation, whereas fricatives and approximants remain relatively stable. These findings underscore the critical role of phase information in noisy speech perception.

Abstract

It is well known that intelligibility of speech reduces in the presence of ambient noise. However, studies show that all sounds are not affected uniformly (or equally) and that vowels are more robust to noise than consonants. In this study, intelligibility of various consonants is assessed and analyzed in stationary white noise and non-stationary babble noise conditions. Specifically, this study investigates the individual contribution of magnitude and phase spectra of a given speech signal on human speech recognition of consonants in noisy conditions. In this regard, three experiments are carried out. In experiment 1, clean signal, signal reconstructed with only magnitude spectrum information (magnitude only signal) and signal reconstructed with only phase spectrum information (phase only signal) are assessed for intelligibility. In experiment 2, noise is added to clean speech. From noisy speech, phase only signal and magnitude only signal are reconstructed and intelligibility tests are performed for all these three signals. In experiment 3, noise is added directly to the magnitude only and phase only signals reconstructed from clean speech and their intelligibility is assessed. Results of these experiments show that magnitude spectrum contributes more to intelligibility in clean condition than phase spectrum, while information from phase spectrum is more robust in noisy conditions. It is also observed that, among consonants, nasals are more susceptible to noise whereas fricatives and approximants were observed to be comparatively more robust.

Problem

• speech intelligibility
• noise
• magnitude spectrum
• phase spectrum
• consonants

Innovation

• phase spectrum
• magnitude spectrum
• speech intelligibility
• noise robustness
• consonant perception