Modulation Enhancement of Temporal Envelopes for Increasing Speech Intelligibility in Noise

In this paper, speech intelligibility is enhanced by manipulating the modulation spectrum of the signal. First, the signal is decomposed into Amplitude Modulation (AM) and Frequency Modulation (FM) components using a high resolution adaptive quasi-harmonic model of speech. Then, the AM part of midrange frequencies of speech spectrum is modified by applying a transforming function which follows the characteristics of the clear style of speaking. This results in increasing the modulation depth of the temporal envelopes of casual speech as in clear speech. The modified AM components of speech are then combined with the original FM parts to synthesize the final processed signal. Subjective listening tests evaluating the intelligibility of speech in noise showed that the suggested approach increases the intelligibility of speech by 40% on average, while it is comparable with recently suggested state-of-the-art algorithms of intelligibility boosters.