Evaluation of near-end speech enhancement under equal-loudness constraint for listeners with normal-hearing and mild-to-moderate hearing loss

The effects of Lombard perturbation on speech intelligibility in noise for normal hearing and cochlear implant listeners

Natural compensation of speech production in challenging listening environments is referred to as the Lombard effect (LE). The resulting acoustic differences between neutral and Lombard speech have been shown to provide intelligibility benefits for normal hearing (NH) and cochlear implant (CI) listeners alike. Motivated by this outcome, three LE perturbation approaches consisting of pitch, duration, formant, intensity, and spectral contour modifications were designed specifically for CI listeners to combat speech-in-noise performance deficits. Experiment 1 analyzed the effects of loudness, quality, and distortion of approaches on speech intelligibility with and without formant-shifting. Significant improvements of +9.4% were observed in CI listeners without the formant-shifting approach at +5 dB signal-to-noise ratio (SNR) large-crowd-noise (LCN) when loudness was controlled, however, performance was found to be significantly lower for NH listeners. Experiment 2 evaluated the non-formant-shifting approach with additional spectral contour and high pass filtering to reduce spectral smearing and decrease distortion observed in Experiment 1. This resulted in significant intelligibility benefits of +30.2% for NH and +21.2% for CI listeners at 0 and +5 dB SNR LCN, respectively. These results suggest that LE perturbation may be useful as front-end speech modification approaches to improve intelligibility for CI users in noise.

Speech Processing to Improve the Perception of Speech in Background Noise for Children With Auditory Processing Disorder and Typically Developing Peers

Auditory processing disorder (APD) may be diagnosed when a child has listening difficulties but has normal audiometric thresholds. For adults with normal hearing and with mild-to-moderate hearing impairment, an algorithm called spectral shaping with dynamic range compression (SSDRC) has been shown to increase the intelligibility of speech when background noise is added after the processing. Here, we assessed the effect of such processing using 8 children with APD and 10 age-matched control children. The loudness of the processed and unprocessed sentences was matched using a loudness model. The task was to repeat back sentences produced by a female speaker when presented with either speech-shaped noise (SSN) or a male competing speaker (CS) at two signal-to-background ratios (SBRs). Speech identification was significantly better with SSDRC processing than without, for both groups. The benefit of SSDRC processing was greater for the SSN than for the CS background. For the SSN, scores were similar for the two groups at both SBRs. For the CS, the APD group performed significantly more poorly than the control group. The overall improvement produced by SSDRC processing could be useful for enhancing communication in a classroom where the teacher's voice is broadcast using a wireless system.