Effect of audibility on spatial release from speech-on-speech masking

This study investigated to what extent spatial release from masking (SRM) deficits in hearing-impaired adults may be related to reduced audibility of the test stimuli. Sixteen adults with sensorineural hearing loss and 28 adults with normal hearing were assessed on the Listening in Spatialized Noise–Sentences test, which measures SRM using a symmetric speech-on-speech masking task. Stimuli for the hearing-impaired listeners were delivered using three amplification levels (National Acoustic Laboratories - Revised Profound prescription (NAL-RP) +25%, and NAL-RP +50%), while stimuli for the normal-hearing group were filtered to achieve matched audibility. SRM increased as audibility increased for all participants. Thus, it is concluded that reduced audibility of stimuli may be a significant factor in hearing-impaired adults' reduced SRM even when hearing loss is compensated for with linear gain. However, the SRM achieved by the normal hearers with simulated audibility loss was still significantly greater than that achieved by hearing-impaired listeners, suggesting other factors besides audibility may still play a role

Speech intelligibility for target and masker with different spectra

The speech intelligibility index (SII) calculation is based on the assumption that the effective range of signal-to-noise ratio (SNR) regarding speech intelligibility is [− 15 dB; +15 dB]. In a specific frequency band, speech intelligibility would remain constant by varying the SNRs above + 15 dB or below − 15 dB. These assumptions were tested in four experiments measuring speech reception thresholds (SRTs) with a speech target and speech-spectrum noise, while attenuating target or noise above or below 1400 Hz, with different levels of attenuation in order to test different SNRs in the two bands. SRT varied linearly with attenuation at low-attenuation levels and an asymptote was reached for high-attenuation levels. However, this asymptote was reached (intelligibility was not influenced by further attenuation) for different attenuation levels across experiments. The − 15-dB SII limit was confirmed for high-pass filtered targets, whereas for low-pass filtered targets, intelligibility was further impaired by decreasing the SNR below − 15 dB (until − 37 dB) in the high-frequency band. For high-pass and low-pass filtered noises, speech intelligibility kept improving when increasing the SNR in the rejected band beyond + 15 dB (up to 43 dB). Before reaching the asymptote, a 10-dB increase of SNR obtained by filtering the noise resulted in a larger decrease of SRT than a corresponding 10-dB decrease of SNR obtained by filtering the target (the slopes SRT/attenuation were different depending on which source was filtered). These results question the use of the SNR range and the importance function adopted by the SII when considering sharply filtered signals

The listening talker: A review of human and algorithmic context-induced modifications of speech

International audienceSpeech output technology is finding widespread application, including in scenarios where intelligibility might be compromised - at least for some listeners - by adverse conditions. Unlike most current algorithms, talkers continually adapt their speech patterns as a response to the immediate context of spoken communication, where the type of interlocutor and the environment are the dominant situational factors influencing speech production. Observations of talker behaviour can motivate the design of more robust speech output algorithms. Starting with a listener-oriented categorisation of possible goals for speech modification, this review article summarises the extensive set of behavioural findings related to human speech modification, identifies which factors appear to be beneficial, and goes on to examine previous computational attempts to improve intelligibility in noise. The review concludes by tabulating 46 speech modifications, many of which have yet to be perceptually or algorithmically evaluated. Consequently, the review provides a roadmap for future work in improving the robustness of speech output

Predicting the effects of periodicity on the intelligibility of masked speech:An evaluation of different modelling approaches and their limitations

Four existing speech intelligibility models with different theoretical assumptions were used to predict previously published behavioural data. Those data showed that complex tones with pitch-related periodicity are far less effective maskers of speech than aperiodic noise. This so-called masker-periodicity benefit (MPB) far exceeded the fluctuating-masker benefit (FMB) obtained from slow masker envelope fluctuations. In contrast, the normal-hearing listeners hardly benefitted from periodicity in the target speech. All tested models consistently underestimated MPB and FMB, while most of them also overestimated the intelligibility of vocoded speech. To understand these shortcomings, the internal signal representations of the models were analysed in detail. The best-performing model, the correlation-based version of the speech-based envelope power spectrum model (sEPSMcorr), combined an auditory processing front end with a modulation filterbank and a correlation-based back end. This model was then modified to further improve the predictions. The resulting second version of the sEPSMcorr outperformed the original model with all tested maskers and accounted for about half the MPB, which can be attributed to reduced modulation masking caused by the periodic maskers. However, as the sEPSMcorr2 failed to account for the other half of the MPB, the results also indicate that future models should consider the contribution of pitch-related effects, such as enhanced stream segregation, to further improve their predictive power