Spatial release from masking in the median plane with non-native speakers using individual and mannequin head related transfer functions.

Spatial release from masking (SRM) in speech-on-speech tasks has been widely studied in the horizontal plane, where interaural cues play a fundamental role. Several studies have also observed SRM for sources located in the median plane, where (monaural) spectral cues are more important. However, a relatively unexplored research question concerns the impact of head-related transfer function (HRTF) personalisation on SRM, for example, whether using individually-measured HRTFs results in better performance if compared with the use of mannequin HRTFs. This study compares SRM in the median plane in a speech-on-speech virtual task rendered using both individual and mannequin HRTFs. SRM is obtained using English sentences with non-native English speakers. Our participants show lower SRM performances compared to those found by others using native English participants. Furthermore, SRM is significantly larger when the source is spatialised using the individual HRTF, and this effect is more marked for those with lower English proficiency. Further analyses using a spectral distortion metric and the estimation of the better-ear effect, show that the observed SRM can only partially be explained by HRTF-specific factors and that the effect of the familiarity with individual spatial cues is likely to be the most significant element driving these results.

Modelling binaural unmasking and the intelligibility of speech in noise and reverberation for normal-hearing and hearing-impaired listeners.

This study investigated the effect of hearing loss on binaural unmasking (BU) for the intelligibility of speech in noise. Speech reception thresholds (SRTs) were measured with normal-hearing (NH) listeners and older mildly hearing-impaired (HI) listeners while varying the presentation level of the stimuli, reverberation, modulation of the noise masker, and spatial separation of the speech and noise sources. On average across conditions, the NH listeners benefited more (by 0.6 dB) from BU than HI listeners. The binaural intelligibility model developed by Vicente, Lavandier, and Buchholz [J. Acoust. Soc. Am. 148, 3305-3317 (2020)] was used to describe the data, accurate predictions were obtained for the conditions considering moderate noise levels [50 and 60 dB sound pressure level (SPL)]. The interaural jitters that were involved in the prediction of BU had to be revised to describe the data measured at a lower level (40 dB SPL). Across all tested conditions, the correlation between the measured and predicted SRTs was 0.92, whereas the mean prediction error was 0.9 dB.

A binaural model implementing an internal noise to predict the effect of hearing impairment on speech intelligibility in non-stationary noises.

A binaural model predicting speech intelligibility in envelope-modulated noise for normal-hearing (NH) and hearing-impaired listeners is proposed. The study shows the importance of considering an internal noise with two components relying on the individual audiogram and the level of the external stimuli. The model was optimized and verified using speech reception thresholds previously measured in three experiments involving NH and hearing-impaired listeners and sharing common methods. The anechoic target, in front of the listener, was presented simultaneously through headphones with two anechoic noise-vocoded speech maskers (VSs) either co-located with the target or spatially separated using an infinite broadband interaural level difference without crosstalk between ears. In experiment 1, two stationary noise maskers were also tested. In experiment 2, the VSs were presented at different sensation levels to vary audibility. In experiment 3, the effects of realistic interaural time and level differences were also tested. The model was applied to two datasets involving NH listeners to verify its backward compatibility. It was optimized to predict the data, leading to a correlation and mean absolute error between data and predictions above 0.93 and below 1.1 dB, respectively. The different internal noise approaches proposed in the literature to describe hearing impairment are discussed.

Further validation of a binaural model predicting speech intelligibility against envelope-modulated noises.

Collin and Lavandier [J. Acoust. Soc. Am. 134, 1146-1159 (2013)] proposed a binaural model predicting speech intelligibility against envelope-modulated noises, evaluated in 24 acoustic conditions, involving similar masker types. The aim of the present study was to test the model robustness modeling 80 additional conditions, and evaluate the influence of its parameters using an approach inspired by a variance-based sensitivity analysis. First, the data from four experiments from the literature and one specifically designed for the present study were used to evaluate the prediction performance of the model, investigate potential interactions between its parameters, and define their values leading to the best predictions. A revision of the model allowed to account for binaural sluggishness. Finally, the optimized model was tested on an additional dataset not used to define its parameters. Overall, one hundred conditions split into six experiments were modeled. Correlation between data and predictions ranged from 0.85 to 0.96 across experiments, and mean absolute prediction errors were between 0.5 and 1.4 dB.