Intelligibility In Conditions Research Articles

Factors that can affect divided speech intelligibility

Previous studies have shown that in challenging listening situations, people find it hard to equally divide their attention between two simultaneous talkers and tend to favor one talker over the other. The aim here was to investigate whether talker onset/offset, sex and location determine the favored talker. Fifteen people with normal hearing were asked to recognize as many words as possible from two sentences uttered by two talkers located at 45° and +45° azimuth, respectively. The sentences were from the same corpus, were time-centered and had equal sound level. In Conditions 1 and 2, the talkers had different sexes (male at +45°), sentence duration was not controlled for, and sentences were presented at 65 and 35 dB SPL, respectively. Listeners favored the male over the female talker, even more so at 35 dB SPL (62 % vs 43 % word recognition, respectively) than at 65 dB SPL (74 % vs 64 %, respectively). The greater asymmetry in intelligibility at the lower level supports that divided listening is harder and more ‘asymmetric’ in challenging acoustic scenarios. Listeners continued to favor the male talker when the experiment was repeated with sentences of equal average duration for the two talkers (Condition 3). This suggests that the earlier onset or later offset of male sentences (52 ms on average) was not the reason for the asymmetric intelligibility in Conditions 1 or 2. When the location of the talkers was switched (Condition 4) or the two talkers were the same woman (Condition 5), listeners continued to favor the talker to their right albeit non-significantly. Altogether, results confirm that in hard divided listening situations, listeners tend to favor the talker to their right. This preference is not affected by talker onset/offset delays less than 52 ms on average. Instead, the preference seems to be modulated by the voice characteristics of the talkers.

Refinement and validation of the binaural short time objective intelligibility measure for spatially diverse conditions

Speech intelligibility prediction methods have recently gained popularity in the speech processing community as supplements to time consuming and costly listening experiments. Such methods can be used to objectively quantify and compare the advantage of different speech enhancement algorithms, in a way that correlates well with actual speech intelligibility. One such method is the short-time objective intelligibility (STOI) measure. In a recent publication, we proposed a binaural version of the STOI measure, based on a modified version of the equalization cancellation (EC) model. This measure was shown to retain many of the advantageous properties of the STOI measure, while at the same time being able to predict intelligibility correctly in conditions involving both binaural advantage and non-linear signal processing. The biggest prediction errors were found for conditions involving multiple spatially distributed interferers. In this paper, we report results for a new listening experiment including different mixtures of isotropic and point source noise. This exposes that the binaural STOI measure has a tendency to overestimate the intelligibility in conditions with spatially distributed interferes at low signal to noise ratios (SNRs). This condition-dependent error can make it difficult to compare intelligibility across different acoustical conditions. We investigate the cause of this upward bias, and propose a correction which alleviates the problem. The modified method is evaluated with five datasets of measured intelligibility, spanning a wide range of realistic acoustic conditions. Within the tested conditions, the modified method yields very accurate predictions, and entirely alleviates the aforementioned tendency to overestimate intelligibility in conditions with spatially distributed interferers.

Rehabilitation of patients after ear surgery: prospects of auditory and vestibular training in non­invasive neuromodulation

The objective of the research is to evaluate the efficacy of rehabilitation in 73 patients with hearing and vestibulation impairment after ear surgery. Rehabilitation had the form of a set of auditory and vestibular training in conditions of non­invasive neuromodulation. Vestibular training had the form of an exercise on equilibrium control with the eyes closed performed with the help of Brain Port device during a week after surgery. Audial training was a 10-days acoustic stimulation on the expiry of 1 month after surgery. In both cases non­invasive neuromodulation was provided by electrotactile stimulation of tongue using Brain Port device. The data of tone threshold audiometry, speech intelligibility in conditions of speech interference, computerized posturography and gate examination were evaluated. The results confirm effectiveness of the used rehabilitation activities for speech intelligibility and gait improvement in majority of the patients.

The role of high-frequency envelope fluctuations for speech masking release

The speech-based envelope power spectrum model (sEPSM; Jo/rgensen and Dau, 2011; Jo/rgensen et al., 2013) was shown to successfully predict speech intelligibility in conditions with stationary and fluctuating interferers, reverberation, and spectral subtraction. The key element in the model was the multi-resolution estimation of the signal-to-noise ratio in the envelope domain (SNRenv) at the output of a modulation filterbank. The simulations suggested that mainly modulation filters centered in the range from 1-8 Hz contribute to speech intelligibility in the case of stationary maskers whereas modulation filters tuned to frequencies above 16 Hz might be important in the case of fluctuating maskers. In the present study, the role of high-frequency envelope fluctuations for speech masking release was further investigated in conditions of speech-on-speech Simulations were compared to various measured data from normal-hearing listeners (Festen and Plomp, 1990; Christiansen et al., 2013). The results support the hypothesis that high-frequency envelope fluctuations (>30 Hz) are essential for speech intelligibility in conditions with speech interferers. While the sEPSM reflects effects of energetic and modulation masking in speech intelligibility, the remaining unexplored effect in some conditions may be attributed to, and defined as, informational masking.

Speech intelligibility in real and virtual adverse auditory environments

The purpose of this investigation was to examine the effects of real and virtual adverse conditions on speech intelligibility. The experiment was designed to examine the effect of presentation method on speech intelligibility in conditions of noise and reverberation as signal-to-noise ratio was systematically varied. Additionally, this investigation evaluated the influence of talker gender on speech intelligibility in anechoic and reverberant environments as a function of signal-to-noise ratio and presentation method. Speech intelligibility scores were obtained from 21 normal hearing subjects using a nonsense syllable test. The syllables were recorded in three environments (diotic anechoic, virtual anechoic, and virtual reverberant) with three signal-to-noise ratios (0, 5, 9 dB) using two simultaneous masking sources. The findings indicate that (a) traditional diotic presentation of these stimuli degrades speech intelligibility compared to virtual presentation and may not accurately represent real-world performance; (b) the signal-to-noise ratios did not influence performance trends between presentation modes, as intelligibility improved with increasing SNR; (c) reverberation decreased intelligibility although the effects were not as dramatic as expected; and (d) using these stimuli, the female talker tokens were more easily identified than male talkers in a virtual presentation, but not generally for diotic presentation. [Work supported by NICDC and U.S. Army.]