Effectiveness of computer-based auditory training in improving the perception of noise-vocoded speech

Five experiments were designed to evaluate the effectiveness of “high-variability” lexical training in improving the ability of normal-hearing subjects to perceive noise-vocoded speech that had been spectrally shifted to simulate tonotopic misalignment. Two approaches to training were implemented. One training approach required subjects to recognize isolated words, while the other training approach required subjects to recognize words in sentences. Both approaches to training improved the ability to identify words in sentences. Improvements following a single session (lasting 1–2 h) of auditory training ranged between 7 and 12 %pts and were significantly larger than improvements following a visual control task that was matched with the auditory training task in terms of the response demands. An additional three sessions of word- and sentence-based training led to further improvements, with the average overall improvement ranging from 13 to 18 %pts. When a tonotopic misalignment of 3 mm rather than 6 mm was simulated, training with several talkers led to greater generalization to new talkers than training with a single talker. The results confirm that computer-based lexical training can help overcome the effects of spectral distortions in speech, and they suggest that training materials are most effective when several talkers are included

Peripheral hearing loss reduces the ability of children to direct selective attention during multi-talker listening

Restoring normal hearing requires knowledge of how peripheral and central auditory processes are affected by hearing loss. Previous research has focussed primarily on peripheral changes following sensorineural hearing loss, whereas consequences for central auditory processing have received less attention. We examined the ability of hearing-impaired children to direct auditory attention to a voice of interest (based on the talker’s spatial location or gender) in the presence of a common form of background noise: the voices of competing talkers (i.e. during multi-talker, or “Cocktail Party” listening). We measured brain activity using electro-encephalography (EEG) when children prepared to direct attention to the spatial location or gender of an upcoming target talker who spoke in a mixture of three talkers. Compared to normally-hearing children, hearing-impaired children showed significantly less evidence of preparatory brain activity when required to direct spatial attention. This finding is consistent with the idea that hearing-impaired children have a reduced ability to prepare spatial attention for an upcoming talker. Moreover, preparatory brain activity was not restored when hearing-impaired children listened with their acoustic hearing aids. An implication of these findings is that steps to improve auditory attention alongside acoustic hearing aids may be required to improve the ability of hearing-impaired children to understand speech in the presence of competing talkers

Presentation modality influences behavioral measures of alerting, orienting, and executive control

The Attention Network Test (ANT) uses visual stimuli to separately assess the attentional skills of alerting (improved performance following a warning cue), spatial orienting (an additional benefit when the warning cue also cues target location), and executive control (impaired performance when a target stimulus contains conflicting information). This study contrasted performance on auditory and visual versions of the ANT to determine whether the measures it obtains are influenced by presentation modality. Forty healthy volunteers completed both auditory and visual tests. Reaction-time measures of executive control were of a similar magnitude and significantly correlated, suggesting that executive control might be a supramodal resource. Measures of alerting were also comparable across tasks. In contrast, spatial-orienting benefits were obtained only in the visual task. Auditory spatial cues did not improve response times to auditory targets presented at the cued location. The different spatial-orienting measures could reflect either separate orienting resources for each perceptual modality, or an interaction between a supramodal orienting resource and modality-specific perceptual processing

Development and Critical Evaluation of a Condition-Specific Preference-Based Measure Sensitive to Binaural Hearing in Adults: The York Binaural Hearing–Related Quality-of-Life System

Objectives: The widely-used generic preference-based measures of health-related quality of life—the EuroQol Descriptive System (EQ-5D) and the Health Utilities Index (HUI3)—are limited in their response to technologies that improve hearing. The EQ-5D lacks construct validity for hearing, while the HUI3 is restricted by a ceiling effect and by using speech reception as the only evidence of the ability to hear. Consequently, neither measure consistently registers benefits from binaural hearing, such as those from bilateral versus unilateral cochlear implantation. The objectives were to test whether informants value binaural hearing, to develop a condition-specific preference-based measure sensitive to binaural hearing, to assess the psychometric properties of the new instrument, and to determine whether it meets requirements for informing judgments of cost-effectiveness: does it measure greater gains than do the generic preference-based measures, while avoiding exaggerating losses, and displaying sensitivity to side effects?Design: Three levels of function, ranging from no difficulty to great difficulty, were defined on each of three dimensions where listening is easier or more successful when hearing is binaural rather than monaural: perception of speech in spatially separated noise, localization of sounds, and effort and fatigue. Informants (N = 203) valued the 27 combinations of levels and dimensions in a time trade-off task with a 10-year time frame to provide a value of binaural-related quality of life (“binaural utility”) for each combination. A questionnaire was compiled to allow respondents to report their level of function on each dimension so that a value of binaural utility could be assigned to them. The questionnaire and the age-standardized valuations constitute The York Binaural Hearing–Related Quality-of-Life System (YBHRQL). Adult users of unilateral implants (N = 8), bilateral implants (N = 11), or bimodal aiding (N = 9) undertook performance tests of spatial listening and completed the HUI3, EQ-5D, and Speech, Spatial, and Qualities of Hearing (SSQ) questionnaires. They completed the YBHRQL questionnaire 24 and 38 mo later.Results: Despite long intervals between measurements, the YBHRQL demonstrated desirable psychometric properties: good construct validity evidenced by significant correlations with performance measures and the SSQ index; a greater ability than the EQ-5D or HUI3 to distinguish unilateral, bimodal, and bilateral listening; and good reproducibility. The YBHRQL did not exaggerate losses of utility but was insensitive to a potential side effect of implantation (pain/discomfort). It measured a gain in utility from bilateral compared with unilateral implantation (median = 0.11, interquartile range, 0.03 to 0.16) that was greater than the gain measured by the EQ-5D (0.00, 0.00 to 0.00) but not the HUI3 (0.00, 0.00 to 0.17).Conclusions: The YBHRQL summarizes the contribution of binaural hearing to quality of life by combining the functional status of a listener with the preferences of independent informants. It would be an efficient clinical outcome measure. In addition, if used alongside the EQ-5D or HUI3, it would provide evidence which could beneficially modulate confidence in the cost-effectiveness of interventions. Further research on its sensitivity to side effects, and on the size of the gains in utility which it measures, is needed to determine whether it could stand alone to inform resource-allocation decisions

Benefit of temporal fine structure to speech perception in noise measured with controlled temporal envelopes

Previous studies have assessed the importance of temporal fine structure (TFS) for speech perception in noise by comparing the performance of normal-hearing listeners in two conditions. In one condition, the stimuli have useful information in both their temporal envelopes and their TFS. In the other condition, stimuli are vocoded and contain useful information only in their temporal envelopes. However, these studies have confounded differences in TFS with differences in the temporal envelope. The present study manipulated the analytic signal of stimuli to preserve the temporal envelope between conditions with different TFS. The inclusion of informative TFS improved speech reception thresholds for sentences presented in steady and modulated noise, demonstrating that there are significant benefits of including informative TFS even when the temporal envelope is controlled. It is likely that the results of previous studies largely reflect the benefits of TFS, rather than uncontrolled effects of changes in the temporal envelope

Physiological Evidence for a Midline Spatial Channel in Human Auditory Cortex

Studies with humans and other mammals have provided support for a two-channel representation of horizontal (“azimuthal”) space in the auditory system. In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location. One channel is maximally responsive to sounds towards the left and the other to sounds towards the right. However, recent psychophysical studies of humans, and physiological studies of other mammals, point to the presence of an additional channel, maximally responsive to the midline. In this study, we used electroencephalography to seek physiological evidence for such a midline channel in humans. We measured neural responses to probe stimuli presented from straight ahead (0 °) or towards the right (+30 ° or +90 °). Probes were preceded by adapter stimuli to temporarily suppress channel activity. Adapters came from 0 ° or alternated between left and right (−30 ° and +30 ° or −90 ° and +90 °). For the +90 ° probe, to which the right-tuned channel would respond most strongly, both accounts predict greatest adaptation when the adapters are at ±90 °. For the 0 ° probe, the two-channel account predicts greatest adaptation from the ±90 ° adapters, while the three-channel account predicts greatest adaptation when the adapters are at 0 ° because these adapters stimulate the midline-tuned channel which responds most strongly to the 0 ° probe. The results were consistent with the three-channel account. In addition, a computational implementation of the three-channel account fitted the probe response sizes well, explaining 93 % of the variance about the mean, whereas a two-channel implementation produced a poor fit and explained only 61 % of the variance

EEG activity evoked in preparation for multi-talker listening by adults and children

Selective attention is critical for successful speech perception because speech is often encountered in the presence of other sounds, including the voices of competing talkers. Faced with the need to attend selectively, listeners perceive speech more accurately when they know characteristics of upcoming talkers before they begin to speak. However, the neural processes that underlie the preparation of selective attention for voices are not fully understood. The current experiments used electroencephalography (EEG) to investigate the time course of brain activity during preparation for an upcoming talker in young adults aged 18-27 years with normal hearing (Experiments 1 and 2) and in typically-developing children aged 7-13 years (Experiment 3). Participants reported key words spoken by a target talker when an opposite-gender distractor talker spoke simultaneously. The two talkers were presented from different spatial locations (±30° azimuth). Before the talkers began to speak, a visual cue indicated either the location (left/right) or the gender (male/female) of the target talker. Adults evoked preparatory EEG activity that started shortly after

Benefit of temporal fine structure to speech perception in noise measured with controlled temporal envelopes

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America. This article appeared in EAVES, J.M., SUMMERFIELD, A.Q. and KITTERICK, P.T., 2011. Benefit of temporal fine structure to speech perception in noise measured with controlled temporal envelopes. Journal of the Acoustical Society of America, 130(1), pp. 501-507. and may be found at http://dx.doi.org/10.1121/1.3592237Previous studies have assessed the importance of temporal fine structure (TFS) for speech perception in noise by comparing the performance of normal-hearing listeners in two conditions. In one condition, the stimuli have useful information in both their temporal envelopes and their TFS. In the other condition, stimuli are vocoded and contain useful information only in their temporal envelopes. However, these studies have confounded differences in TFS with differences in the temporal envelope. The present study manipulated the analytic signal of stimuli to preserve the temporal envelope between conditions with different TFS. The inclusion of informative TFS improved speech reception thresholds for sentences presented in steady and modulated noise, demonstrating that there are significant benefits of including informative TFS even when the temporal envelope is controlled. It is likely that the results of previous studies largely reflect the benefits of TFS, rather than uncontrolled effects of changes in the temporal envelope