Binaural speech recognition and the Stenger effect.

The present investigation examined the effects of systematically altering the balance between speech presentation levels to the 2 ears of 12 listeners with bilateral asymmetrical sensorineural hearing impairments. Speech-recognition scores for /VCV/ speech stimuli were obtained from each participant in quiet for 9 conditions ranging from monaural poorer ear only to monaural better ear only, with 7 intermediate conditions in which the sound balance between ears was varied in 5-dB steps. High-pass spectral shaping was provided to the poorer ear, and unshaped amplification was provided to the better ear. The results suggested that, as a group, varying the sound level in the better ear within -20 to +10 dB of the centered position did not significantly change the speech recognition for these participants. No evidence of binaural interference was obtained. Findings also showed that in binaural listening situations, the Stenger effect has little influence upon speech-recognition scores. Even when the listeners were unaware of speech being presented to the better ear, their speech-recognition score reflected the better ear's abilities.     

An investigation into the effect of limiting the frequency bandwidth of speech on speech recognition in adult cochlear implant users

The purpose of this study was to investigate the effect of the limited-frequency bandwidth employed by telephones (300-3400Hz) on speech recognition in adult cochlear implant users. The Four Alternative Auditory Feature (FAAF) test was used in four conditions: unfiltered and in three filtered conditions of 300-4500Hz, 300-3400Hz and 300-2500Hz. Ten subjects implanted with the Nucleus C124M device and 10 normal-hearing listeners were assessed to examine differences between word discrimination scores in each condition. Scores obtained from the 300-3400-Hz and 300-2500-Hz filtered conditions were significantly worse than those with unfiltered speech for the cochlear implant subjects, decreasing by 17.7% and 21.4%, respectively, from scores with unfiltered speech. By contrast, the normal-hearing listeners did not experience difficulties in discriminating between words in any of the conditions. Analysis of the word errors demonstrated that the reduction in implant subject scores with bandwidth arose from errors in place of articulation. Filtering speech in this way has a significant effect on speech recognition for cochlear implant subjects but not normal-hearing listeners. Hence, the limitations of the normal telephone bandwidth can be expected to have a negative effect on speech recognition for cochlear implant users using the telephone.     

An investigation into the effect of limiting the frequency bandwidth of speech on speech recognition in adult cochlear implant users

The purpose of this study was to investigate the effect of the limited-frequency bandwidth employed by telephones (300-3400 Hz) on speech recognition in adult cochlear implant users. The Four Alternative Auditory Feature (FAAF) test was used in four conditions: unfiltered and in three filtered conditions of 300-4500 Hz, 300-3400 Hz and 300-2500 Hz. Ten subjects implanted with the Nucleus CI24M device and 10 normal-hearing listeners were assessed to examine differences between word discrimination scores in each condition. Scores obtained from the 300-3400-Hz and 300-2500-Hz filtered conditions were significantly worse than those with unfiltered speech for the cochlear implant subjects, decreasing by 17.7% and 21.4%, respectively, from scores with unfiltered speech. By contrast, the normal-hearing listeners did not experience difficulties in discriminating between words in any of the conditions. Analysis of the word errors demonstrated that the reduction in implant subject scores with bandwidth arose from errors in place of articulation. Filtering speech in this way has a significant effect on speech recognition for cochlear implant subjects but not normal-hearing listeners. Hence, the limitations of the normal telephone bandwidth can be expected to have a negative effect on speech recognition for cochlear implant users using the telephone.     

双侧人工耳蜗植入对儿童听觉识别能力影响的个案研究

目的考察双侧和单侧配戴人工耳蜗对儿童听觉识别的影响。方法本研究采用实验法和观察法。通过实验法在安静环境下使用听觉评估导航系统对幼儿的双耳和单耳进行测试。识别材料主要选择韵母识别、声母识别、单音节词声调识别、双音节词识别、短句识别。言语信号的强度为70dB SPL。通过观察法观察儿童在日常生活中双耳和单耳的表现，考察双耳与单耳在日常生活中的差异。结果实验结果表明，在声调识别和双音节词识别方面，该儿童识别率都达到100％。在韵母方面，双侧略好于单侧。在声母识别和短句识别方面，双侧人工耳蜗的语音识别率远高于单侧。在日常生活中，儿童双侧配戴人工耳蜗比单侧的言语识别率．听觉定向都要好。结论双侧人工耳蜗提高了患者的言语识别率，尤其体现在声母识别和短句识别方面。     

Quantifying the contribution of audibility to recognition of compression-amplified speech

OBJECTIVE: The speech-recognition advantages of wide-dynamic range compression (WDRC) hearing aids are believed to be a direct result of improved audibility. The main objective of this study was to compare the relationship between increasing audibility and recognition for compression-amplified versus linearly amplified speech, using a quantitative measure of audibility. A second objective was to explore the adequacy of the Aided Articulation Index (Stelmachowicz, Lewis, Kalberer, & Creutz, 1994) in describing performance with WDRC-amplified speech. DESIGN: Sixteen listeners with mild to severe sensorineural hearing loss were tested on recognition of nonsense syllables that had been digitally processed with linear or WDRC amplification. Speech recognition scores were obtained for three input levels that differed in audibility relative to the listeners' hearing thresholds. An Aided Audibility Index (AAI), ranging from 0.0 (inaudible) to 1.0 (fully audible), was calculated for each listener and condition. This importance-weighted index represents the portion of the speech signal that is available to the listener. The relationship between audibility and recognition was then examined for each type of amplification. RESULTS: At low and moderate input levels, AAI values and corresponding recognition scores were higher for the compression-amplified than for the linearly amplified speech. At high input levels, AAIs and recognition scores were essentially the same for both types of amplification. Recognition scores increased monotonically as a function of the AAI for both linear and WDRC amplifiers. There was no significant difference between the functions for linearly amplified versus compression-amplified speech. In other words, a given increase in audibility resulted in the same increase in recognition for both types of amplification. CONCLUSIONS: Increasing the amount of audible speech information plays the same role in recognition for compression-amplified as for linearly amplified speech. This suggests that, at least for the conditions tested here, compression does not introduce detrimental changes to the speech signal that offset the benefits of improved audibility. Accuracy of the compression-amplified AAI can be improved by substituting measured speech ranges for the estimated speech ranges used in the standard AAI calculation. In the absence of measured speech ranges, the standard AAI provides a close approximation.     

The use of automatic speech recognition showing the influence of nasality on speech intelligibility

Altered nasality influences speech intelligibility. Automatic speech recognition (ASR) has proved suitable for quantifying speech intelligibility in patients with different degrees of nasal emissions. We investigated the influence of hyponasality on the results of speech recognition before and after nasal surgery using ASR. Speech recordings, nasal peak inspiratory flow and self-perception measurements were carried out in 20 German-speaking patients (8 women, 12 men; aged 38 ± 22 years) who underwent surgery for various nasal and sinus pathologies. The degree of speech intelligibility was quantified as the percentage of correctly recognized words of a standardized word chain by ASR (word recognition rate; WR). WR was measured 1 day before (t1), 1 day after with nasal packings (t2), and 3 months after (t3) surgery; nasal peak flow on t1 and t3. WR was calculated with program for the automatic evaluation of all kinds of speech disorders (PEAKS). WR as a parameter of speech intelligibility was significantly decreased immediately after surgery (t1 vs. t2 p < 0.01) but increased 3 months after surgery (t2 vs. t3 p < 0.01). WR showed no association with age or gender. There was no significant difference between WR at t1 and t3, despite a post-operative increase in nasal peak inspiratory flow measurements. The results show that ASR is capable of quantifying the influence of hyponasality on speech; nasal obstruction leads to significantly reduced WR and nasal peak flow cannot replace evaluation of nasality.     

The effect of asymmetrical signal degradation on binaural speech recognition in children and adults.

To determine the effect of asymmetrical signal degradation on binaural speech recognition, 28 children and 14 adults were administered a sentence recognition task amidst multitalker babble. There were 3 listening conditions: (a) monaural, with mild degradation in 1 ear; (b) binaural, with mild degradation in both ears (symmetric degradation); and (c) binaural, with mild degradation in one ear and severe degradation in the other ear (asymmetric degradation). Sentences and babble were degraded digitally to simulate mild and severe cochlear hearing loss. All participants demonstrated significant binaural advantage (average of 7 dB) when listening to symmetrically degraded signals as compared to when listening monaurally. In contrast, adults and children achieved little or no binaural benefit, on average, when listening to asymmetrically degraded signals. Moreover, overall performance of the adults was significantly worse when listening to binaural asymmetrically degraded signals than when listening to monaural signals, thus demonstrating evidence of binaural interference. In contrast to our original speculations, however, children did not show an overall demonstration of binaural interference. Relative performance in the binaural-asymmetric and the monaural conditions was not influenced by which ear (right or left) received the more degraded signal.     

Effects of envelope expansion on speech recognition.

This study investigated the effects of expanding the gross time-amplitude variations of 'speech-envelope noise' stimuli on speech recognition. The initial stimuli were VCV logatomes presented in quiet or against a steady white noise with a 0-dB signal-to-noise ratio. Their low-frequency temporal modulations (<500 Hz) were extracted in broad frequency bands, and raised to the power 2. The resulting envelopes were then used to modulate a white noise, and combined to produce the 'speech-envelope noise' stimuli. As a consequence, listeners were forced to identify speech using primarily temporal envelope cues. The results obtained with four normal-hearing listeners show small decrements in recognition performance of 1-15% when expanding the envelope of the speech stimuli presented in quiet. The results also show a small but consistent improvement in performance of 6-14% when expanding the envelope of the speech stimuli presented in noise. These results are consistent with those obtained by Fu and Shannon (J. Acoust. Soc. Am. 104 (1998) 2570-2577) with speech presented in quiet. They also suggest that the reduction in the modulation depth of the speech envelope caused by noise or reverberation could be compensated by expanding low-frequency temporal modulations.     

Effect of frequency boundary assignment on speech recognition with the Nucleus 24 ACE speech coding strategy

The choice of frequency boundaries for the analysis channels of cochlear implants has been shown to impact the speech perception performance of adult recipients (Skinner et al, 1995; Fourakis et al, 2004). While technological limitations heretofore have limited the clinical feasibility of investigating novel frequency assignments, the SPEAR3 research processor affords the opportunity to investigate an unlimited number of possibilities. Here, four different assignments are evaluated using a variety of speech stimuli. All participants accommodated to assignment changes, and no one assignment was significantly preferred. The results suggest that better performance can be achieved using a strategy whereby (1) there are at least 7-8 electrodes allocated below 1000 Hz, (2) the majority of remaining electrodes are allocated between 1100-3000 Hz, and (3) the region above 3 kHz is represented by relatively few electrodes (i.e., 1-3). The results suggest that such frequency assignment flexibility should be made clinically available.     

Longitudinal effect of deactivating stimulation sites based on low-rate thresholds on speech recognition in cochlear implant users

Objective: The objective of the current study was to examine the longitudinal effect of deactivating stimulation sites estimated to produce broad neural excitation on speech recognition.

Design: Spatial patterns of neural excitation were estimated based on a previously established psychophysical measure, that is, detection threshold for low-rate pulse trains. Stimulation sites with relatively poor thresholds were deactivated in an experimental map. The acute effect was evaluated, in quiet and in noise, immediately after the experimental map was created (baseline), after the subjects practiced with the experimental map for two months (treatment), and after the subjects’ daily map was switched back again to the clinical map for another two months (withdrawal).

Study sample: Eight Cochlear Nucleus device users participated in the study.

Results: For both listening in noise and in quiet, the greatest effect of deactivation was observed after the subjects were given time to adapt to the new frequency allocations. The effect was comparable for listening in fluctuating and steady-state noises. All subjects benefited from deactivation for listening in noise, but subjects with greater variability in thresholds were more likely to benefit from deactivation for listening in quiet.

Conclusion: The benefit of electrode deactivation for speech recognition can increase with practice.     

Effect of two approaches to auditory training on speech recognition by hearing-impaired adults

Twenty adults with mild to moderate sensorineural hearing impairments were given three tests of speech recognition: the CUNY Nonsense Syllable Test (NST), the low predictability items of the Revised Speech Perception in Noise (RSPIN) test, and the high predictability items of the RSPIN test. They were tested on four occasions: at the beginning of the study, after one month of "no treatment," after a month of intensive auditory training, and after a further month of "no treatment." During the treatment period, 10 of the subjects spent all of the time on activities involving sentence perception and perceptual strategy while the other 10 spent half of the time on activities involving consonant recognition. A small, but statistically significant increase in speech recognition performance on the high probability material was observed in both groups subsequent to training, but the effect of training method was not significant. In addition, the gains achieved were not lost in the month following the end of training. The findings suggest that the benefits of auditory training were found in an increased use of sentence context as an aid to word recognition.     

Effects of audio-visual information on the intelligibility of alaryngeal speech

BackgroundThere is minimal research on the contribution of visual information on speech intelligibility for individuals with a laryngectomy (IWL).AimsThe purpose of this project was to determine the effects of mode of presentation (audio-only, audio-visual) on alaryngeal speech intelligibility.MethodTwenty-three naïve listeners were randomly presented 176 phonemically balanced sentences produced by three alaryngeal (tracheoesophageal, esophageal, electrolaryngeal) and one typical, laryngeal speaker in both audio-only and audio-visual modes of presentation.ResultsOverall, results showed a small (3%) but statistically significant higher speech intelligibility score for audio-visual stimuli compared to audio-only stimuli as well as a significant interaction effect between mode of speech and mode of presentation. Within mode of speech, electrolaryngeal speech was the only mode that benefited significantly from the inclusion of visual information (10% increase). Overall intelligibility showed similar patterns both within audio-only and audio-visual modes of presentation: typical laryngeal and tracheoesophageal speech modes were significantly more intelligible than both esophageal and electrolaryngeal.ConclusionsResults suggest that listeners may benefit more from visual information from speakers with poor baseline speech intelligibility. Results also show similar intelligibility between typical, laryngeal and tracheoesophageal modes of speech. Results should be interpreted with caution, however, as only one speaker from each mode of speech was included. Further research is required to determine the nature of the increase.Learning outcomes: Readers will (1) increase their understanding of the potential impact of visual information in the perception of alaryngeal speech; (2) identify potential factors that may augment or hinder speech perception; and (3) discuss how individual modes of alaryngeal speech may be affected by audio-visual information.     

Consonant enhancement effects on speech recognition of hearing-impaired children

Differences in gain (enhancement, in dB) required to optimize the consonant/vowel intensity ratio in nonsense syllables were determined for stops and fricatives, both voiced and voiceless, in 12 children with congenital moderate to severe sensorineural hearing loss. The test stimuli were vowel/consonant nonsense syllables with various levels of enhancement ranging from 0 dB (for the unprocessed stimulus) to 24 dB of gain, in steps of 3 or 6 dB. Results showed that significant improvements in consonant recognition can be obtained with individualized adjustment of consonant amplitude for children as young as 5 years of age.     

The effect of content of initial instructions on the speech discrimination scores of hearing and hearing-impaired children.

This paper investigated the effects of content of initial instructions on the speech discrimination abilities of 8 groups of children (4 groups of hearing children; 4 groups of hearing-impaired children--N = 10 children in each group). The speech discrimination abilities of the children in each group were ascertained with the AB monosyllabic word lists following two modes of initial instructions. It was concluded that with monosyllabic word lists scored phonemically it is essential to instruct each listener to repeat not meaningful whole words but also everything else that he/she recognises, including words which do not make sense, or parts of the words or even single sounds. Failure to highlight in the initial instructions the phonemic aspects of scoring brings about significantly lower speech discrimination scores.     

Across-site threshold variation in cochlear implants: relation to speech recognition

Functional implications of across-site variation in detection thresholds in subjects with cochlear implants were evaluated by comparing thresholds to speech recognition performance. Detection thresholds for bipolar (BP) and monopolar (MP) stimulation of all available stimulation sites were assessed in 21 subjects with Nucleus CI24M and CI24R(CS) implants. We found significant negative correlations between speech recognition and within-subject across-site threshold variance for both BP and MP stimulation, but no significant correlation of speech recognition with mean threshold levels. These results suggest that across-site variance of detection thresholds could provide a useful early indication of the prognosis for speech recognition and might serve as an indicator for specific therapeutic approaches in individual subjects.     

Influence of interaural level differences on the speech recognition masking level difference

This study was undertaken to determine the effect of interaural level differences on the magnitude of the speech recognition masking level differences obtained from younger and older subjects with normal hearing and from subjects with asymmetrical sensorineural hearing losses. A ten-word subgroup of CID W-1 spondaic words having the largest masking-level differences was used. Masking level differences decreased systematically with increasing interaural level differences for all three groups. At interaural level differences of 36 and 42 dB, the masking level difference persisted for the younger and older normal subjects (1.6 and 1.9 dB, respectively); similar results were obtained from the subjects with hearing losses at a 24-dB interaural level difference. For all subject groups, the S0N0 thresholds were unaffected by changes in the interaural level difference, whereas the S pi N0 thresholds were inversely related to the interaural level difference.