Speech Recognition In Background Noise Research Articles

Speech-in-Noise and Dichotic Auditory Training Students With Autism Spectrum Disorder.

Individuals diagnosed with autism spectrum disorder (ASD) often exhibit auditory processing issues, including poor speech recognition in background noise and dichotic processing (integration of different stimuli presented to the two ears). Auditory training could mitigate these auditory difficulties. However, few auditory training programs have been designed to target specific listening deficits for students with ASD. The present study summarizes the development of an innovative, one-on-one, clinician-developed speech-in-noise (SIN) training program that has not been previously described and an existing dichotic auditory training program to address common auditory processing deficits in students with ASD. Twenty verbal students with ASD, ages 7-17 years, completed a one-on-one, clinician-developed SIN training program and a commercially available dichotic training program 2-3 times a week (30-45 min per session) for 12 weeks. Maximum and minimum training levels from the SIN and dichotic training programs were analyzed statistically to document changes in training level over the training period. Analyses of the pre- and posttraining data revealed significant improvements in training level for both the SIN and dichotic training programs. Overall, the proposed SIN training resulted in significant improvements in training level and may be used along with dichotic training to improve some of the most common auditory processing issues documented in verbal individuals with ASD requiring minimal support. Both types of auditory training may be implemented in one-on-one therapy in clinics and in the schools.

Difficulties Experienced by Older Listeners in Utilizing Voice Cues for Speaker Discrimination.

Human listeners are assumed to apply different strategies to improve speech recognition in background noise. Young listeners with normal hearing (NH), e.g., have been shown to follow the voice of a particular speaker based on the fundamental (F0) and formant frequencies, which are both influenced by the gender, age, and size of the speaker. However, the auditory and cognitive processes that underlie the extraction and discrimination of these voice cues across speakers may be subject to age-related decline. The present study aimed to examine the utilization of F0 and formant cues for voice discrimination (VD) in older adults with hearing expected for their age. Difference limens (DLs) for VD were estimated in 15 healthy older adults (65–78 years old) and 35 young adults (18–35 years old) using only F0 cues, only formant frequency cues, and a combination of F0 + formant frequencies. A three-alternative forced-choice paradigm with an adaptive-tracking threshold-seeking procedure was used. Wechsler backward digit span test was used as a measure of auditory working memory. Trail Making Test (TMT) was used to provide cognitive information reflecting a combined effect of processing speed, mental flexibility, and executive control abilities. The results showed that (a) the mean VD thresholds of the older adults were poorer than those of the young adults for all voice cues, although larger variability was observed among the older listeners; (b) both age groups found the formant cues more beneficial for VD, compared to the F0 cues, and the combined (F0 + formant) cues resulted in better thresholds, compared to each cue separately; (c) significant associations were found for the older adults in the combined F0 + formant condition between VD and TMT scores, and between VD and hearing sensitivity, supporting the notion that a decline with age in both top-down and bottom-up mechanisms may hamper the ability of older adults to discriminate between voices. The present findings suggest that older listeners may have difficulty following the voice of a specific speaker and thus implementing doing so as a strategy for listening amid noise. This may contribute to understanding their reported difficulty listening in adverse conditions.

PET/CT background noise and its effect on speech recognition

Positron emission tomography (PET) has been successfully used to investigate central nervous processes, including the central auditory pathway. Unlike early water-cooled PET-scanners, novel PET/CT scanners employ air cooling and include a CT system, both of which result in higher background noise levels. In the present study, we describe the background noise generated by two state-of-the-art air-cooled PET/CT scanners. We measured speech recognition in background noise: recorded PET noise and a speech-shaped noise applied in clinical routine to subjects with normal hearing. Background noise produced by air-cooled PET/CT is considerable: 75.1 dB SPL (64.5 dB(A)) for the Philips Gemini TF64 and 76.9 dB SPL (68.4 dB(A)) for the Philips Vereos PET/CT (Philips Healthcare, The Netherlands). Subjects with normal hearing exhibited better speech recognition in recorded PET background noise compared with clinically applied speech-shaped noise. Speech recognition in both background noises correlated significantly. Background noise generated by PET/CT scanners should be considered when PET is used for the investigation of the central auditory pathway. Speech in PET noise is better than in speech-shaped noise because of the minor masking effect of the background noise of the PET/CT.

Prediction of speech recognition in background noise and competing speech from suprathreshold auditory and cognitive measures

Previous studies have struggled to identify measures beyond the audiogram to reliably predict speech-in-noise scores. This may owe to: (i) different mechanisms mediate performance depending on materials and task; and (ii) effects are not reproducible. Here, 38 listeners with normal/near-normal audiograms completed batteries of temporal auditory and cognitive tests, and speech recognition (“Theo-Victor-Michael” test) in speech-shaped noise (SSN), speech-envelope modulated noise (envSSN), one (1T) and two (2T) competing talkers. A two-stage Bayesian modeling approach was employed. In Stage 1, speech scores were corrected for target-word frequency/neighborhood density, psychometric function parameters were extracted from temporal tests, and cognitive measures were reduced to three composite variables. Stage 2 then applied Gaussian process models to predict speech scores from temporal and cognitive measures. Leave-one-out cross-validation and model stacking determined the best combination of predictive models. Performance in SSN/envSSN was best predicted by temporal envelope measures (forward masking, gap duration discrimination), while performance in 1T was best predicted by cognitive measures (executive function, processing speed). Temporal fine structure measures (frequency-modulation, interaural-phase-difference detection) predicted the number of 1T distractor responses. All models failed on 2T. These results show that prediction of speech-in-noise scores from suprathreshold “process” measures is highly task dependent.

Effects of word frequency and phonological neighborhood density on speech recognition in background noise and competing speech

Clinical speech-in-noise tests typically use materials without contextual constraint or balanced for linguistic properties like word/phoneme frequency. However, real-world linguistic context effects can be substantial and vary by listener and scenario. Here, 38 participants completed the Theo-Victor-Michael (TVM) speech test in four types of background: speech shaped noise (SSN), speech-envelope modulated noise (envSSN), one competing talker (1T), and two competing talkers (2T) (Helfer and Freyman, 2009). The TVM is a matrix test using keywords from a corpus of one- and two- syllable nouns that vary considerably in word frequency (FREQ) and phonological neighborhood density (DENS). Bayesian logistic regression was used to estimate the effects of FREQ/DENS on TVM performance. A multinomial model was used for 1T/2T to assess reporting of target and distractor keywords. Overall, percent-correct recognition increased with increasing keyword FREQ and decreased with increasing keyword DENS. Effects were larger in SSN/envSSN than 1T/2T. Statistically significant but small effects of FREQ/DENS were observed on distractor responses in 1T/2T. Adjusting performance for FREQ/DENS substantially shifted the distribution of scores but only for SSN/envSSN. Performance in 1T/2T may be dominated by non-linguistic factors, and/or less sensitive to FREQ/DENS due to higher difficulty or linguistic competition from the background talkers. [Work supported by VA RR&D Service.]

Speech Recognition in Noise in Single-Sided Deaf Cochlear Implant Children on Using Adaptive Digital Microphone Technology.

Previous research demonstrated benefits of adaptive digital microphone technologies (ADMTs) in adults with single-sided deafness (SSD) having a cochlear implant (CI). Children with SSD are especially affected by background noise because of their noise exposure in kindergarten and school. This article aims to evaluate possible effects of ADMT on speech recognition in background noise in children with SSD who use a CI. Ten children between 5 and 11 years of age were included. Speech recognition in noise was assessed for one frontal distant and two lateral speakers. The speech stimulus was presented at a speech level of 65 dB(A) and noise at a level of 55 dB(A). For the presentation condition with one frontal speaker, four listening conditions were assessed: (1) normal-hearing (NH) ear and CI turned off; (2) NH ear and CI; (3) NH ear and CI with ADMT; and (4) NH ear with ADMT and CI. Listening conditions (2) to (4) were also tested for each lateral speaker. The frontal speaker was positioned directly in front of the participant, whereas the lateral speakers were positioned at angles of 90 degrees and -90 degrees to the participant's head. Children with SSD who use a CI significantly benefit from the application of ADMT in speech recognition in noise for frontal distant and for lateral speakers. Speech recognition improved significantly with ADMT at the CI and the NH ears. Application of ADMT significantly improves speech recognition in noise in children with SSD who use a CI and can therefore be highly recommended. The decision of whether to apply ADMT at the CI NH ear or bilaterally should be made for each child individually.

Is the cochlear implant a successful long-term solution for single-sided deaf and asymmetric hearing-impaired patients?

PurposeWe investigated the long-term results of cochlear implant (CI) recipients with asymmetric hearing loss (AHL) or single-sided deafness (SSD). We focused on wearing behavior, audiometric hearing rehabilitation, and subjective benefits of the CI. CI is expected to improve audiological results, subjective hearing perception, and tinnitus burden.MethodsSpeech recognition in background noise and sound localization were assessed preoperatively and after at least six years of CI experience. Validated questionnaires determined the subjective benefit of CI use and the subjective evaluation of tinnitus.ResultsOver 80% of the included AHL and SSD CI recipients used their CI between 6 and 10 h daily; four subjects with SSD were non-users. Speech recognition in background noise and sound localization improved significantly compared with the unaided preoperative situation. Additionally, CI improved subjective speech intelligibility and spatial hearing impression while reducing tinnitus burden.ConclusionSubjects with AHL and SSD benefit from CI, subjectively and audiologically. Cochlear implant is a successful long-term treatment for AHL and SSD.

Contribution of noise reduction pre-processing and microphone directionality strategies in the speech recognition in noise in adult cochlear implant users.

Refinement currently offered in new sound processors may improve noise listening capability reducing constant background noise and enhancing listening in challenging signal-to-noise conditions. This study aimed to identify whether the new version of speech processor preprocessing strategy contributes to speech recognition in background noise compared to the previous generation processor. This was a multicentric prospective cross-sectional study. Post-lingually deaf adult patients, with at least 1year of device use and speech recognition scores above 60% on HINT sentences in quiet were invited. Speech recognition performance in quiet and in noise with sound processors with previous and recent technologies was assessed under four conditions with speech coming from the front: (a) quiet (b) fixed noise coming from the front, (c) fixed noise coming from the back, and (d) adaptive noise ratios with noise coming from the front. Forty-seven cochlear implant users were included. No significant difference was found in quiet condition. Performance with the new processor was statistically better than the previous sound processor in all three noisy conditions (p < 0.05). With fixed noise coming from the back condition, speech recognition was 62.9% with the previous technology and 73.5% on the new one (p < 0.05). The mean speech recognition in noise was also statistically higher, with 5.8dB and 7.1dB for the newer and older technologies (p < 0.05), respectively. New technology has shown to provide benefits regarding speech recognition in noise. In addition, the new background noise reduction technology, has shown to be effective and improves speech recognition in situations of more intense noise coming from behind.

Effect of Microphone Location and Beamforming Technology on Speech Recognition in Pediatric Cochlear Implant Recipients.

Despite improvements in cochlear implant (CI) technology, pediatric CI recipients continue to have more difficulty understanding speech than their typically hearing peers in background noise. A variety of strategies have been evaluated to help mitigate this disparity, such as signal processing, remote microphone technology, and microphone placement. Previous studies regarding microphone placement used speech processors that are now dated, and most studies investigating the improvement of speech recognition in background noise included adult listeners only. The purpose of the present study was to investigate the effects of microphone location and beamforming technology on speech understanding for pediatric CI recipients in noise. A prospective, repeated-measures, within-participant design was used to compare performance across listening conditions. A total of nine children (aged 6.6 to 15.3 years) with at least one Advanced Bionics CI were recruited for this study. The Basic English Lexicon Sentences and AzBio Sentences were presented at 0o azimuth at 65-dB SPL in +5 signal-to-noise ratio noise presented from seven speakers using the R-SPACE system (Advanced Bionics, Valencia, CA). Performance was compared across three omnidirectional microphone configurations (processor microphone, T-Mic 2, and processor + T-Mic 2) and two directional microphone configurations (UltraZoom and auto UltraZoom). The two youngest participants were not tested in the directional microphone configurations. No significant differences were found between the various omnidirectional microphone configurations. UltraZoom provided significant benefit over all omnidirectional microphone configurations (T-Mic 2, p = 0.004, processor microphone, p < 0.001, and processor microphone + T-Mic 2, p = 0.018) but was not significantly different from auto UltraZoom (p = 0.176). All omnidirectional microphone configurations yielded similar performance, suggesting that a child's listening performance in noise will not be compromised by choosing the microphone configuration best suited for the child. UltraZoom (adaptive beamformer) yielded higher performance than all omnidirectional microphones in moderate background noise for adolescents aged 9 to 15 years. The implications of these data suggest that for older children who are able to reliably use manual controls, UltraZoom will yield significantly higher performance in background noise when the target is in front of the listener.

Towards optogenetic approaches for hearing restoration

Hearing impairment (HI) is the most frequent sensory deficit in humans. As yet there is no causal therapy for sensorineural HI - the most common form – that results from cochlear dysfunction. Hearing aids and electrical cochlear implants (eCIs) remain the key options for hearing rehabilitation. The eCI, used by more than 0.7 Mio people with profound HI or deafness, is considered the most successful neuroprosthesis as it typically enables open speech comprehension in quiet. By electrically stimulating the auditory nerve, eCIs constitute a brain-machine interface re-connecting the patient with the auditory scene. Nonetheless, there are short-comings resulting from the wide spread of electric current inside the cochlea which limit the quality of artificial hearing. Since light can be better confined in space than electric current, optogenetic stimulation of the auditory nerve has been suggested as an alternative approach for hearing restoration, enabling higher resolution of artificial sound encoding. Future optical CIs (oCIS) promise increased spectral selectivity of artificial sound encoding, and hence might improve speech recognition in background noise as well as processing of music.

Do age and linguistic background alter the audiovisual advantage when listening to speech in the presence of energetic and informational masking?

We examined how the type of masker presented in the background affected the extent to which visual information enhanced speech recognition, and whether the effect was dependent on or independent of age and linguistic competence. In the present study, young speakers of English as a first language (YEL1) and English as a second language (YEL2), as well as older speakers of English as a first language (OEL1), were asked to complete an audio (A) and an audiovisual (AV) speech recognition task in which they listened to anomalous target sentences presented against a background of one of three masker types (noise, babble, and competing speech). All three main effects were found to be statistically significant (group, masker type, A vs. AV presentation type). Interesting two-way interactions were found between masker type and group and between masker type and presentation type; however, no interactions were found between group (age and/or linguistic competence) and presentation type (A vs. AV). The results of this study, while they shed light on the effect of masker type on the AV advantage, suggest that age and linguistic competence have no significant effects on the extent to which a listener is able to use visual information to improve speech recognition in background noise.

Text as a Supplement to Speech in Young and Older Adults.

The purpose of this experiment was to quantify the contribution of visual text to auditory speech recognition in background noise. Specifically, the authors tested the hypothesis that partially accurate visual text from an automatic speech recognizer could be used successfully to supplement speech understanding in difficult listening conditions in older adults, with normal or impaired hearing. The working hypotheses were based on what is known regarding audiovisual speech perception in the elderly from speechreading literature. We hypothesized that (1) combining auditory and visual text information will result in improved recognition accuracy compared with auditory or visual text information alone, (2) benefit from supplementing speech with visual text (auditory and visual enhancement) in young adults will be greater than that in older adults, and (3) individual differences in performance on perceptual measures would be associated with cognitive abilities. Fifteen young adults with normal hearing, 15 older adults with normal hearing, and 15 older adults with hearing loss participated in this study. All participants completed sentence recognition tasks in auditory-only, text-only, and combined auditory-text conditions. The auditory sentence stimuli were spectrally shaped to restore audibility for the older participants with impaired hearing. All participants also completed various cognitive measures, including measures of working memory, processing speed, verbal comprehension, perceptual and cognitive speed, processing efficiency, inhibition, and the ability to form wholes from parts. Group effects were examined for each of the perceptual and cognitive measures. Audiovisual benefit was calculated relative to performance on auditory- and visual-text only conditions. Finally, the relationship between perceptual measures and other independent measures were examined using principal-component factor analyses, followed by regression analyses. Both young and older adults performed similarly on 9 out of 10 perceptual measures (auditory, visual, and combined measures). Combining degraded speech with partially correct text from an automatic speech recognizer improved the understanding of speech in both young and older adults, relative to both auditory- and text-only performance. In all subjects, cognition emerged as a key predictor for a general speech-text integration ability. These results suggest that neither age nor hearing loss affected the ability of subjects to benefit from text when used to support speech, after ensuring audibility through spectral shaping. These results also suggest that the benefit obtained by supplementing auditory input with partially accurate text is modulated by cognitive ability, specifically lexical and verbal skills.

Clinical Outcome After Cochlear Implantation in Patients With Unilateral Hearing Loss Due to Labyrinthitis Ossificans

Cochlear implantation (CI) is the treatment of choice in bilateral labyrinthitis ossificans (LO). The aim of this clinical case study was to evaluate audiologic and subjective outcomes after CI treatment for unilateral hearing loss (UHL) because of LO and to identify optimal timing for treatment. Three subjects (age 40, 54, and 68 yr) with UHL because of LO were enrolled. Duration of deafness was 1.5, 12, and 120 months. After extensive consultation, testing with conventional contralateral routing of signal hearing aid and bone-anchored hearing instrument, CI candidacy was confirmed and CI surgery performed. Test of open-set speech recognition in background noise and sound localization were performed preoperatively, in unaided and aided conditions, and in the CI-aided condition, at 6 and 12 months postoperatively. Subjective assessment via the Speech, Spatial and Qualities scale (SSQ) and the Tinnitus Visual Analogue Scale was performed at preimplant and 12 months postimplant. The data show moderate-to-high hearing benefit after CI in 2 cases and no benefit for the third. SSQ and tinnitus scales show benefit from CI use in both cases. CI treatment should be performed as early as possible, ideally before signs of obliteration are evident. Counseling on all rehabilitation options is important.

The role of binary mask patterns in automatic speech recognition in background noise.

Processing noisy signals using the ideal binary mask improves automatic speech recognition (ASR) performance. This paper presents the first study that investigates the role of binary mask patterns in ASR under various noises, signal-to-noise ratios (SNRs), and vocabulary sizes. Binary masks are computed either by comparing the SNR within a time-frequency unit of a mixture signal with a local criterion (LC), or by comparing the local target energy with the long-term average spectral energy of speech. ASR results show that (1) akin to human speech recognition, binary masking significantly improves ASR performance even when the SNR is as low as -60 dB; (2) the ASR performance profiles are qualitatively similar to those obtained in human intelligibility experiments; (3) the difference between the LC and mixture SNR is more correlated to the recognition accuracy than LC; (4) LC at which the performance peaks is lower than 0 dB, which is the threshold that maximizes the SNR gain of processed signals. This broad agreement with human performance is rather surprising. The results also indicate that maximizing the SNR gain is probably not an appropriate goal for improving either human or machine recognition of noisy speech.

New cochlear implant research coding strategy based on the MP3000™ strategy to reintroduce the virtual channel effect

Conclusion: Results for speech recognition in noise tests when using a new research coding strategy designed to introduce the virtual channel effect provided no advantage over MP3000™. Although statistically significant smaller just noticeable differences (JNDs) were obtained, the findings for pitch ranking proved to have little clinical impact. Objectives: The aim of this study was to explore whether modifications to MP3000 by including sequential virtual channel stimulation would lead to further improvements in hearing, particularly for speech recognition in background noise and in competing-talker conditions, and to compare results for pitch perception and melody recognition, as well as informally collect subjective impressions on strategy preference. Methods: Nine experienced cochlear implant subjects were recruited for the prospective study. Two variants of the experimental strategy were compared to MP3000. The study design was a single-blinded ABCCBA cross-over trial paradigm with 3 weeks of take-home experience for each user condition. Results: Comparing results of pitch-ranking, a significantly reduced JND was identified. No significant effect of coding strategy on speech understanding in noise or competing-talker materials was found. Melody recognition skills were the same under all user conditions.

Neural correlates of age-related declines in frequency selectivity in the auditory midbrain

Reduced frequency selectivity is associated with an age-related decline in speech recognition in background noise and reverberant environments. To elucidate neural correlates of age-related alteration in frequency selectivity, the present study examined frequency response areas (FRAs) of multi-unit clusters in the inferior colliculus of young, middle-aged, and old CBA/CaJ mice. The FRAs in middle-aged and old mice were found to be broader and more asymmetric in shape. In addition to a decrease of closed/complex FRAs in both middle age and old groups, there was a transient decrease in V-shaped FRAs and a concomitant increase in multipeak FRAs in middle age. Intensity coding was also affected by age, as observed in an increase of monotonic responses in middle-aged and old mice. While a decline in low-level activity began in middle age, reduced driven rates at suprathreshold levels occurred later in old age. Collectively, these results support the view that aging alters frequency selectivity by widening excitatory FRAs and that these changes begin to appear in middle age.

Evaluation of the Benefit for Cochlear Implantees of Two Assistive Directional Microphone Systems in an Artificial Diffuse Noise Situation

People with cochlear implants have severe problems with speech understanding in noisy surroundings. This study evaluates and quantifies the effect of two assistive directional microphone systems compared to the standard headpiece microphone on speech perception in quiet surroundings and in background noise, in a laboratory setting developed to reflect a situation whereby the listener is disturbed by a noise with a mainly diffuse character due to many sources in a reverberant room. Thirteen postlingually deafened patients, implanted in the Leiden University Medical Centre with the Clarion CII device, participated in the study. An experimental set-up with 8 uncorrelated steady-state noise sources was used to test speech perception on monosyllabic words. Each subject was tested with a standard headpiece microphone, and the two assistive directional microphones, TX3 Handymic by Phonak and the Linkit array microphone by Etymotic Research. Testing was done in quiet at a level of 65 dB SPL and with decreasing signal-to-noise ratios (SNR) down to -15 dB. Using the assistive directional microphones, speech recognition in background noise improved substantially and was not affected in quiet. At an SNR of 0 dB, the average CVC scores improved from 45% for the headpiece microphone to 67% and 62% for the TX3 Handymic and the Linkit respectively. Compared to the headpiece, the Speech Reception Threshold (SRT) improved by 8.2 dB SNR and 5.9 dB SNR for the TX3 Handymic and the Linkit respectively. The gain in SRT for TX3 Handymic and Linkit was neither correlated to the SRT score with headpiece nor the duration of CI-use. The speech recognition test in background noise showed a clear benefit from the assistive directional microphones for cochlear implantees compared to the standard microphone. In a noisy environment, the significant benefit from these assistive device microphones may allow understanding of speech with greater ease.

Unilateral versus Bilateral Amplification for Adults with Impaired Hearing

This study compared unilateral and bilateral aided speech recognition in background noise in 28 patients being fitted with amplification. Aided QuickSIN (Quick Speech-in-Noise test) scores were obtained for bilateral amplification and for unilateral amplification in each ear. In addition, right-ear directed and left-ear directed recall on the Dichotic Digits Test (DDT) was obtained from each participant. Results revealed that the vast majority of patients obtained better speech recognition in background noise on the QuickSIN from unilateral amplification than from bilateral amplification. There was a greater tendency for bilateral amplification to have a deleterious effect among older patients. Most frequently, better aided QuickSIN performance was obtained in the right ear of participants, despite similar hearing thresholds in both ears. Finally, patients tended to perform better on the DDT in the ear that provided less SNR loss on the QuickSIN. Results suggest that bilateral amplification may not always be beneficial in every daily listening environment when background noise is present, and it may be advisable for patients wearing bilateral amplification to remove one hearing aid when difficulty is encountered understanding speech in background noise.

The effects of changes in head angle on auditory and visual input for omnidirectional and directional microphone hearing aids.

Improving the signal-to-noise ratio (SNR) for individuals with hearing loss who are listening to speech in noise provides an obvious benefit. Although binaural hearing provides the greatest advantage over monaural hearing in noise, some individuals with symmetrical hearing loss choose to wear only one hearing aid. The present study tested the hypothesis that individuals with symmetrical hearing loss fit with one hearing aid would demonstrate improved speech recognition in background noise with increases in head turn. Fourteen individuals were fit monaurally with a Starkey Gemini in-the-ear (ITE) hearing aid with directional and omnidirectional microphone modes. Speech recognition performance in noise was tested using the audiovisual version of the Connected Speech Test (CST v.3). The test was administered in auditory-only conditions as well as with the addition of visual cues for each of three head angles: 0 degrees, 20 degrees, and 40 degrees. Results indicated improvement in speech recognition performance with changes in head angle for the auditory-only presentation mode at the 20 degrees and 40 degrees head angles when compared to 0 degrees. Improvement in speech recognition performance for the auditory + visual mode was noted for the 20 degrees head angle when compared to 0 degrees. Additionally, a decrement in speech recognition performance for the auditory + visual mode was noted for the 40 degrees head angle when compared to 0 degrees. These results support a speech recognition advantage for listeners fit with one ITE hearing aid listening in a close listener-to-speaker distance when they turn their head slightly in order to increase signal intensity.

Benefits of amplification for speech recognition in background noise.

The purpose of the present study was to examine the benefits of providing audible speech to listeners with sensorineural hearing loss when the speech is presented in a background noise. Previous studies have shown that when listeners have a severe hearing loss in the higher frequencies, providing audible speech (in a quiet background) to these higher frequencies usually results in no improvement in speech recognition. In the present experiments, speech was presented in a background of multitalker babble to listeners with various severities of hearing loss. The signal was low-pass filtered at numerous cutoff frequencies and speech recognition was measured as additional high-frequency speech information was provided to the hearing-impaired listeners. It was found in all cases, regardless of hearing loss or frequency range, that providing audible speech resulted in an increase in recognition score. The change in recognition as the cutoff frequency was increased, along with the amount of audible speech information in each condition (articulation index), was used to calculate the "efficiency" of providing audible speech. Efficiencies were positive for all degrees of hearing loss. However, the gains in recognition were small, and the maximum score obtained by an listener was low, due to the noise background. An analysis of error patterns showed that due to the limited speech audibility in a noise background, even severely impaired listeners used additional speech audibility in the high frequencies to improve their perception of the "easier" features of speech including voicing.