Connected Speech Test Research Articles

Linguistic and Attitudinal Factors in Normal-Hearing Bilingual Listeners' Perception of Degraded English Passages

Linguistic variables alone cannot fully account for bilingual listeners' perception of English-running speech. In the present study, the authors investigated how linguistic and attitudinal factors, in combination, affect bilingual processing of temporally degraded English passages in quiet and in noise. Thirty-six bilinguals with various linguistic and attitudinal characteristics participated in the study. Bilingual individuals completed questionnaires that assessed their language background, willingness to communicate (WTC), and self-perceived communication competency (SPCC) in English. Participants listened to English passage pairs from the Connected Speech Test, presented at 45 dB HL at 3 rates (unprocessed, expanded, compressed), in quiet and in noise. Language proficiency measures were the most significant linguistic variables, accounting for the largest amount of variance in performance across most conditions. Both WTC and SPCC were associated with performance and contributed to regression models. Subscales assessing listeners' WTC and SPCC in a group were more predictive of performance than communication in an interpersonal or public setting. Performance in noise was more difficult to predict than in quiet. Performance with compression was more difficult to predict than with expansion. To fully understand bilingual clients' perception of English speech, hearing professionals should consider their attitudinal characteristics in addition to language background.

Impact of Visual Cues on Directional Benefit and Preference: Part I—Laboratory Tests

The purpose of the laboratory tests of the current investigation was to examine how visual cues impact directional (DIR) benefit and preference for the DIR microphone hearing aid (re: the omnidirectional [OMNI] microphone). Specifically, three hypotheses were examined: (1) the presence of visual cues would improve OMNI-aided performance to ceiling levels and therefore reduce DIR benefit and preference, (2) DIR benefit measured in the audiovisual (AV) condition could not be predicted by that measured using auditory-only (AO) testing, and (3) with visual cues, listeners with greater lipreading skills would perceive less DIR benefit than did listeners with lesser lipreading skills. Twenty-four adults with sensorineural hearing loss were recruited. Their speech recognition performances were measured in two hearing aid microphone modes (DIR and OMNI), at various signal-to-noise ratios (SNR, -10 to +10 dB in 4-dB steps) and under two presentation conditions (AV and AO) by using the AV version of the Connected Speech Test. Microphone preference (DIR versus OMNI) was also assessed with and without visual cues at each of the SNRs by using the same Connected Speech Test sentences. Lipreading skills were measured using the Utley test. The speech recognition data revealed that the participants obtained significantly less DIR benefit in the AV condition because their AV performances were at the ceiling level. Consistent with this, the likelihood of preferring DIR processing was significantly reduced when visual cues were available to the listeners. Further, DIR benefit measured in the AV condition was not correlated with that measured in the AO condition while being significantly and negatively correlated with lipreading skill. These results suggest that AO laboratory testing overestimates the DIR benefit and preference for DIR processing that hearing aid users may have in most face-to-face conversations in typical SNR, real-world environments. Additionally, because the DIR benefit measured in the AV condition cannot be predicted by the benefit score obtained from traditional AO laboratory testing, the effect of visual cues should be considered in establishing a valid laboratory/clinical environment and protocol for DIR microphone hearing aid testing. In light of these findings, consultations should be provided for hearing aid users with superior lipreading skills to help them adjust their expectations regarding the possibly small perceivable benefit gained from DIR microphone hearing aids.

Speech Understanding Using Surgical Masks: A Problem in Health Care?

Successful communication is necessary in health-care environments. Yet the presence of noise in hospitals, operating rooms, and dental offices may have a deleterious effect on health-care personnel and patients understanding messages accurately. The presence of a surgical mask and hearing loss may further affect speech perception. To evaluate whether a surgical mask had an effect on speech understanding for listeners with normal hearing and hearing impairment when speech stimuli were administered in the presence or absence of dental office noise. Participants were assigned to one of two groups based on hearing sensitivity in this quasi-experimental, cross-sectional study. A total of 31 adults participated in this study (1 talker, 15 listeners with normal hearing, and 15 with hearing impairment). The normal hearing group had thresholds of 25 dB HL or better at the octave frequencies from 250 through 8000 Hz while the hearing loss group had varying degrees and configurations of hearing loss with thresholds equal to or poorer than 25 dB HL for the same octave frequencies. Selected lists from the Connected Speech Test (CST) were digitally recorded with and without a surgical mask present and then presented to the listeners in four conditions: without a mask in quiet, without a mask in noise, with a mask in quiet, and with a mask in noise. A significant difference was found in the spectral analyses of the speech stimuli with and without the mask. The presence of a surgical mask, however, did not have a detrimental effect on speech understanding in either the normal-hearing or hearing-impaired groups. The dental office noise did have a significant effect on speech understanding for both groups. These findings suggest that the presence of a surgical mask did not negatively affect speech understanding. However, the presence of noise did have a deleterious effect on speech perception and warrants further attention in health-care environments.

The Objective and Subjective Evaluation of Low-Frequency Expansion in Wide Dynamic Range Compression Hearing Instruments

The effects of low-frequency expansion on the objective and subjective evaluation of four channel in-the-ear hearing instruments was investigated. Three expansion settings were programmed in each device: expansion off, expansion restricted to channel one, and expansion restricted to channels one and two. Objective evaluations were conducted in quiet (Connected Speech Test) and in noise (Hearing in Noise Test) with speech levels fixed at 40 dB SPL. Subjectively, each participant rated expansion satisfaction in quiet and listening to low-level speech in a sound-treated room then indicated the expansion condition preferred overall. Listeners performed significantly better in quiet and in noise for the Off and Channel 1 conditions than the Channels 1 and 2 condition; however, performance was similar between the Off and Channel 1 conditions. Expansion effects on listener satisfaction ratings depended on the listening environment. Overall, listeners preferred expansion in Channel 1 to expansion in Channels 1 and 2; however, preference was not significantly different between the Channel 1 and Off conditions. Results indicate restricting expansion to 1000 Hz overcomes speech-recognition deficits observed with expansion active across a broader spectrum without significantly reducing subjective benefit or preference.

The Objective and Subjective Evaluation of Multichannel Expansion in Wide Dynamic Range Compression Hearing Instruments

The effects of multichannel expansion on the objective and subjective evaluation of 20 listeners fitted binaurally with 4-channel, digital in-the-ear hearing instruments were investigated. Objective evaluations were conducted in quiet using the Connected Speech Test (CST) and in noise using the Hearing in Noise Test (HINT) at 40, 50, and 60 dB SPL. Subjective evaluations were conducted by having each participant (a) rate their satisfaction regarding the amount of noise reduction they perceived daily and (b) indicate which expansion condition they preferred overall after a 2-week trial. Three expansion settings were programmed into the hearing aids: 4-channel expansion, expansion restricted to Channels 1 and 2 only, and expansion off. Listeners performed significantly better in quiet (CST) and in noise (HINT) for the off condition than for either multichannel condition; however, restricting expansion to Channels 1 and 2 improved objective performance in quiet and in noise relative to the 4-channel condition. Conversely, satisfaction ratings were significantly greater for both multichannel conditions than for the off condition; however, satisfaction ratings were similar for the restricted and the 4-channel conditions. Overall, listeners preferred any form of multichannel expansion to no expansion; however, overall preference was similar for the restricted and the 4-channel conditions. Hearing instrument users prefer the use of multichannel expansion despite the fact multichannel expansion may significantly reduce the recognition of low-level speech in quiet and in noise. Although restricting expansion to Channels 1 and 2 (i.e., 2000 Hz and below) maintained subjective benefit for wide dynamic range compression hearing instrument users, the recognition of low-level speech was not completely preserved.

The Effects of High-Frequency Amplification on the Objective and Subjective Performance of Hearing Instrument Users With Varying Degrees of High-Frequency Hearing Loss

The purpose of the present study was to determine if amplifying beyond 2 kHz affected the objective and subjective performance of hearing instrument users with varying degrees of mild-to-severe high-frequency sensorineural hearing loss. Twenty participants were fitted binaurally with digital completely-in-the-canal devices with 4-channel wide dynamic range compression (Starkey Axent). Each participant used the hearing instruments for two 6-week trial periods. Each hearing instrument was programmed to maximize high-frequency audibility during 1 trial period and minimize high-frequency audibility during the other trial period. Objective evaluations were conducted in quiet using the Connected Speech Test (CST) and in noise using the CST and the Hearing in Noise Test. Subjective performance was evaluated by administering the Abbreviated Profile of Hearing Aid Benefit and a questionnaire. Results indicated that high-frequency amplification significantly improved objective performance in noise and subjective preference in quiet for listeners with varying degrees of mild-to-severe high-frequency hearing loss. Results also suggested that high-frequency amplification may affect subjective preference in noise and overall for listeners with varying degrees of mild-to-severe high-frequency hearing loss when feedback is eliminated. Based on these significant benefits, dispensers should be aware that high-frequency amplification should, at least initially, be provided to the affected high-frequency regions when mild-to-severe hearing loss is present.

Directional hearing aid benefit in listeners with severe hearing loss

The purpose of this investigation was to examine the potential for directional hearing aid benefit in listeners with severe hearing loss at multiple SNRs for both auditory only and audio-visual presentation modes. Speech recognition performance was measured using the connected speech test at six SNRs individually determined for each subject in order to avoid floor and ceiling effects. The results revealed significant directional benefit was present at all tested SNRs in the presence of visual information. For auditory only presentations, significant directional benefit was only present at the least positive SNR. The largest directional benefit was measured at the poorest tested SNR for both auditory only and audio-visual presentation modes. The results of this study generally support small but significant directional for listeners with severe hearing loss benefit in a difficult listening environment both with and without the presence of visual information.SumarioEl objetivo de esta investigación fue examinar el beneficio potencial de los auxiliares auditivos direccionales en personas con hipoacusia severa en múltiples condiciones de señal/ruido (SNR) tanto en modo auditivo como en audio-visual. Se midió el desempeño en el reconocimiento del lenguaje mediante la prueba de lenguaje conectado a seis diferentes SNR, determinados en cada individuo para evitar el efecto de piso/techo. Los resultados revelan un beneficio direccional significativo en las seis condiciones de prueba en presencia de información visual. En la presentación exclusivamente auditiva, el beneficio sólo se presentó con la SNR menos positiva. El mayor beneficio direccional se midió con la SNR mas pobre tanto en el modo auditivo como en el audio-visual. Los resultados generales de este estudio apoyan que existe un beneficio direccional pequeño pero significativo para personas con hipoacusia severa en ambientes sonoros difíciles, con o sin información visual.

Application of Frequency Importance Functions to Directivity for Prediction of Benefit in Uniform Fields

The purpose of the current investigation was to systematically examine two of the assumptions central to the application of Articulation Index weighted Directivity Index (AI-DI) to the prediction of directional benefit across three groups of listeners differentiated by degree and configuration of hearing loss. Specifically, the assumption that (1) changes in speech recognition performance are predictable from frequency specific changes in calculated audibility after applying directivity index (DI) values and (2) applying appropriate frequency importance functions would increase the accuracy of AI-DI predictions of directional benefit were evaluated. The output of a single hearing aid for a speech in noise input was recorded to produce high and low directivity (directional and omnidirectional microphone modes) segments. These segments were then high-pass and low-pass filtered into low- and high-frequency regions and acoustically mixed to generate the eight frequency-specific directivity combinations. All recordings were made through an acoustic manikin placed in a single room, surrounded by five uncorrelated noise sources. The aided sentence recognition, in noise, for three groups of 12 adult participants with symmetrical sensorineural hearing impairment, was then measured across the eight listening conditions. The three groups were differentiated by degree and type of hearing loss including "sloping," "flat," and "severe" configurations. The frequency-specific DI values for each of the eight listening conditions were applied to the calculation of frequency specific noise levels. These corrected noise levels were then used to calculate an Articulation Index using the Speech Intelligibility Index (SII, ). These SII values were then compared with measured speech recognition under the same eight listening conditions. Directional benefit values were then calculated by subtracting the performance of individual participants on the Connected Speech Test (CST) in omnidirectional mode from performance in all other filter conditions. The changes in average DI and AI-DI (using three different frequency importance functions) that existed between omnidirectional and the other seven filter conditions were then calculated for comparison to directional benefit values. The speech recognition data revealed a complex interaction between filter condition and group. Despite this interaction, highly significant positive correlations were found between participants' speech recognition scores and the corresponding SII calculation for all three hearing loss groups. Individual subjects' measured directional benefit was highly correlated with changes in DI. Similar correlations were found for average DI and all three AI-DI weighting methods. As expected, performance and calculated SII values were in good agreement across conditions supporting the hypothesis that DI provides a reasonable frequency-specific estimate of signal-to-noise ratio changes in the test environment. The results further support the use of AI-DI or average DI for prediction of directional benefit. The choice of importance weighting across frequency (flat or frequency importance function based), however, did not improve the accuracy of these predictions; therefore, a simple average DI is advocated. Further, the prediction of absolute directional benefit across hearing loss groups from traditional AI-DI calculations may lead to error if the negative effects of hearing loss on speech understanding, and how these effects vary with degree of hearing loss, are not considered as a contributing factor.

The Effects of Expansion Time Constants on the Objective Performance of Hearing Instrument Users

The present study investigated the effects of expansion time constants on the objective performance of 20 hearing instrument users fitted binaurally with digital in-the-ear products. Objective performance was evaluated in quiet using the Connected Speech Test and in noise using the Hearing in Noise Test. Results indicated that objective performance in quiet and in noise decreased as the expansion time constant increased. Furthermore, expansion time constants affected the objective performance of listeners with varying degrees of hearing loss in a similar manner.

The Effects of Expansion on the Objective and Subjective Performance of Hearing Instrument Users

The present study investigated the effects of expansion on the objective and subjective performance of 20 hearing instrument users fitted binaurally with digital ITE products. Objective performance was evaluated in quiet using the Connected Speech Test and in noise using the Hearing in Noise Test. Subjective performance was evaluated in two ways: (a) by having each participant rate their satisfaction regarding the amount of noise reduction they perceived in each expansion condition on a daily basis and (b) by having each participant indicate which expansion condition they preferred following the completion of a two-week trial. Results indicated that expansion significantly reduced low-level speech perception performance; however, satisfaction and preference ratings significantly increased when using expansion. The effect of degree of hearing loss, expansion kneepoint, and expansion ratio on the effectiveness of expansion for a given listener was discussed.

Quantification of Directional Benefit across Different Polar Response Patterns

The purpose of this study was to assess the relationship between the directivity of a directional microphone hearing aid and listener performance. Hearing aids were fit bilaterally to 19 subjects with sensorineural hearing loss, and five microphone conditions were assessed: omnidirectional, cardioid, hypercardioid, supercardioid, and "monofit," wherein the left hearing aid was set to omnidirectional and the right hearing aid to hypercardioid. Speech perception performance was assessed using the Hearing in Noise Test (HINT) and the Connected Speech Test (CST). Subjects also assessed eight domains of sound quality for three stimuli (speech in quiet, speech in noise, and music). A diffuse soundfield system composed of eight loudspeakers forming the corners of a cube was used to output the background noise for the speech perception tasks and the three stimuli used for sound quality judgments. Results indicated that there were no significant differences in the HINT or CST performance, or sound quality judgments, across the four directional microphone conditions when tested in a diffuse field. Of particular interest was the monofit condition: Performance on speech perception tests was the same whether one or two directional microphones were used.

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.

Audibility-index predictions of normal-hearing and hearing-impaired listeners' performance on the connected speech test.

In a previous study (Sherbecoe & Studebaker, 2002), we derived a frequency-importance function and a transfer function for the audio compact disc version of the Connected Speech Test (CST). The current investigation evaluated the validity of these audibility-index (AI) functions based on how well they predicted data from four published studies that presented the CST to normal-hearing and hearing-impaired subjects. AI values were calculated for the test conditions received by 78 normal-hearing and 72 hearing-impaired subjects from the selected studies. The observed CST scores and AI values for these conditions/subjects were then plotted and the dispersion of the data compared to the expected range based on critical differences. The AI values for the conditions/subjects were also converted into expected CST scores and subtracted from their corresponding observed scores to determine the distribution of the resulting difference scores and the relationship between the difference scores and subject age. Good predictions were obtained for normal-hearing subjects who had been tested under audio-only conditions but not those who had received audiovisual tests. The expected scores for the latter subjects were too low when the AI accounted only for audibility and too high when it included the correction for visual cues from ANSI S3.5-1997. All of the hearing-impaired subjects had been tested under audio-only conditions. In their case, the mean difference between the observed and the expected scores was comparable with the audio-only mean for the normal-hearing subjects when the AI included corrections for speech level distortion and hearing loss desensitization. However, the hearing-impaired subject data had greater variability. The predictions for these subjects also decreased in accuracy when subject age increased beyond 70 yr despite the application of an AI correction for age. The results of this study suggest that the AI functions derived for the CST satisfactorily predict the scores of normal-hearing subjects when they listen in speech babble under audio-only conditions but not when they receive visual cues. To obtain accurate predictions for the audiovisual form of the CST, it will be necessary to develop new ANSI-style AI correction equations for visual cues or new AI functions based on audiovisual test scores. If the current AI functions are used to predict the scores of hearing-impaired listeners tested under audio-only conditions, the AI should include corrections for the effects of speech level and hearing loss. A correction for subject age also could be applied, if it seems appropriate to do so. In either case, however, the predictions are still likely to be less accurate than the predictions for normal-hearing subjects. This may be because speech recognition deficits in people with hearing loss are not due solely to diminished audibility. Hearing-impaired subjects, particularly if they are elderly, also may be more susceptible to masking effects or other factors not accounted for by the AI.

An Examination of Changes in Hearing-Aid Performance and Benefit in the Elderly Over a 3-Year Period of Hearing-Aid Use

This brief report describes the changes in hearing-aid performance and benefit in 9 elderly hearing-aid wearers over a 3-year period following the hearing-aid fitting. Objective measures of hearing-aid performance included three measures of speech recognition: (a) the Nonsense Syllable Test (NST) presented at 65 dB SPL and a +8 dB signal-to-noise ratio (SNR), (b) the Connected Speech Test (CST) presented at 50 dB SPL in quiet, and (c) the CST presented at 65 dB SPL and a +8 dB SNR. Subjective, self-report measures of hearing-aid benefit included the Hearing Aid Performance Inventory (HAPI; B. E. Walden, M. E. Demorest, & E. L. Helper, 1984) and the Hearing Handicap Inventory for the Elderly (HHIE; I. Ventry & B. Weinstein, 1982). Performance and benefit measures were obtained at postfit intervals of 1 month, 6 months, 1 year, 2 years, and 3 years using a standardized measurement protocol. Individual data were evaluated using 95% critical differences established previously for each benefit measure and applied around the scores observed at the 1-month postfit interval. Little evidence was seen for systematic improvement in aided performance or benefit, consistent with that expected from acclimatization, in any participant or for any measure of benefit.

Audibility-index functions for the connected speech test.

A study was performed to derive a frequency importance function (FIF), a performance-intensity funcTIon (PIF), and a transfer function (TF) for the audio compact disc version of the Connected Speech Test (CST). CST passages were masked with talker-spectrum-matched (TSM) noise and presented to two groups of normal-hearing adult subjects. One group (N = 48) listened through a wideband filter, seven low-pass filters, and eight high-pass filters at six signal-to-noise (S/N) ratios. The other group (N = 12) listened through just the wideband filter at 12 S/N ratios. The FIF was based on the data for the first group while the PIF was based on the data for the second group. The results of both groups were used to determine the TF between CST scores and audibility-index (AI) values. The FIF, in 1/3-octave bands, is a bimodal curve with a minor peak at 500 Hz, a major peak at 1600 to 2000 Hz, and a midpoint of 1619 Hz. The PIF in TSM noise and the TF are both asymmetric S-shaped curves; their respective slopes are 12%/dB and 11%/0.0333 AI. Comparisons between these results and the findings of other studies reconfirm that different speech materials have different AI functions. The FIF for the CST overlaps 1/3-octave band functions for continuous discourse and average speech but does not have the same shape as those functions. The TF indicates that CST passages are generally more intelligible than isolated monosyllabic words (NU6 lists) and somewhat less intelligible than continuous discourse. The former result is probably due at least partly to the effects of context whereas the latter result may be due primarily to how clearly the talkers pronounced the speech materials.

Evaluation of an adaptive, directional-microphone hearing aid: Evaluación de un auxiliar auditivo de micrófono direccional adaptable

The effectiveness of adaptive directional processing for improvement of speech recognition in comparison to non-adaptive directional and omnidirectional processing was examined across four listening environments intended to simulate those found in the real world. The test environment was a single, moderately reverberant room with four loudspeaker configurations: three with fixed discrete noise source positions and one with a single panning noise source. Sentence materials from the Hearing in Noise Test (HINT) and Connected Speech Test (CST) were selected as test materials. Speech recognition across all listening conditions was evaluated for 20 listeners fitted binaurally with Phonak Claro behind-the-ear (BTE) style hearing aids. Results indicated improved speech recognition performance with adaptive and non-adaptive directional processing over that measured with the omnidirectional processing across all four listening conditions. While the magnitudes of directional benefit provided to subjects listening in adaptive and fixed directional modes were similar in some listening environments, a significant speech recognition advantage was measured for the adaptive mode in specific conditions. The advantage for adaptive over fixed directional processing was most prominent when a competing noise was presented from the listener's sides (both fixed and panning noise conditions), and was partially predictable from electroacoustically measured directional pattern data.SumarioLa efectividad del procesamiento direccional adaptable para mejorar el reconocimiento del lenguaje en comparación con el procesamiento omnidireccional o el direccional no adaptable, fue examinada en cuatro ambientes diferentes, tratando de simular aquellos encontrados en el mundo real. El ambiente de evaluación fue una habitación moderadamente reverberante con una configuratión de cuatro parlantes: tres con posiciones discretas y fijas de la fuente de ruido y uno con una fuente única de ruido variable. Se seleccionó material de oraciones de la Prueba de Auditión en Ruido (HINT) y de la Prueba de Lenguaje Conectado (CST) como material de evaluatión. El reconocimiento del lenguaje en todas las diferentes condiciones auditivas fue evaluado en 20 sujetos adaptados binauralmente con audifonos retroauriculares (BTE) del tipo Phonak Claro. Los resultados indicaron mejoria en el rendimiento de la función de reconocimiento del lenguaje con procesamiento direccional adaptable o no adaptable, comparado con el medido a través de procesamiento omnidireccional en los cuatro ambientes. En tanto la magnitud del beneficio direccional resultanle fue similar en algunos ambientes de audition para sujetos que escuchan en modo direccional adaptable y fijo, una ventaja significativa en el reconocimiento del lenguaje fue obtenida para el modo adaptable, en condiciones especificas. La ventaja del procesamiento direccional adaptable sobre el fijo fue más prominente cuando se presentaba un ruido de competencia a los lados del sujeto (tanto en condiciones de ruido fijo y variable), y fue parcialmente predecible con base en la información sobre el patrón direccional electroacústicamente medido.

Impact of Compression and Hearing Aid Style on Directional Hearing Aid Benefit and Performance

To evaluate the impact of low-threshold compression and hearing aid style (in-the-ear [ITE] versus behind-the-ear [BTE]) on the directional benefit and performance of commercially available directional hearing aids. Forty-seven adult listeners with mild-to-moderate sensorineural hearing loss were fit bilaterally with one BTE and four different ITE hearing aids. Speech recognition performance was measured through the Connected Speech Test (CST) and Hearing in Noise Test (HINT) for a simulated noisy restaurant environment. For both the HINT and CST, speech recognition performance was significantly greater for subjects fit with directional in comparison with omnidirectional microphone hearing aids. Performance was significantly poorer for the BTE instrument in comparison with the ITE hearing aids when using omnidirectional microphones. No differences were found for directional benefit between compression and linear fitting schemes. No systematic relationship was found between the relative directional benefit and hearing aid style; however, the speech recognition performance of the subjects was somewhat predictable based on Directivity Index measures of the individual hearing aid models. The fact that compression did not interact significantly with microphone type agrees well with previously reported electroacoustic data.

Comparison of Benefits Provided by Different Hearing Aid Technologies

The performance of 40 hearing-impaired adults with the GN ReSound digital BZ5 hearing instrument was compared with performance with linear hearing aids with input compression limiting (AGC-I) or two-channel analog wide dynamic range compression (WDRC) instruments. The BZ5 was evaluated with an omnidirectional microphone, dual-microphone directionality, and a noise reduction circuit in combination with dual-microphone directionality. Participants were experienced hearing aid users who were wearing linear AGC-I or analog WDRC instruments at the time of enrolment. Performance was assessed using the Connected Speech Test (CST) presented at several presentation levels and under various conditions of signal degradation and by the Profile of Hearing Aid Benefit (PHAB). Subjective ratings of speech understanding, listening comfort, and sound quality/naturalness were also obtained using 11-point interval scales. Small performance advantages were observed for WDRC over linear AGC-I, although WDRC did not have to be implemented digitally for these performance advantages to be realized. Substantial performance advantages for the dual microphones over the omnidirectional microphone were observed in the CST results in noise, but participants generally did not perceive these large advantages in everyday listening. The noise reduction circuit provided improved listening comfort but little change in speech understanding.

Performance results of noisy speech enhancement using undecimated wavelets and spectral peak enhancement

This paper presents a new speech enhancement algorithm based upon an undecimated discrete wavelet transform followed by spectral peak enhancement. Experimental data is presented which demonstrates improved automatic speech recognition scores in noisy speech. The new algorithm first removes noise by soft-thresholding in the undecimated wavelet domain. However, the noise reduction process leaves residual noise that impairs intelligibility. In the new algorithm, residual noise removal after the undecimated wavelet denoising scheme is achieved by a nonlinear modification of the Fourier spectrum to enhance the spectral peaks relative to the valleys. Using 30 sentences at each SNR, evaluation of the new algorithm was conducted with the Connected Speech Test (CST), a procedure that ensures that the speech sentences have equal difficulty. For additive white Gaussian noise, significant improvements are observed in the experiment results and it is shown that an effective speech enhancement is obtained by spectral peak enhancement with small decomposition level. The results were variable with babble noise and office noise. Performance results will be presented

Effect of compression ratio on speech recognition and speech-quality ratings with wide dynamic range compression amplification.

This project examined the effect of varying compression ratio on speech recognition and quality. Both listeners with mild-to-moderate sensorineural hearing loss and a control group of listeners with normal hearing participated. Test materials were sentences from the Connected Speech Test (R. M. Cox, G. C. Alexander, & C. Gilmore, 1987) which were digitally processed with linear amplification and wide dynamic range compression amplification with 3 compression ratios. Speech-recognition scores were obtained with sentences in quiet and in noise at a 10-dB signal-to-noise ratio for each amplification condition. Additionally, the participants rated each amplification condition in terms of clarity, pleasantness, ease of understanding, and overall impression. Results indicated that, for speech in quiet, compression ratio had no effect on speech-recognition scores; however, speech-quality ratings decreased as compression ratio increased. For speech in noise, both speech-recognition scores and ratings decreased with increasing compression ratio for the listeners with hearing loss. These results suggest that selection of compression ratio on the basis of speech-quality judgments does not compromise speech recognition.