Speech Discrimination Performance Research Articles

Word-in-noise perception test in children

Background The word-in-noise discrimination test evaluates the phonological aspect of speech based on the detection of the vowels. While word-in-noise perception (WINP) test is one of the speech perception exams and evaluates the ability to understand the meaning of words by discovering the consonants.Until now, all word-in-noise tests have assessed speech discrimination performance, and for the first time, the normal values of the WINP test for adults have been determined. Since the normal values of WINP scores in children have not been reported, our research aimed to determine the normal values of the WINP test in children aged 5 to 13 years.In this cross-sectional study, 120 Persian speaking Iranain children with normal hearing thresholds were evaluated from the beginning to the end of spring 2023. We divided them into 4 age groups (A = 5–7 < years, B = 7–9 < years, C = 9–11 < years, D = 11–13 < years). The evaluations included general audiology tests and WINP tests using homtonic-monosyllabic words (HMWs) at a signal-to-noise ratio of 5 dB.ResultsSignificant difference was observed between the mean scores of the WINP test in age group A (54%) compared to age group B (66%), (Pv = 0.04). Also, the differences between the mean scores of age group A compared to age groups C (70%) and D (69%) were significant (Pv = 0.01, Pv = 0.03).ConclusionsThis article presented the norm values of WINP test scores for Persian speaking Iranian children aged 5 to 13 years. The norm values of WINP test scores in the age group of 5–7 years were lower than in the age groups of 7–13 years. The biggest change in the performance of speech perception in noise was observed in the age range of 7–9 years.

Evaluation of the Listening Environment of Bilateral Cochlear Implant Users through Data Logging: A Comparison of Bilateral Simultaneous and Sequential Implantation.

To evaluate the listening conditions of bilateral cochlear implant (CI) users in their daily living environment. Retrospective study. University hospital. Thirty-one adult CI users 16 years or older; 18 underwent sequential surgery, and 13 underwent simultaneous surgery. Inclusion criteria included the availability of CI data logging features and a minimum duration of binaural use of 6 months. Retrospective analysis of data obtained from the automatic scene classifier data logging system. Comparison of data logging and maximum speech discrimination scores of the two surgery groups (sequential vs. simultaneous) to investigate the potential influence of these factors on the listening conditions of CI users. The maximum speech discrimination score of the second CI in the sequential group was significantly worse than that of any other CI in the sequential and simultaneous CI groups. Additionally, the longer the interval between surgeries, the more significant the difference in "time on air" between the first and the second CIs. The second CI in sequential CI surgery had a shorter "time on air" than the first or the bilateral simultaneous CIs; the second CI was also used more frequently in noisy and speech with background noise environments. A second CI may be more frequently used in challenging listening environments because of its binaural auditory effect, despite its lower speech discrimination performance. The timing of sequential implantation and the potential impact of binaural hearing should be considered when developing rehabilitation strategies for individuals with bilateral CIs.

Discriminating spatialised speech in complex environments in multiple sclerosis

People with multiple sclerosis (pwMS) frequently present with deficits in binaural processing used for sound localization. This study examined spatial release from speech-on-speech masking in pwMS, which involves binaural processing and additional higher level mechanisms underlying streaming, such as spatial attention.26 pwMS with mild severity (Expanded Disability Status Scale score <3) and 20 age-matched controls listened via headphones to pre-recorded sentences from a standard list presented simultaneously with eight-talker babble. Virtual acoustic techniques were used to simulate sentences originating from 0°, 20°, or 50° on the interaural horizontal plane around the listener whilst babble was presented continuously at 0° azimuth, and participants verbally repeated the target sentence. In a separate task, two simultaneous sentences both containing a colour and number were presented, and participants were required to report the target colour and number. Both competing sentences could originate from 0°, 20°, or 50° on the azimuthal plane. Participants also completed a series of neuropsychological assessments, an auditory questionnaire, and a three-alternative forced-choice task that involved the detection of interaural time differences (ITDs) in noise bursts.Spatial release from masking was observed in both pwMS and controls, as response accuracy in the two speech discrimination tasks improved in the spatially separated conditions (20° and 50°) compared with the co-localised condition. However, pwMS demonstrated significantly less spatial release (18%) than controls (28%) when discriminating colour/number coordinates. At 50° separation, pwMS discriminated significantly fewer coordinates (77%) than controls (89%). In contrast, pwMS had similar performances to controls when sentences were presented in babble, and for the basic ITD discrimination task. Significant correlations between speech discrimination performance and standardized neuropsychological scores were observed across all spatial conditions.Our findings suggest that spatial hearing is likely to be implicated in pwMS, thereby affecting the perception of competing speech originating from various locations.

Effect of cochlear implant side on early speech processing in adults with single-sided deafness

ObjectiveIn binaurally deaf subjects, speech processing particularly benefits from a cochlear implant (CI) in the right ear, which is contralateral to the commonly left speech-dominant hemisphere. However, it is unclear whether such effects of implantation side also occur in speech processing in patients with single-sided deafness (SSD). MethodsLateralization of N1 responses was analyzed with a high-density electroencephalogram (EEG) in fourteen adults with postlingually acquired left or right SSD who received a CI in adulthood. During recording, patients performed a speech and a pure-tone discrimination task. Lateralization of N1 responses was assessed by side-specific global field power (GFP) and compared (a) between normal hearing and CI-implanted ears within subjects and (b) between implantation sides across subjects. ResultsN1 responses were stronger in the contralateral than in the ipsilateral hemisphere during stimulation of the normal hearing ear (except for left speech stimulation), and was bilateral symmetric with CI stimulation on either side. A significant correlation between speech discrimination performance and left lateralization was found across subjects for the left CI ear. ConclusionsCI stimulation altered auditory processing across hemispheres. Speech discrimination in left CI-implanted SSD patients improved with left lateralization of the N1 response. SignificanceSide-specific rehabilitation in SSD patients might improve speech processing across hemispheres.

Transplantation of adipose-derived stromal cells protects functional and morphological auditory nerve integrity in a model of cochlear implantation.

Cochlear implants are considered the gold standard therapy for subjects with severe hearing loss and deafness. Cochlear implants bypass the damaged hair cells and directly stimulate spiral ganglion neurons (SGNs) of the auditory nerve. Hence, the presence of functional SGNs is crucial for speech perception in electric hearing with a cochlear implant. In deaf individuals, SGNs progressively degenerate due to the lack of neurotrophic support, normally provided by sensory cells of the inner ear. Adipose-derived stromal cells (ASCs) are known to produce neurotrophic factors. In a guinea pig model of sensory hearing loss and cochlear implantation, ASCs were autologously transplanted into the scala tympani prior to insertion of a cochlear implant on one side. Electrically evoked auditory brain stem responses (eABR) were recorded 8 weeks after cochlear implantation. At conclusion of the experiment, the cochleae were histologically evaluated. Compared to untreated control animals, transplantation of ASCs resulted in an increased number of SGNs and their peripheral neurites. In ASC-transplanted animals, mean eABR thresholds were lower and suprathreshold amplitudes larger, suggesting a larger population of intact auditory nerve fibers. Moreover, when compared to controls, amplitude-level functions of eABRs in ASC transplanted animals demonstrated steeper slopes in response to increasing interphase gaps (IPGs), indicative of better functionality of the auditory nerve. In summary, results suggest that transplantation of autologous ASCs into the deaf inner ear may have protective effects on the survival of SGNs and their peripheral processes and may thus contribute to long-term benefits in speech discrimination performance in cochlear implant subjects.

Speech discrimination impairments as a marker of disease severity in multiple sclerosis

BackgroundMultiple Sclerosis (MS) pathology is likely to disrupt central auditory pathways, thereby affecting an individual's ability to discriminate speech from noise. Despite the importance of speech discrimination in daily communication, it's characterization in the context of MS remains limited. This cross-sectional study evaluated speech discrimination in MS under "real world" conditions where sentences were presented in ecologically valid multi-talker speech or broadband noise at several signal-to-noise ratios (SNRs). MethodsPre-recorded Bamford-Kowal-Bench sentences were presented at five signal-to-noise ratios (SNR) in one of two background noises: speech-weighted noise and eight-talker babble. All auditory stimuli were presented via headphones to control (n = 38) and MS listeners with mild (n = 20), moderate (n = 16) and advanced (n = 10) disability. Disability was quantified by the Kurtzke Expanded Disability Status Scale (EDSS) and scored by a neurologist. All participants passed a routine audiometric examination. ResultsDespite normal hearing, MS psychometric discrimination curves which model the relationship between signal-to-noise ratio (SNR) and sentence discrimination accuracy in speech-weighted noise and babble did not change in slope (sentences/dB) but shifted to higher SNRs (dB) compared to controls. The magnitude of the shift in the curve systematically increased with greater disability. Furthermore, mixed-effects models identified EDSS score as the most significant predictor of speech discrimination in noise (odds ratio = 0.81; p < 0.001). Neither age, sex, disease phenotype or disease duration were significantly associated with speech discrimination performance in noise. Only MS listeners with advanced disability self-reported audio-attentional difficulty in a questionnaire designed to reflect auditory processing behaviours in daily life. ConclusionSpeech discrimination performance worsened systematically with greater disability, independent of age, sex, education, disease duration or disease phenotype. These results identify novel auditory processing deficits in MS and highlight that speech discrimination tasks may provide a viable non-invasive and sensitive means for disease monitoring in MS.

Influence of temporal resolution skills in speech discrimination abilities of older subjects.

SUMMARYCompromised temporal resolving power of the auditory system can be one of the main factors contributing to poor speech perception skills in the elderly. Very few of the earlier studies have systematically examined this aspect. Hence, the current study was designed with the following objectives: 1) To establish normative database of Gaps in Noise (GIN) test in elderly population in an Indian context. 2) To determine the relationship between speech discrimination skills and temporal resolution abilities in elderly individuals with normal hearing sensitivity. Thirty normal hearing elderly individuals (age range: 55-75 years; mean age: 59.86 ± 4.11 years) participated in the study. The audiological evaluation comprised of tympanometry, puretone and speech audiometry (Speech Reception Threshold-SRT, Speech Discrimination Score-SDS) and GIN. The results of the present study revealed mean Gap Detection Threshold (GDT) of 8.7 msec (SD = 3.38) in the right ear and 8.83 msec (SD = 2.86) in the left ear for the older participants. The mean Total Percentage Score (TPS) in the right ear was 47% (SD = 11.92) and 45% (SD = 11.29) in the left ear. These results suggest that temporal resolution abilities are poor in the elderly compared to the young and middle-aged group. There was no significant ear based difference on either GDT or TPS. The GDT was inversely correlated with speech discrimination performance. The TPS was positively correlated with SDS. This study clearly demonstrated a positive relationship between temporal resolution abilities and speech discrimination. The current database might be useful when assessing temporal resolution abilities in hearing impaired elderly individuals. Furthermore, all elderly individuals should undergo temporal resolution evaluation, irrespective of their hearing status, during audiological assessment.

Increased activity in frontal motor cortex compensates impaired speech perception in older adults.

Understanding speech in noisy environments is challenging, especially for seniors. Although evidence suggests that older adults increasingly recruit prefrontal cortices to offset reduced periphery and central auditory processing, the brain mechanisms underlying such compensation remain elusive. Here we show that relative to young adults, older adults show higher activation of frontal speech motor areas as measured by functional MRI during a syllable identification task at varying signal-to-noise ratios. This increased activity correlates with improved speech discrimination performance in older adults. Multivoxel pattern classification reveals that despite an overall phoneme dedifferentiation, older adults show greater specificity of phoneme representations in frontal articulatory regions than auditory regions. Moreover, older adults with stronger frontal activity have higher phoneme specificity in frontal and auditory regions. Thus, preserved phoneme specificity and upregulation of activity in speech motor regions provide a means of compensation in older adults for decoding impoverished speech representations in adverse listening conditions.

Factors Affecting Speech Discrimination in Children with Cochlear Implants: Evidence from Early-Implanted Infants.

To learn words and acquire language, children must be able to discriminate and correctly perceive phonemes. Although there has been much research on the general language outcomes of children with cochlear implants (CIs), little is known about the development of speech perception with regard to specific speech processes, such as speech discrimination. The purpose of this study was to investigate the development of speech discrimination in infants with CIs and identify factors that might correlate with speech discrimination skills. Using a Hybrid Visual Habituation procedure, we tested infants with CIs on their ability to discriminate the vowel contrast /i/-/u/. We also gathered demographic and audiological information about each infant. Children who had received CIs before 2 yr of age served as participants. We tested the children at two post cochlear implantation intervals: 2-4 weeks post CI stimulation (N = 17) and 6-9 mo post CI stimulation (N = 10). The infants' mean looking times during the novel versus old trials of the experiment were measured. A linear regression model was used to evaluate the relationship between the normalized looking time difference and the following variables: chronological age, age at CI stimulation, gender, communication mode, and best unaided pure-tone average. We found that the best unaided pure-tone average predicted speech discrimination at the early interval. In contrast to some previous speech perception studies that included children implanted before 3 yr of age, age at CI stimulation did not predict speech discrimination performance. The results suggest that residual acoustic hearing before implantation might facilitate speech discrimination during the early period post cochlear implantation; with more hearing experience, communication mode might have a greater influence on the ability to discriminate speech. This and other studies on age at cochlear implantation suggest that earlier implantation might not have as large an effect on speech perception as it does on other language skills.

The long-term results of speech perception in elderly cochlear implant users

Objectives: To evaluate the speech discrimination performance of elderly post-lingually deafened cochlear implant (CI) users and the stability of performance over time relative to a control group of younger CI users.Methods: The study group consisted of 20 native Dutch speaking, post-lingually deafened CI users, aged 70 or older at the time of implantation. Controls were patients aged 40–60 years at implantation and included according to the same inclusion criteria (except age). Linear mixed models assessed speech recognition scores between groups, the variability of their performance, and stability over time.Results: 20 elderly and 37 controls were included. The mean follow-up was 4.4 and 5.3 years for elderly and controls, respectively. There was no significant difference in average speech discrimination between both groups. The elderly group had a larger intra-subject variability over time. There was no significant effect of follow-up on the speech discrimination, indicating a stable performance over time.Discussion: This study has a longer follow-up than methodologically comparable previous studies. We found no difference in speech discrimination between elderly patients and controls and no deterioration of performance over time. The subjects in the elderly group exhibit a larger variability around their mean performance.Conclusion: Speech recognition in both elderly and younger adult CI users is stable over time and is not significantly related to the age of implantation.

Dynamic modulation of shared sensory and motor cortical rhythms mediates speech and non-speech discrimination performance.

Oscillatory models of speech processing have proposed that rhythmic cortical oscillations in sensory and motor regions modulate speech sound processing from the bottom-up via phase reset at low frequencies (3–10 Hz) and from the top-down via the disinhibition of alpha/beta rhythms (8–30 Hz). To investigate how the proposed rhythms mediate perceptual performance, electroencephalographic (EEG) was recorded while participants passively listened to or actively identified speech and tone-sweeps in a two-force choice in noise discrimination task presented at high and low signal-to-noise ratios. EEG data were decomposed using independent component analysis and clustered across participants using principle component methods in EEGLAB. Left and right hemisphere sensorimotor and posterior temporal lobe clusters were identified. Alpha and beta suppression was associated with active tasks only in sensorimotor and temporal clusters. In posterior temporal clusters, increases in phase reset at low frequencies were driven by the quality of bottom-up acoustic information for speech and non-speech stimuli, whereas phase reset in sensorimotor clusters was associated with top-down active task demands. A comparison of correct discrimination trials to those identified at chance showed an earlier performance related effect for the left sensorimotor cluster relative to the left-temporal lobe cluster during the syllable discrimination task only. The right sensorimotor cluster was associated with performance related differences for tone–sweep stimuli only. Findings are consistent with internal model accounts suggesting that early efferent sensorimotor models transmitted along alpha and beta channels reflect a release from inhibition related to active attention to auditory discrimination. Results are discussed in the broader context of dynamic, oscillatory models of cognition proposing that top-down internally generated states interact with bottom-up sensory processing to enhance task performance.

Suppression of the µ Rhythm during Speech and Non-Speech Discrimination Revealed by Independent Component Analysis: Implications for Sensorimotor Integration in Speech Processing

BackgroundConstructivist theories propose that articulatory hypotheses about incoming phonetic targets may function to enhance perception by limiting the possibilities for sensory analysis. To provide evidence for this proposal, it is necessary to map ongoing, high-temporal resolution changes in sensorimotor activity (i.e., the sensorimotor μ rhythm) to accurate speech and non-speech discrimination performance (i.e., correct trials.)MethodsSixteen participants (15 female and 1 male) were asked to passively listen to or actively identify speech and tone-sweeps in a two-force choice discrimination task while the electroencephalograph (EEG) was recorded from 32 channels. The stimuli were presented at signal-to-noise ratios (SNRs) in which discrimination accuracy was high (i.e., 80–100%) and low SNRs producing discrimination performance at chance. EEG data were decomposed using independent component analysis and clustered across participants using principle component methods in EEGLAB.ResultsICA revealed left and right sensorimotor µ components for 14/16 and 13/16 participants respectively that were identified on the basis of scalp topography, spectral peaks, and localization to the precentral and postcentral gyri. Time-frequency analysis of left and right lateralized µ component clusters revealed significant (pFDR<.05) suppression in the traditional beta frequency range (13–30 Hz) prior to, during, and following syllable discrimination trials. No significant differences from baseline were found for passive tasks. Tone conditions produced right µ beta suppression following stimulus onset only. For the left µ, significant differences in the magnitude of beta suppression were found for correct speech discrimination trials relative to chance trials following stimulus offset.ConclusionsFindings are consistent with constructivist, internal model theories proposing that early forward motor models generate predictions about likely phonemic units that are then synthesized with incoming sensory cues during active as opposed to passive processing. Future directions and possible translational value for clinical populations in which sensorimotor integration may play a functional role are discussed.

Early combination treatment with intratympanic steroid injection in severe to profound sudden sensorineural hearing loss improves speech discrimination performance

The objective of the study was to determine the therapeutic efficacy of early combined treatment with intratympanic steroid injection (ITSI) in patients with severe to profound sudden sensorineural hearing loss (SSNHL), who did not respond to initial systemic steroid treatment (SST). The study design included historical controlled trials (retrospective analysis for the SST group). Patients (n = 73; 38 women and 35 men) diagnosed with severe to profound SSNHL at the time of their first visit in tertiary referral centers were recruited. Among these 73 patients, 30 patients who showed no early response within a week after the start of initial SST were prospectively included as the ITSI group. ITSI was performed twice a week for two consecutive weeks. In contrast, 43 patients with the same condition who did not receive ITSI were retrospectively included as the SST group. For each group, pure-tone audiogram (PTA) and speech discrimination score (SDS) tests were performed before SST and more than 2 months after termination of treatment in each group. After termination of each treatment, the final average gain on PTA showed no significant difference between the two groups; however, the final average gain of SDS demonstrated a significantly better recovery in the ITSI group. ITSI as part of an early combined therapy represents an effective treatment in terms of the improvement of SDS in severe to profound SSNHL showing no early response to initial SST.

Transitioning Hearing Aid Users with Severe and Profound Loss to a New Gain/Frequency Response: Benefit, Perception, and Acceptance

Adults with severe and profound hearing loss tend to be long-term, full-time users of amplification who are highly reliant on their hearing aids. As a result of these characteristics, they are often reluctant to update their hearing aids when new features or signal-processing algorithms become available. Due to the electroacoustic constraints of older devices, many severely and profoundly hearing-impaired adults continue to wear hearing aids that provide more low- and mid-frequency gain and less high-frequency gain than would be prescribed by the National Acoustic Laboratories' revised formula with profound correction factor (NAL-RP). To investigate the effect of a gradual change in gain/frequency response on experienced hearing-aid wearers with moderately severe to profound hearing loss. Double-blind, randomized controlled trial. Twenty-three experienced adult hearing-aid users with severe and profound hearing loss participated in the study. Participants were selected for inclusion in the study if the gain/frequency response of their own hearing aids differed significantly from their NAL-RP prescription. Participants were assigned either to a control or to an experimental group balanced for aided ear three-frequency pure-tone average (PTA) and age. Participants were fitted with Siemens Artis 2 SP behind-the-ear (BTE) hearing aids that were matched to the gain/frequency response of their own hearing aids for a 65 dB SPL input level. The experimental group progressed incrementally to their NAL-RP targets over the course of 15 wk, while the control group maintained their initial settings throughout the study. Aided speech discrimination testing, loudness scaling, and structured questionnaires were completed at 3, 6, 9, 12, and 15 wk postfitting. A paired comparison between the old and new gain/frequency responses was completed at 1 and 15 wk postfitting. Statistical analysis was conducted to examine differences between the experimental and control groups and changes in objective performance and subjective perception over time. The results of the study showed that participants in the experimental group were subjectively accepting of the changes to their amplification characteristics, as evidenced by nonsignificant changes in the ratings of device performance over time. Perception of loudness, sound quality, speech intelligibility, and own voice volume did not change significantly throughout the study. Objectively, participants in the experimental group demonstrated poorer speech discrimination performance as the study progressed, although there was no change in objective loudness perception. According to the paired comparison, there was an overall subjective preference for the original gain/frequency response among all participants, although participants in the experimental group did show an increase in preference for the NAL-RP response by the end of the study. Based on the findings of this study, we suggest that undertaking a gradual change to a new gain/frequency response with severely and profoundly hearing-impaired adults is a feasible procedure. However, we recommend that clinicians select transition candidates carefully and initiate the procedure only if there is a clinical reason for doing so. A validated prescriptive formula should be used as a transition target, and speech discrimination performance should be monitored throughout the transition.

Nonsensory factors in speech perception

The nature of developmental differences was examined in a speech discrimination task, the change/no-change procedure, in which a varying number of speech stimuli are presented during a trial. Standard stimuli are followed by comparison stimuli that are identical to or acoustically different from the standard. Fourteen adults and 30 4- and 5-year-old children were tested with three speech contrast pairs at a variety of signal-to-noise ratios using various numbers of standard and comparison stimulus presentations. Adult speech discrimination performance followed the predictions of the multiple looks hypothesis [N. F. Viemeister and G. H. Wakefield, J. Acoust. Soc. Am. 90, 858–865 (1991)]; there was an increase in d by a factor of 1.4 for a doubling in the number of standard and comparison stimulus presentations near d values of 1.0. For children, increasing the number of standard stimuli improved discrimination performance, whereas increasing the number of comparisons did not. The multiple looks hypothesis did not explain the children’s data. They are explained more parsimoniously by the developmental weighting shift [Nittrouer et al., J. Acoust. Soc. Am. 101, 2253–2266 (1993)], which proposes that children attend to different aspects of speech stimuli from adults. [Work supported by NIDCD and ASHF.]

Mismatch Negativity Brain Response as an Index of Speech Perception Recovery in Cochlear-Implant Recipients

Speech-discrimination performance and the mismatch negativity (MMN) response elicited by vowel changes were used to track vowel-perception improvement of 5 adult cochlear-implant (CI) recipients. The MMN was recorded several times during the first 3 years after CI activation. Artefacts, presumably caused by CI, contaminated most of the brain responses until 1 year after CI activation. We found that speech discrimination improved over time and the MMN, observed in all patients after 2.5 years of CI use, was first seen for the larger vowel difference and later for the smaller one.

An association between mothers’ speech clarity and infants’ speech discrimination skills

AbstractThe quality of speech directed towards infants may play an important role in infants’ language development. However, few studies have examined the link between the two. We examined the correlation between maternal speech clarity and infant speech perception performance in two groups of Mandarin‐speaking mother–infant pairs. Maternal speech clarity was assessed using the degree of expansion of the vowel space, a measure previously shown to reflect the intelligibility of words and sentences. Speech discrimination in the infants (6–8 and 10–12‐month‐olds) was measured using a head‐turn task. The results show that mothers’ vowel space area is significantly correlated with infants’ speech discrimination performance. Socioeconomic data from both parents show that the result cannot be attributed to parental socioeconomic factors. This study is correlational and therefore a causal relationship cannot be firmly established. However, the results are consistent with the view that maternal speech clarity directly affects infants’ early language learning.

Is there a relationship between speech and nonspeech auditory processing in children with dyslexia?

A group of 8 young teenagers with dyslexia were compared to age-matched control participants on a number of speech and nonspeech auditory tasks. There were no differences between the control participants and the teenagers with dyslexia in forward and simultaneous masking, nor were there any differences in frequency selectivity as indexed by performance with a bandstop noise. Thresholds for backward masking in a broadband noise were elevated for the teenagers with dyslexia as a group. If this deficit in backward masking had an influence on speech perception, we might expect the perception of "ba" versus "da" to be affected, as the crucial second formant transition is followed by a vowel. On the other hand, as forward masking is not different in the two groups, we would expect the perception of "ab" versus "ad" to be unaffected, as the contrastive second formant transition is preceded by a vowel. Overall speech identification and discrimination performance for these two contrasts was superior for the control group but did not differ otherwise. Thus, the clear group deficit in backward masking in the group with dyslexia has no simple relationship to the perception of crucial acoustic features in speech. Furthermore, the deficit for nonspeech analogues of the speech contrasts (second formants in isolation) was much less marked than for the speech sounds, with 75% of the listeners with dyslexia performing equivalently to control listeners. The auditory deficit cannot therefore be simply characterized as a difficulty in processing rapid auditory information. Either there is a linguistic/phonological component to the speech perception deficit, or there is an important effect of acoustic complexity.

Real-world performance of headset active noise reduction systems

Active noise reduction (ANR) in headsets promotes the electro-acoustic cancellation of sound within the ear cups of a hearing protector. Operating at frequencies below 1000 Hz, ANR augments attenuation where passive protection is minimal. Personal ANR can reduce the potential for hazardous noise exposure and can facilitate auditory communications. ANR system performance has been characterized to assist purchasing departments in making informed decisions about commercial devices suitable for use in high-noise environments such as helicopters and tracked vehicles. Test methods were developed to assess: (a) active attenuation properties, (b) issues of fitting integrity, (c) speech discrimination performance, (d) saturation or overload threshold limit, and (e) general suitability for long-term use. When properly designed and applied, personal ANR can enhance the listening environment for the user. Nonetheless, performance limitations have been identified in certain devices. Some tended to overload easily or to cease operating under adverse conditions, and others became unstable when the seal around the ear was broken. Proper fitting is pivotal to satisfactory ANR operation, particularly in units with low overload tolerance. Ultimately, the function of any ANR system must be understood in relation to its intended operating environment.

対話方式による語音聴力検査法

Speech discrimination and hearing aid performance in patients with hearing loss have been evaluated by speech audiometry where a tape or CD is utilized as a sound source. Since all sound samples in a list on the tape or CD are consecutively presented to the examinee, this conventional method provides the perception rate of the whole list. It has been difficult however, to evaluate the perception of a specific sound in the list.We developed a new method of interactive speech audiometry. Using this method, the patient's response to each sound sample can be monitored at any required sound level. All sound samples such as the 5 vowels, 13 consonant-vowel syllables, and sentences are stored in a computer as sound files. Any sound sample can be randomly selected to present to the examinee, who replies verbally. Interactive speech audiometry can provide a more accurate evaluation of speech discrimination in patients with hearing loss.