摘要:

ObjectiveE-periments were conducted to e-amine the effects of le-ical information on word recognition among normal hearing listeners and individuals with sensorineural hearing loss. The le-ical factors of interest were incorporated in the Neighborhood Activation Model (NAM). Central to this model is the concept that words are recognized relationally in the conte-t of other phonemically similar words. NAM suggests that words in the mental le-icon are organized into similarity neighborhoods and the listener is required to select the target word from competing le-ical items. Two structural characteristics of similarity neighborhoods that influence word recognition have been identified; “neighborhood density” or the number of phonemically similar words (neighbors) for a particular target item and “neighborhood frequency” or the average frequency of occurrence of all the items within a neighborhood. A third le-ical factor, “word frequency” or the frequency of occurrence of a target word in the language, is assumed to optimize the word recognition process by biasing the system toward choosing a high frequency over a low frequency word.DesignThree e-periments were performed. In the initial e-periments, word recognition for consonant-vowel-consonant (CVC) monosyllables was assessed in young normal hearing listeners by systematically partitioning the items into the eight possible le-ical conditions that could be created by two levels of the three le-ical factors, word frequency (high and low), neighborhood density (high and low), and average neighborhood frequency (high and low). Neighborhood structure and word frequency were estimated computationally using a large, on-line le-icon-based Webster’s Pocket Dictionary. From this program 400 highly familiar, monosyllables were selected and partitioned into eight orthogonal le-ical groups (50 words/group). The 400 words were presented randomly to normal hearing listeners in speech-shaped noise (E-periment 1) and “in quiet” (E-periment 2) as well as to an elderly group of listeners with sensorineural hearing loss in the speech-shaped noise (E-periment 3).ResultsThe results of three e-periments verified predictions of NAM in both normal hearing and hearing-impaired listeners. In each e-periment, words from low density neighborhoods were recognized more accurately than those from high density neighborhoods. The presence of high frequency neighbors (average neighborhood frequency) produced poorer recognition performance than comparable conditions with low frequency neighbors. Word frequency was found to have a highly significant effect on word recognition. Le-ical conditions with high word frequencies produced higher performance scores than conditions with low frequency words.ConclusionThe results supported the basic tenets of NAM theory and identified both neighborhood structural properties and word frequency as significant le-ical factors affecting word recognition when listening in noise and “in quiet.” The results of the third e-periment permit e-tension of NAM theory to individuals with sensorineural hearing loss. Future development of speech recognition tests should allow for the effects of higher level cognitive (le-ical) factors on lower level phonemic processing.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

A 35-yr-old male patient experienced a sudden loss of speech understanding due to a bilateral cerebrovascular disease. A detailed summary of audiological and neurological findings was presented. Findings indicated that the presence of Pawaves of the Middle Latency Response (MLR) may be a positive prognosis for improvement in hearing thresholds and speech understanding.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveThe objective of this study was to identify common factors affecting speech perception scores in children with cochlear implants.DesignSpeech perception data for 167 implanted children were collected at two cochlear implant centres in Melbourne and Sydney. The data comprised audition-alone scores on open-set word and sentence tests. Children were selected on the basis that they had a Nucleus 22-electrode cochlear implant. The average age of the children was 5 yr. Information was also collected about 12 factors that may have influenced speech perception scores for each child. Analysis of covariance was used to identify factors that significantly affected speech perception scores. Pearson pairwise correlation coefficients were also calculated for all factors analyzed.ResultsThe analyses in this study identified factors that accounted for 51%, 34%, and 45% of the variance in phoneme, word and sentence perception scores. Scores decreased by 1.4 to 2.4% per year of profound deafness prior to implantation. Children who normally use oral communication scored significantly higher than children normally using sign or simultaneous oral and sign communication. Children implanted in Sydney scored higher on average than children implanted in Melbourne.ConclusionsThe results show that a significant part of the variation in speech perception scores is systematically related to audiological and environmental factors for each child. The reasons for significant differences between children using different communication modes or from different clinics were not identified.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveThe purpose of this investigation was to determine how suddenly diminished auditory feedback affects articulatory behaviors for prelingually deafened children with cochlear implants (CIs).DesignTwo 6-yr-old children served as participants. Considering their level of hearing impairment, one child had above average speech perception and production skills while the other child had e-ceptionally good speech perception and production abilities. Baseline data were collected four times over the course of 2 days with the children wearing their CIs. For three additional days, data were collected while the children wore their CIs (ON condition) and then again after their CIs had been deactivated for 1 hr (OFF condition). Variables assessed included amount of jaw opening, F1, F2, nasal air flow, voice onset time (VOT), voicing duration, and the magnitude and duration of intraoral air pressure (Po). Findings were related to each other and to previously reported phonatory findings from the same two children(Higgins, McCleary, & Schulte, 1999)to determine whether changes in articulatory variables in the OFF condition were consistent with a direct effect of diminished auditory feedback or an indirect influence of suprasegmental parameters.ResultsBoth children e-hibited consistent and significant changes in articulatory parameters in the absence of auditory feedback. Such changes occurred more often for the child who had especially proficient speech perception and production skills. Some changes (i.e., reduced Pofor [p] and reduced nasal air flow for [m]) appeared related to the influence of suprasegmental parameters, in particular, reduced subglottal air pressure. Other effects (i.e., increased F2 for [|g] and reduced VOT for [p]) were suggestive of changes in the children’s abilities to maintain appropriate articulatory placements and timing. Finally, a few changes (reduced jaw opening for [i] and increased Poduration for [p]) may have reflected compensatory strategies to maintain correct tongue placement and enhance temporal distinctions in the absence of auditory feedback.ConclusionsBased on the data of our two participants, it appears that some prelingually deafened children with CIs and good speech perception/production skills rely on auditory feedback to maintain articulatory precision. In the absence of auditory feedback, such children may demonstrate changes in articulatory placement and timing. In addition, data from one of our participants are consistent with the idea that some children may be aware that their articulatory control is compromised in the absence of auditory feedback and attempt to compensate by altering articulatory durations or the range of associated articulatory movements.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveThe purpose of this study was to investigate the applicability of the Speech Intelligibility Inde- (SII) in hearing aid fitting. It was hypothesized that estimated speech intelligibility, based on the SII, could be a more reliable measure than real speech recognition results for comparing hearing aid characteristics.DesignThe test subjects were 29 elderly persons (66 to 80 yr) with mild-to-moderate hearing loss, who were using monaurally fitted linear hearing aids. They were selected from the files at Sahlgrenska hearing clinic. Speech recognition scores were obtained at fi-ed speech-to-noise ratios with Phonemically Balanced (PB) words in speech-weighted noise and in low-frequency noise. A Just-Follow-Conversation (JFC) test was performed with connected speech presented in the same background noises. The subjects were tested without hearing aid and with their hearing aids set at three different frequency responses. Predicted speech recognition scores were calculated for each condition based on the SII, complemented with a correction for sensorineural hearing impairment. The calculations involved speech and noise spectra, pure tone thresholds and insertion gain responses.ResultsFor each condition, the measured speech recognition scores were, on average, well predicted by the calculated scores. The intra-individual standard deviation of the predicted scores was estimated to be about one percent unit. The group results of the JFC test were in agreement with the word recognition results for the aided conditions, but a floor effect was observed for the unaided conditions.ConclusionsSpeech intelligibility prediction based on the modified SII is a valid estimate of speech recognition performance of hearing-impaired persons with mild-to-moderate hearing loss. Estimated intelligibility based on the SII is more reliable than actually measured speech recognition performance, for comparing amplification conditions within subjects.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveInvestigators at the National Acoustic Laboratories have provided a theoretical derivation and e-perimental validation of a formula for setting the ma-imum output of hearing aids(Dillon & Storey, 1998; Storey, Dillon, Yeend, & Wigney, 1998). Given that measurement of discomfort levels for setting maximum output can be both time-consuming and of questionable reliability, the use of a prescriptive formula warrants consideration. In this article, an extensive data base was considered and issues of normal hearing, clinical protocol, age and gender were investigated in an effort to further determine optimal maximum output settings.DesignData were gathered from five previous investigations, for a total of 433 subjects (total ears = 710). Threshold of discomfort (TD) measures were obtained using one of two adaptations of the Ascending Method of Limits, one with category anchors and one without.ResultsSubjects with normal hearing had significantly lower TDs than subjects with hearing loss. A different regression line for measured TDs as a function of hearing level was noted for subjects whose hearing threshold levels fell between 20 and 60 dB HL and those with thresholds above 60 dB HL. When all effects (hearing level, method, age and gender) were considered in a single predictive model for the two threshold groups, only method and threshold were significant predictors of TD. However, for the subjects with thresholds between 20 and 60 dB HL, less than 4% of the variance in TD measures could be accounted for by those factors. For subjects with threshold above 60 dB HL, 22% of the variance in TD measures could be accounted for by those variables.ConclusionsFor both groups of subjects (20 to 60 dB HL and above 60 dB HL) methodology and hearing thresholds are significant predictors of discomfort levels. Age and gender are not. Given the small variance accounted for by any of these factors, measures of discomfort using standardized methodologies seem warranted.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

ObjectiveContralateral suppression of the transient-evoked otoacoustic emissions (TEOAEs) provides a means of studying auditory efferent function, but the temporal dynamics of the refle- are not fully understood. The most fundamental parameter is the time-course of activation of contralateral suppression. The stimulus parameters are likely to be important; this may include temporal dynamics of the suppressor itself. This investigation thus was devoted to the further study of 1) delay of contralateral suppression of TEOAEs—effect of delay of the ipsilateral probe—and 2) temporal variation of the suppressor—effect of amplitude modulation of the contralateral noise stimulus.DesignMeasurements were made in three samples of normal-hearing subjects (Ntotal= 71), employing well-established methods of TEOAE assessment.ResultsStatistically significant contralateral suppression occurred some 60 msec after onset of the contralateral noise; thereafter, the effect was essentially constant (i.e., to >180 msec). The results for click delays less than 60 msec, nevertheless, were systematic and readily fitted by a sloping straight line (dB suppression versus time) reminiscent of the concept of threshold power integration. The onset of suppression may thus be characterized by a time constant. The delay of suppression also was found to be reduced by contralateral amplitude-modulated noise.ConclusionsThese findings reinforce a growing consensus in the literature that, despite initiation perhaps some milliseconds after onset of the contralateral stimulus, there is a substantial delay, i.e., in the tens of milliseconds, before ma-imal suppression is achieved. The e-act time constant of this effect appears to depend upon the combination of probe and suppressor levels, including the temporality of the suppressor. These factors are likely to delimit the role/influence of this refle- in real-world function, favoring perhaps more-or-less sustained suppression that is activated in a time-varying sound environment.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID

摘要:

The extra-cellular cochlear microphonic is believed to be generated predominantly by outer hair cells and therefore it would seem reasonable to assume that the presence of a cochlear microphonic excludes outer hair cell dysfunction. Indeed, a diagnosis of auditory neuropathy might be, and has been, made on the basis of a cochlear microphonic present with an abnormal auditory brainstem response. Animal studies, however, have shown that the cochlear microphonic recorded from the round window is dominated by cellular generators located in the base of the cochlea. Primarily on this basis, it is argued that the presence of a cochlear microphonic does not exclude outer hair cell pathology and so outer hair cell integrity should not necessarily be inferred from the presence of the cochlear microphonic alone. In contrast, the absence of an otoacoustic emission in such cases is consistent with outer hair cell dysfunction.

ISSN:0196-0202    

出版商:OVID    

年代:2001

数据来源: OVID