The purpose of this study was to investigate the effects of a 500 Hz and 3,150 Hz one-third octave band augmentation on the speech discrimination ability of listeners with cochlear hearing impairments. The results were analyzed both within the experimental group of subjects included in the present study and in comparison with data collected on a control group of normal hearing subjects reported earlier.

The accurate perception of spoken English is influenced by many variables, including the listener's native language, reverberation, and background noise. Few studies of speech perception by bilingual listeners have carefully controlled for second language proficiency and even fewer have presented speech in everyday listening environments that contain noise and reverberation. In the present study, detailed language background, language proficiency information, and individual language samples were collected and the speech stimuli were presented in a variety of quiet, noisy, and reverberant listening environments. The effects of noise and reverberation on the perception of American English monosyllabic words was examined for two groups of young listeners with normal hearing: 1) monolingual American English speakers and 2) Spanish-English bilinguals who acquired both languages prior to age 6 years, exhibited similar spoken proficiency in both languages, and spoke English without a noticeable accent. An innovative test of virtual speech perception was used to assess word recognition in two listening environments typical of everyday communication: a simulated noisy anechoic environment and a simulated noisy reverberant environment. Word recognition was also measured in quiet and in an unprocessed noisy environment. For each noisy listening environment (unprocessed, anechoic, reverberant), three signal-to-noise ratios were employed. Results indicate that early bilingualism negatively affects perception of words presented in noisy listening environments. Significantly poorer word recognition was observed for the bilingual listeners than for the monolingual listeners in all three noisy environments and at all noise levels. Both groups exhibited similar word recognition in quiet. The results were surprising considering the high level of spoken language proficiency exhibited by all bilingual listeners. It is often assumed that highly proficient Spanish-English speakers are equally proficient at understanding English; however, these data indicate that the speech understanding of this group may be overestimated in natural listening situations.

This study examined the effects of bilingualism on speech recognition in noise performance of young normal-hearing Spanish-English bilinguals across several signal-to-noise ratios (SNR). The estimated signal-to-noise ratio needed for 50% correct recognition performance obtained for bilingual listeners was compared to young normal-hearing monolingual listeners of both English and Spanish. The estimated mean SNR needed for 50% correct recognition was significantly higher (i.e., poorer) for the bilingual than for the monolingual English listeners. The Spanish language performance of the bilingual listeners did not significantly differ from that of the monolingual Spanish listeners. The bilinguals were then divided into subgroups based on age of acquisition of the second language. Bilinguals were subdivided into early and later learners of English and further comparisons were made. The average estimated SNR needed for 50% correct recognition for the early bilinguals did not differ statistically from that of monolingual listeners in either the English or the Spanish language testing. The SNR obtained for 50% correct recognition of English words was significantly higher for the late bilinguals than for the monolingual English listeners. For Spanish words, the mean SNRs obtained for 50% correct recognition for the later bilinguals and the monolingual Spanish speakers did not differ statistically from one another. These results suggest that caution should be used when assessing speech-in-noise performance in the second language of bilingual patients because separate norms may be needed for this population. Age of acquisition of the second language should be considered as a confounding factor in speech-in-noise performance of bilingual listeners.

Thesis (M. Communication Pathology)--University of Pretoria, 2009. / Includes bibliographical references.

Thesis (M. Aud.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (p. 87-98). Also available via the World Wide Web.

With reductions in the age criterion for cochlear implantation, the need for age-appropriate measures of speech perception skills has increased. One recently developed tool that shows great promise for the clinical assessment of auditory speech perception capacity in young children with cochlear implants is the On-Line Imitative Test of Speech-Pattern Contrast Perception (OlimSpac). The OlimSpac requires a child to imitate nonword utterances by providing a verbal response. The child's perceptual abilities are inferred from the child's productions through having a listener, who is masked to the stimulus select the utterance produced by the child in an eight-alternative force-choice task. Although the OlimSpac has the potential for use in children with cochlear implants, the specific role of measured speech production abilities on performance has yet to be systematically examined. Thus, the main objective of the present study was to examine the influence of speech production abilities on OlimSpac performance in an auditory-visual (A-V) and auditory-only (A-O) condition in young children with cochlear implants relative to an articulation-matched sample of normal hearing peers. A secondary objective was to determine whether the presentation modality affected a child's OlimSpac performance. A matched pair design was used to compare the OlimSpac performance of ten children with cochlear implants (ages 29 to 76 months) to normal hearing peers (ages 27 to 73 months). Each child with cochlear implants was matched to a child with normal hearing from a sampled population of 22 normal hearing participants based on word-level articulation skills, as measured by the GFTA-2, accounting for hearing age and gender. The OlimSpac software generated a score for a single contrast and a single presentation modality (A-V or A-O). The score was based on eight binary trials. Due to the small trial size, individual contrast scores were interpreted as pass/fail, given that only a score of seven or eight is significantly better than chance. Therefore, OlimSpac performance was determined by a composite score reflecting the average across all six contrasts, based on 48 binary trials. Average composite scores for both the A-V and A-O conditions were lower, albeit not significant, for young children with cochlear implants compared to their articulation-matched controls. Examination of individual phonemic contrast scores revealed that the articulation-matched sample of normal hearing participants most often failed the post-alveolar consonant place contrast, whereas children with cochlear implants most often failed the consonant voicing contrast. There were also no significant within group difference in speech perception performance between the A-V and A-O conditions of the OlimSpac. The results of this study demonstrated that children with cochlear implants achieved similar speech perception performance to their articulation-matched normal hearing peers. Although children's speech production abilities partially influenced their OlimSpac performance, knowledge of word-level articulation skills allows clinicians to make appropriate judgments when interpreting composite scores, thus validating the OlimSpac as an indirect measure of a child's speech perception capacity and a direct measure of speech perception skills. Objective scores obtained from a child's OlimSpac performance may be used to assess outcomes of cochlear implant use, guide cochlear implant mapping, and plan habilitative intervention. A greater understanding of the potential effect of speech production performance on estimates of speech perception ability may also assist in highlighting other developmental, linguistic and/or cognitive delays masked by a child's hearing loss.

published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology

published_or_final_version / abstract / toc / Speech and Hearing Sciences / Master / Master of Science in Audiology

published_or_final_version / abstract / toc / Speech and Hearing Sciences / Master / Master of Science in Audiology

published_or_final_version / abstract / toc / Speech and Hearing Sciences / Master / Master of Science in Audiology