Aim : The purpose of this study was to examine the impact of simulated hearing loss on the acoustic contrasts between declarative questions and declarative statements and on the perception of speech intonation. A further purpose of the study was to investigate whether any such effects are universal or language specific. Method: Speakers included four native speakers of English and four native speakers of Mandarin and Taiwanese, with two female and two male adults in each group. Listeners included ten native English and ten native speakers of Mandarin and Taiwanese, with five female and five male adults in each group. All participants were aged between 19 and 55 years old. The speaker groups were asked to read a list of 28 phrases, with each phrase expressed as a declarative statement or a declarative question separately. These phrases were then filtered through six types of simulated hearing loss configurations, including three levels of temporal jittering for simulating a loss in neural synchrony, a high level of temporal jittering in combination with a high-pass or a low-pass filter that simulate falling and rising audiometric hearing loss configurations, and a vocoder processing procedure to simulate cochlear implant processing. A selection of acoustic measures was derived from the sentences and from some embedded vowels, including /i/, /a/, and /u/. The listener groups were asked to listen to the tokens in their native language and indicate if they heard a statement or a question. Results: The maximum fundamental frequency (F0) of the last syllable (MaxF0-last) and the maximum F0 of the remaining sentence segment (MaxF0-rest) were found to be consistently higher in declarative questions than in declarative statements. The percent jitter measure was found to worsen with simulated hearing loss as the level of temporal jittering increased. The vocoder-processed signals showed the highest percent jitter measure and the spread of spectral energy around the dominant pitch. Results from the perceptual data showed that participants in all three groups performed significantly worse with vocoder-processed tokens compared to the original tokens. Tokens with temporal jitter alone did not result in significantly worse perceptual results. Perceptual results from the Taiwanese group were significantly worse than the English group under the two filtered conditions. Mandarin listeners performed significantly worse with the neutral tone on the last syllable, and Taiwanese listeners performed significantly worse with the rising tone on the last syllable. Perception of male intonation was worse than female intonation with temporal jitter and high-pass filtering, and perception of female intonation was worse than male intonation with most temporal jittering conditions, including the temporal jitter and low-pass filtering condition. Conclusion: A rise in pitch for the whole sentence, as well as that in the final syllable, was identified as the main acoustic marker of declarative questions in all of the three languages tested. Perception of intonation was significantly reduced by vocoder processing, but not by temporal jitter alone. Under certain simulated hearing loss conditions, perception of intonation was found to be significantly affected by language, lexical tone, and speaker gender.

Loudness recruitment is an abnormally rapid growth of perceived loudness above the hearing threshold that slows to normal growth as the intensity of the signal increases. Recruitment is common in sensorineural hearing loss and in simulated hearing loss with noise masking. This study looked at possible differences in loudness recruitment with age, noise level, and frequency. Participants from two age groups were tested. Group A included participants aged 18 to 30 years and Group B included participants aged 50 to 75 years. Participants practiced the Alternate Binaural Loudness Balance (ABLB) test without noise present. They then repeated the tests with masking noise. Tests were completed with two different noise levels (50 dB SPL and 70 dB SPL), and two different test tone frequencies (1000 Hz and 2000 Hz). Participants identified loudness matching points to reference intensities of 20, 40, 60, and 80 dB HL. Participants completed 3 trials at each intensity level. Difference scores of the intensity of the loudness matching point minus the intensity of the reference tone were computed and analyzed statistically. An analysis of variance (ANOVA) for repeated measures fails to show significance for between-subjects effect for age, within subject effect for frequency, and trial. An ANOVA for repeated measures shows significant within subject effect for noise and for intensity. The 70 dB SPL noise level shows greater difference scores and a steeper loudness matching function slope than the 50 dB SPL noise level. The greater difference scores and steeper slope are expected due to the higher hearing threshold created with the higher noise level. As the intensity level increases, the difference score decreases. The decrease in difference scores with increasing intensity levels shows the presence of loudness recruitment. The results of this study suggest the use of masking noise in order to measure recruitment is an acceptable simulation. Age alone does not account for changes in loudness recruitment. Therefore, recruitment measurement with noise masking may be a potential marker of early auditory dysfunction.

Speech audiometry is considered an essential tool in the assessment of hearing, not only to validate pure tone measurements, but also to indicate speech perception as a critical communicative function. The use of sentence material in the assessment of speech perception has great value as it simulates – more closely than single words – the type of speech stimuli that listeners are confronted with on a daily basis. In South Africa, speech recognition (reception and discrimination) abilities are most commonly assessed through the use of single words, presented by monitored live voice, a practice sternly criticized in the literature. Furthermore, speech recognition is commonly evaluated in an ideal (quiet) listening environment. This method gives an incomplete impression of a patient’s auditory performance, since everyday listening situations are often characterised by the presence of background noise that influences comprehension of speech. The present study was therefore launched with the aim to develop a reliable measure of speech recognition in noise using Afrikaans sentence material. The development of the test was conducted in three phases. The first phase entailed the compilation of culturally valid, pre-recorded Afrikaans sentence material. During the second phase the uniformity of the recorded sentence collection was improved by determining the intelligibility of each sentence in the presence of noise and eliminating sentences that were not of equivalent difficulty in this regard. The objective of the third phase was to arrange the sentence material into lists using two different methods of list compilation. The first method involved grouping sentences together based solely on their intelligibility in noise (as assessed in the previous phase). The second method was the well-documented method of compiling phonetically balanced lists. The inter-list reliability of both sets of lists was evaluated in both normal hearing listeners and listeners with a simulated high frequency hearing loss. The results provided valuable information on the process of developing a test of speech recognition in noise, especially in terms of options for list compilation. Findings indicated that lists compiled according to intelligibility in noise showed a higher degree of equivalence than phonetically balanced lists when applied to normally hearing listeners. However, when applied to listeners with a simulated loss, phonetically balanced lists displayed greater equivalence. The developed test provides a means of assessing speech recognition in noise in Afrikaans, and shows potential for application in the assessment of hearing impaired populations, individuals with auditory processing difficulties, and the paediatric population. In addition, the methodology described for the development of the test could provide a valuable guideline for future researchers looking to develop similar tests in other languages. / Dissertation (MCommunication Pathology)--University of Pretoria, 2008. / Speech-Language Pathology and Audiology / MCommunication Pathology / Unrestricted