Thesis (M.S.)--Brigham Young University. Dept. of Audiology and Speech-Language Pathology, 2006. / Includes bibliographical references (p. 31-34).

Thesis (B.Sc)--University of Hong Kong, 2002. / "A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), The University of Hong Kong, May 10, 2002." Also available in print.

Thesis (M. (Communication Pathology))--University of Pretoria, 2006. / Includes bibliographical references.

Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 2000. / This document gives a report on the research that has been done to simulate hearing loss. People working with the hearing impaired have no idea of what and/or how the hearing impaired person hears sound. An instrument that enables a normal hearing person to hear what a hearing impaired person hears, is referred to in this document as a Hearing Loss Simulator (HLS). An investigation of the feasibility and practicability of the abovementioned instrument, has led to the development of the HLS by making use of a distinct type of technology called Digital Signal Processing (DSP) technology. Before hearing loss can be simulated, the hearing loss first needs to be determined. A study of different procedures and methods for screening hearing has led to the incorporation of an existing instrument called an Audiometer. An audiometer is an instrument that determines the hearing loss by making use of pure tone sine waves. The results are then plotted on a graph called an Audiogram. The results of other methods that determine the hearing loss can also be transferred to the Audiogram. The Audiogram's information which is, in fact, the frequency response of the ear, is stored in a computer and is utilized to realize the HLS function. Six different DSP based methods were studied to shape any audio information according to a specific frequency response. The optimum method was identified and then implemented. The various methods are the following: Filter bank method Inverse Discrete Fourier Transforms (IDFT) method Inverse Fast Fourier Transforms (IFFT) method Chirp-z method Wavelet method Yule-walker method The ITFT method was identified as the optimum method and was therefore implemented. The algorithm to realize this method, was carried out by doing the IFFT calculation on computer and subsequently doing the filtering on a DSP processor called an ADSP-2181 processor. The audio information under investigation is fed into the instrument, it is then filtered according to the audiogram information and then sent out again. Any normal hearing person who wants to investigate the hearing impairment of the hearing impaired person can listen to sound reproduction through either a set of headphones or through a free field. This process is referred to in this dissertation as Hearing Loss Simulation. / Foundation of Research and Development

No description available.

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

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

Nineteen normal-hearing university undergraduates performed an "objective" and a "subjective" test of speech intelligibility accuracy (SIA), speed (SIS) and ease (SIE) for different levels of low-pass filtered speech. During objective testing subjects listened to monosyllabic words low-pass filtered through an earphone, and repeated words as correctly and quickly as possible. They simultaneously turned off a probe light as quickly as possible whenever it appeared. Objective SIA was assessed as percentage of incorrectly-repeated phonemes, objective SIS as elapsed time between word presentation and a subject's voice response, and objective SIE as probe-reaction time to turning off the light. During subjective testing subjects listened to common sentences low-pass filtered through a loudspeaker in a background of competing speech. Subjective SIA, SIS and SIE were assessed using magnitude estimation in which subjects assigned numbers to how accurately, quickly or easily they understood the sentences. The most important finding was generally improved accuracy, speed and ease of objectively- and subjectively-measured speech intelligibility with decreased filtering. The experimenter further analyzed results by determining how well each measure of SIA, SIS and SIE met assumptions of test sensitivity, selectivity, reliability, convergence, discriminability and sufficiency. Overall, the objective SIA measure best met assumptions, followed by the three subjective measures, the objective SIS measure, and the objective SIE measure. Results have clinical and research implications for testing and understanding normal and impaired speech intelligibility and perception. First, results are encouraging for audiologists who use objective SIA and subjective measures to test speech intelligibility of their patients. Second, results suggest that persons listening to degraded speech, or persons with auditory problems, may have difficulties in SIS and SIE as well as problems already documented for SIA. Accordingly, audiologists should consider SIS and SIE during audiologic evaluations, aural rehabilitation, and auditory research. Finally, a few subjects showed exceptionally fast voice-response and probe-reaction times which has implications for understanding the nature and limits of human auditory processing.

The purpose of this study is to determine if significant audio-metric characteristics exist in individuals having cochlear lesions who trace a Bekesy pattern characteristic of individuals with normal hearing or conductive losses.

There is a higher prevalence of hearing loss in children with diagnosed neurological disorders than the general paediatric population. It is therefore essential that these children have their hearing assessed. Conventional behavioural audiometry requires participation from the child, and in a majority of this population with neurological pathology this is not always possible owing to their neurocompromised state. These children will have to undergo objective testing, such as the Auditory Brainstem Response (ABR) in order to obtain estimated hearing thresholds, as this requires no active involvement from the patient. This study therefore aims to describe the audiological ABR findings in order to determine hearing function in this group and to establish a relationship between audiological ABR findings to behavioural audiometry findings where these exist in a group of neurologically disordered children in a tertiary hospital in South Africa. Methods: A retrospective review was conducted on 40 ABR patient records of children between the ages of 5 months and 10 years diagnosed with a neurological disorder. Behavioural audiometry results were then sought for these children, where these existed. Hearing status was described for each child per ear for both objective and behavioural results, and descriptive statistics were conducted. Results: 56.25 % (n=45) of ears in this study presented with normal hearing on ABR testing. No behavioural audiometry results were obtained in 72.5 % (n=58) of ears in this study. Results correlated between ABR and behavioural testing for only 7.5% (n=8) of ears tested and in all eight of these ears the hearing result was within normal hearing limits. Twelve and a half percent (n=10) of ears were misdiagnosed on behavioural testing. More premature infants were able to be tested behaviourally when compared to other pathologies. Cerebral palsy, Down’s Syndrome, prematurity and RVD were the pathologies in which the most hearing losses were diagnosed. Conclusions: Behavioural audiometry appears a largely unreliable method of hearing testing in children diagnosed with neurological disorders as results were obtained in only 27.5 % of the study sample; however it remains the gold standard in paediatric hearing testing in order to evaluate the entire auditory system and provides information on how a child processes sound, unlike ABR testing which only provides hearing information up to the auditory brainstem. This study highlights the high prevalence of hearing problems in children with neurological disorders and therefore the importance of hearing testing in this population. Hearing thresholds should be established for subsequent remediation via objective testing. Conditioning should continue simultaneously for a behavioural audiological test battery with adaptations for the child’s developmental ability.