The study of otoacoustic emissions (OAE) from the human ear is introduced with special reference to their clinical applicability. The need for a new instrument is demonstrated, which is capable of measuring click evoked OAEs in the clinical environment. Preparatory to the specification and construction of such an instrument, a thorough examination of the transient acoustic response of the ear canal, and the physical properties of the OAE was undertaken. An outcome of this research was the development of a technique which efficiently extracts the cochlear response component from that of the ear canal and middle ear. Various implementations of possible clinical OAE test systems were developed using a minicomputer prototype OAE instrument. A dedicated clinical OAE measurement instrument was designed and constructed to implement the findings of the above. This comprised 2 digital circuit boards and an extensive suite of software based around an IBM PC. Evaluation of the instrument was undertaken during the testing of patients attending the premises for auditory investigations. Operator experience of instrument function are discussed and used for further refinements. The instrument was placed in routine clinical service. Results for patients with a variety of hearing pathologies are discussed. The practical evaluation of the instrument highlighted two areas for further research. Experimental studies were undertaken to establish the role of the middle ear and the value of latency analysis on the OAE. The instrument developed during this project has been introduced into clinical/laboratory service internationally. A discussion of possible further developments of the instrument/technique are given.

Objective: This study aimed to examine the current available peer-reviewed evidence in order to gain insight into the most effective procedures used for the early identification and monitoring of aminoglycoside (AG)-induced cochleotoxicity and to suggest a protocol based on these findings. Method: Several databases were sourced with a comprehensive search conducted on Pubmed, Scopus and Medline (Ovid) to identify peer-reviewed studies published in English up until March 2020. The Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines were adhered to. Studies were subjected to pre-set inclusion and exclusion criteria in order to eliminate the possibility of effects other than AG/s influencing auditory functioning. The reference lists of the included studies were also screened. Results: Twenty-one studies met the inclusion criteria for the systematic review and were analysed. The majority of the studies used conventional pure tone audiometry (PTA) with only a few studies using extended high frequencies (EHF/s) and otoacoustic emission (OAE) testing. Conclusion: Since the damaging effect of AG/s is evident at the outer hair cells (OHC/s) of the basal end of the cochlea first, EHF audiometry and distortion product otoacoustic emissions (DPOAE/s) testing seems more promising for the early detection and monitoring of AG-induced cochleotoxicity. For effective and efficient identification and monitoring of AG-induced cochleotoxicity, a test battery comprising of a combination of subjective and objective measures, specifically aimed at the OHC/s by means of EHF audiometry and OAE-testing (DPOAE specifically) and possibly speech-in-noise (SPIN) tests such as the digits-in-noise (DIN) / SPIN-tests, is recommended as a standard protocol. / Dissertation (MA (Audiology))--University of Pretoria, 2020. / Speech-Language Pathology and Audiology / MA (Audiology) / Unrestricted

Background More than a billion adolescents and young adults are at risk of acquiring recreational noise-induced hearing loss (RNIHL) due to the unsafe use of Personal Audio Systems (PAS). Although preventable, once occurred the RNIHL is irreversible and can have a severe negative impact on physical and mental health as well as on academic or work performance. Educational programs alone have not been effective in changing listening behaviour in PAS users. Objectives The present study, therefore, aimed to determine (i) the accuracy and reliability of dbTrack (Westone) sound-level monitoring earphones and (ii) the effect of sound-level monitoring earphones with smartphone feedback and hearing health information as an intervention to promote healthy listening behaviours in young adults. Design The study consisted of two phases, the first phase investigated the accuracy and reliability of dbTrack sound-level monitoring earphones. Accuracy was determined by comparing earphone measurements to sound level meter measurements. Intra-device reliability was determined by comparing earphone measurements during test-retest conditions. Nineteen participants were recruited through convenience sampling to determine within-subject reliability by comparing in-ear sound levels measured by the earphones during test-retest conditions. For the second phase of the study, a single-group pretest-posttest design was utilized. Forty participants, recruited through snowball sampling, utilized dbTrack (Westone) sound-level monitoring earphones with the accompanying dbTrack smartphone application for 4 weeks. The application’s smartphone feedback was disabled during the first 2 weeks (pretest condition) and enabled during the last 2 weeks (posttest condition). Average daily intensities, durations and sound dosages measured during pre- and posttest conditions were compared. Results Phase 1 dbTrack earphone measurements were within 1 dB when compared to sound level meter measurements. Earphones were also within 1 dB in repeated measures across earphones and across participants. Phase 2 posttest average daily intensity decreased by 8.7 dBA (18.3 SD), duration decreased by 7.6 minutes (46.6 SD) and sound dose decreased by 4128.4% (24965.5% SD). Differences in intensity and sound dose were significantly lower with small and medium effect size, respectively. Conclusions This study’s data indicate that dbTrack (Westone) sound-level monitoring earphones with a calibrated in-ear microphone can reliably and accurately measure PAS sound exposure. Preliminary results also suggest that feedback on sound exposure using the accurate sound-level monitoring earphones with the accompanying dbTrack application can potentially promote safe listening behaviour in young adults and reduce the risk of acquiring an RNIHL. / Dissertation (MA (Audiology))--University of Pretoria, 2020. / Speech-Language Pathology and Audiology / MA (Audiology) / Unrestricted

Prescribing hearing technology (HT) to children with hearing loss is based on the expectation that it will improve auditory-based communication outcomes, literacy, occupational prospects, and psycho-social wellbeing. The desired effect, however, can only be achieved if appropriate HT is used optimally to foster consistent, cumulative auditory experiences comparable to peers with normal hearing. Therefore, a better understanding of the factors that influence HT use in children with hearing loss is necessary to guide hearing healthcare services and facilitate auditory-based outcomes. This study aimed to identify and describe predictors of daily HT use in children with hearing loss. A retrospective review of clinical records collected data, including demographic, family, intervention, socio-economic, audiology-related, and HT information. The study sample included 505 children (<11 years of age), fitted with hearing aids (HAs), cochlear implants (CIs), and bone conduction hearing devices (BCHDs), and enrolled in a South African auditory-oral intervention program between 2010 and 2018. Results demonstrated an average HT use of 9.4 hours a day for the entire sample. Multiple regression analyses were performed to identify predictor variables that influenced HT use. From the 42 variables included in the retrospective dataset, the bivariate analyses yielded 31 potential predictor factors. The final general linear model (GLM; p <.01, R2= 0.605) identified 10 interacting factors that were significantly associated with increased HT use in children. Intrinsic predictors of increased HT use included a more severe degree of hearing loss, older ages at diagnosis and initial HA fitting, and older chronological age. Extrinsic predictors included the child’s ability to independently use HT, at least one CI as part of the HT fitting, coordinated onsite audiological management, self-procured batteries, auditory-oral communication mode, and regular caregiver intervention attendance. Six of the 10 predictors identified were novel and previously undescribed in the literature, including CI recipiency, independent HT use, caregiver intervention attendance, older ages at diagnosis and initial HA fitting, and self-procured batteries. In conclusion, the average HT use for this study sample was high but below recommended all-day HT use. Although HT use is a multi-factorial outcome measure, an extensive range of predictive factors was identified that could predict and increase HT use in children. Additionally, four of the predictors, both novel and extrinsic, are malleable, signifying that intervention can change the outcome, namely HT use. These newly described predictors of HT use can contribute to evidence-based intervention services that promote optimal auditory-based outcomes. / Dissertation (MA (Audiology))--University of Pretoria, 2021. / Speech-Language Pathology and Audiology / MA (Audiology) / Unrestricted

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