Background: Distortion product otoacoustic emissions (DPOAEs) are a promising screening technique for the early detection of subtle noise induced cochlear function changes. Objectives: To determine the applicability of DPOAEs as a health surveillance technique for the early detection of noise induced hearing loss (NIHL) in workers at a steel manufacturing industry. Methods: DPOAEs were recorded in 20 participants with no history of occupational noise exposure and 20 participants exposed to noise in the steel manufacturing industry. Participants were not exposed to noise for at least 48 hours prior to testing. All participants were male with normal audiometric thresholds of ?15 dB HL. The DPOAE presence and response amplitude levels for different frequencies were compared between the two groups. The study further evaluated the short-term test-retest repeatability of DPOAE measurements, and also compared the total test duration of performing DPOAEs to the duration of screening audiometry. Results: The noise exposed group had statistically significantly lower DPOAE response amplitudes than the control group for all the tested frequencies; (p&#0600.001) at 2002 to 4004 Hz, and (p=0.01, p=0.001) at 6348 and 7996 Hz respectively, suggesting more cochlear damage in the noise exposed group due to early outer hair cell damage. DPOAEs showed very good reproducibility, and the average duration of performing a set of DPOAEs was significantly shorter (461 ± 68.2 seconds) than the duration of performing audiometry (591 ± 76.9 seconds), p&#0600.001. Conclusion: DPOAEs appeared to be a sensitive technique in detecting noise induced subtle cochlear function changes. DPOAEs could be used as a health surveillance technique for the early detection of NIHL in the steel manufacturing industry. / Dissertation (M Communication Pathology)--University of Pretoria, 2016. / Speech-Language Pathology and Audiology / M Communication Pathology / Unrestricted

The purpose of this study was to investigate further the characteristics of hearing loss in ventriculoperitoneal (VP) shunted hydrocephalus. Twelve (VP) shunt treated hydrocephalus children participated in this study. The etiology of the hydrocephalus was either intraventricular hemorrhage or spina bifida. A recent neurological examination reported the shunt to be patent in each child. Audiometric examination included pure tone air conduction thresholds, tympanometry, contralateral and ipsilateral acoustic reflex thresholds and distortion product otoacoustic emissions (DPOAEʹs). A unilateral, high frequency, sensorineural hearing loss was found in the ear ipsilateral to shunt placement in 10 (83%) of the 12 shunt treated hydrocephalic children. No hearing loss was observed the ear contralateral to shunt placement. Based on the pure tone findings coupled with the decrease in DPOAE amplitude in the shunt ear, the hearing loss appears to be cochlear in nature. It is hypothesized that the cochlear hydrodynamics are disrupted as the result of fluid pressure reduction within the perilymph being transmitted via a patent cochlear aqueduct as a reaction to the reduction of CSF via a patent shunt. In addition, a concomitant brainstem involvement is evidenced in the ART pattern possibly produced by the paten shunt draining CSF from the subdural space resulting in cranial base hypoplasia.

This paper provides an overview of developmental timetables relevant to hearing and of current pediatric audiological techniques and practices. The first sections summarize structural and functional development of the auditory pathway and the development of primary auditory processing. These developmental sequences appear to follow similar paths in humans and animals. Speech and music perception involve more complex processing and are strongly influenced by experience. Hearing disorders affect the perception of complex sounds in a variety of ways, depending on the site(s) of lesions. Early onset hearing impairment, including conductive loss from chronic otitis media, can seriously impede language development. Language cannot develop normally without adequate speech stimulation. Sensitive and inexpensive techniques are available for performing neonatal hearing screening, and early intervention has a positive effect on development of language skills in hearing-impaired children. Thus, the National Institute of Health has recommended nationwide universal newborns hearing screening. The rationale and methodology of universal screening programs is summarized in the chapter. Advances in the field of the genetics of hearing impairment are also reviewed Recent advances in the field of auditory physiology - coupled with longstanding concerns about delayed identification of hearing impairment - have precipitated public health initiatives (National Institute of Health, 1993) and legislation for neonatal hearing screening programs (Blake & Hall, 1990). Pediatric audiology, once more “art” than science, is now largely based on physiologic methods rather than observed behavior. With current techniques, it is not only possible to detect hearing impairment at birth but also to determine the site of the lesion and to obtain close estimates of hearing threshold at specific frequencies (Werner, Folsom, & Mancl, 1993). Habilitative measures, including amplification, can begin within weeks of birth. Protocols for the management of hearing impairment are guided not only by the site of the lesion but by the developmental sequences and interactions among all of the child’s sensory modalities. This chapter provides an overview of developmental timetables relevant to hearing and of current pediatric audiological techniques and practices.

Previous studies show that pure tone thresholds are strongly correlated with distortion product otoacoustic emission amplitudes when evaluating the frequency range from 1 to 8 kHz (Avan & Bonfils, 1993). Little is known about correlations between these two measures at higher frequencies from 9-16 kHz. This study compared pure tone thresholds and distortion product otoacoustic emissions (DPOAEs) in this high frequency range for 29 normal hearing subjects ages 18-30. Pure tone thresholds were obtained at 250-16 kHz and distortion product otoacoustic emissions (DPOAE) 2,211-17,675 were measured in the same ears. DPOAE amplitudes were measured using a constant F1/F2 ratio of 1.2, with F2 values ranging from 2,211-17,675 Hz. Data obtained from 50 ears showed a decline in DPOAE amplitude with increasing frequency of the F1 and F2 primary stimulus tones. Behavioral thresholds demonstrated an increase with increasing frequency of the pure tone stimulus. Pearson r-correlation analysis demonstrated a weak relationship between measures. Further investigation revealed that equipment variables prevented accurate readings.

No description available.

Die Modulation von Distorsionsprodukt-Otoemissionen (DPOAE) durch Töne tiefer Frequenz ist ein Methode, mit der die Auswirkung von Verlagerungen der kochleären Trennwand auf die Funktion des kochleären Verstärkers untersucht werden kann. Damit bietet sie einen neuen objektiven Ansatz zur Diagnostik unterschiedlicher kochleärer Hörstörungen sowie zur Untersuchung physiologischer Mechanismen der Kochlea. Durch einen tieffrequenten Ton (f = 32,8 Hz) werden die DPOAE in Abhängigkeit von dessen Phase periodisch verändert. Die Ausprägung der Modulation hängt von den Parametern des Tieftons und der Primärtöne (mit den Frequenzen f1 und f2) ab. Bei zwölf normalhörenden Probanden wird der Einfluß des Tieftonpegels, der Primärtonpegel und der Primärtonfrequenzen auf die Modulation der DPOAE mit der Frequenz 2f1-f2 untersucht. Die Ergebnisse dieser Methode werden mit denen der subjektiven Phasenaudiometrie bei diesen Probanden verglichen. Mit den Primärtonfrequenzen f1 = 2,5 und f2 = 3 kHz steigt die mittlere Modulationstiefe der DPOAE mit zunehmendem Tieftonpegel sowie mit abnehmenden Primärtonpegeln nichtlinear. Mit hohem Tieftonpegel (L = 115 dB SPL) und geringen Primärtonpegeln (bis zu L1 = 50 und L2 = 30 dB HL) sind DPOAE-Pegelverläufe mit zwei Minima und zwei Maxima pro Tieftonperiode zu beobachten. Die Pegelminima liegen kurz nach der maximalen Druck- bzw. Sogphase des Tieftons vor dem Trommelfell, entsprechend der maximalen Auslenkung der kochleären Trennwand in Richtung Scala vestibuli bzw. Scala tympani. Sie zeigen eine mittlere Latenz von 4 ms gegenüber den Verdeckungsmaxima der subjektiven Mithörschwelle im Phasenaudiogramm, die wahrscheinlich durch die Summe der Antwortzeit der aktiven kochleären Prozesse und der Laufzeit der DPOAE-Signale retrograd aus der Kochlea zur Meßsonde im äußeren Gehörgang zustande kommt. Mit geringeren Tieftonpegeln (L = 110 dB SPL) bzw. höheren Primärtonpegeln (ab L1 = 55 und L2 = 40 dB HL) sowie höheren Primärtonfrequenzen (f1 = 4, f2 = 4,8 kHz) sind nur noch jeweils ein DPOAE-Pegelminimum und -maximum pro Tieftonperiode zu beobachten. Mit den Primärtonfrequenzen f1 = 5 und f2 = 6 kHz zeigt sich keine Modulation der DPOAE mehr. Die Ergebnisse werden unter Verwendung einer Boltzmannfunktion zweiter Ordnung als Annäherung an die mechano-elektrische Transferfunktion äußerer Haarzellen simuliert. Bei einigen Probanden werden außerdem die Modulation der DPOAE mit der Frequenz 3f1-2f2 durch den tieffrequenten Ton sowie der Einfluß spontaner otoakustischer Emissionen (SOAE) auf die Messung tieftonmodulierter DPOAE untersucht. / Low-frequency modulation of distortion product otoacoustic emissions (DPOAE) is a method which allows to investigate the effect of the displacement of the cochlear partition on the function of the active cochlear process. It offers a new objective approach to diagnose different sensory hearing disorders as well as to investigate physiological cochlear mechanisms. The DPOAE are modulated by a low-frequency tone (with the frequency f = 32,8 Hz), depending on its phase. The extent of this modulation depends on the acoustic parameters of the suppressing low-frequency tone and the stimulating primary tones (f1 and f2). In twelve normal hearing subjects the influence of the low-frequency tone level, the levels and the frequencies of the primary tones on the modulation of the DPOAE with the frequency 2f1-f2 are investigated. In these subjects, the phase-dependent masked subjective threshold is also registered. The results of both methods are compared. With the primary tone frequencies f1 = 2,5 and f2 = 3 kHz the mean value of the DPOAE modulation depth presents a nonlinear growth with increasing low-frequency tone level and decreasing primary tone levels, respectively. With high low-frequency tone level (L = 115 dB SPL) and low primary tone levels (up to L1 = 55 and L2 = 40 dB HL), the time course of the DPOAE level shows two minima and two maxima within one period of the low-frequency tone. The minimal DPOAE levels are registered shortly after the phases of maximal condensation and rarefaction of the low-frequency tone in front of the eardrum, respectively, corresponding to the largest displacement of the cochlear partition towards the scala tympani and the scala vestibuli. The time course of the DPOAE level shows a mean latency of 4 ms with regard to the masking patterns of the phase-dependent masked threshold, due to the response time of the active cochlear process and the retrograde travelling time of the DPOAE. With lower low-frequency tone levels (L1 = 110 dB SPL), higher primary tone levels (from L1 = 55, L2 = 40 dB HL), and higher primary tone frequencies (f1 = 4, f2 = 4,8 kHz), respectively, the DPOAE level presents only one maximum and one minimum per period of the low-frequency tone. With the primary frequencies f1 = 5 and f2 = 6 kHz no modulation of the DPOAE is registered. The results are simulated using a second-order Boltzmann function as an approximation of the mechano-electric transfer function of the outer hair cells. Additionally, in some subjects the low-frequency modulation of the DPOAE with the frequency 3f1-2f2 and the influence of spontaneous otoacoustic emissions (SOAE) on the registration of low-frequency modulated DPOAE are investigated.

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

KwaZulu-Natal has been ranked as having the fourth highest incidence of transmitted Multiple Drug Resistant-Tuberculosis (MDR-TB) in sub-Saharan Africa. Substantial literature exists indicating the permanent damage that MDR-TB medication has on hearing abilities. The purpose of this study was to describe the hearing function of adults on long term MDR-TB treatment from Murchison Hospital MDR-TB unit in the Ugu District in rural KwaZulu-Natal. The primary aim of the study was to review the possible changes in hearing function in a group of adults on long-term treatment for MDR-TB. Secondly, the study aimed to estimate the number of adults who may present with changes following MDR-TB treatment and establish if relationships exist between the audiological findings and factors such as age and gender. The design of the study was a retrospective comparative data review of 68 patient records, all of which underwent audiological investigations from the start of MDR-TB treatment over a five-month period. The study made use of descriptive and inferential statistics to analyse the data. Specific inferential statistical analysis included analysis of covariance as well as regression analysis. Results from the study showed changes in hearing function in Distortion Product Otoacoustic Emissions (DPOAEs) and Pure Tone Audiometry (PTA) results at all five audiological sessions and across a range of frequencies. 84% of the total sample presented with overall refer readings for DPOAEs and 98.53% of the group of adults presented with criteria indicative of ototoxic hearing loss, specifically a bilateral mild-profound sloping SNHL on clinical PTA results. In the total sample of patient records reviewed in this study, all 68 records showed a change in hearing function, be that changes in DPOAE function and/or changes in PTA thresholds, following long-term treatment for MDR-TB. Variations in the effects of gender and ear difference were minimal and non-significant in all results. Similar presentation, to ototoxic hearing loss, of other degenerative conditions exists; however these conditions were accounted for as exclusion criteria in this study. Therefore the only remaining cause of possible hearing deficit was that of ototoxicity. The study provided valuable data regarding hearing function in a population of adults on long-term MDR-TB treatment in South Africa. Furthermore, the study has highlighted the need for the establishment of standardised audiological monitoring programmes sensitive to ototoxic hearing loss, within the South African context where the incidence of Tuberculosis (TB) and MDR-TB is reportedly high.

INTRODUÇÃO: O processamento da informação sonora depende da integridade das vias auditivas. O sistema auditivo eferente pode ser avaliado por meio de dois métodos objetivos e não-invasivos: a obtenção dos limiares dos reflexos acústicos, e a supressão das emissões otoacústicas. OBJETIVO: Verificar a atividade do sistema auditivo eferente, por meio da supressão das emissões otoacústicas por transientes (EOAT) e da sensibilização do reflexo acústico em indivíduos com alteração de processamento auditivo. MÉTODO: Foram avaliadas 50 crianças com alteração de processamento auditivo (grupo estudo) e 38 crianças sem alteração de processamento auditivo (grupo controle), por meio das EOAT evocadas por \"clicks\" na ausência e na presença de ruído ipsilateral e contralateral, e por \" tone bursts\", nas freqüências de 1000, 2000 e 4000 Hz na ausência e na presença de ruído contralateral, e de reflexo acústico nas freqüências de 500, 1000, 2000 e 4000 Hz na ausência e na presença de estímulo facilitador ipsi e contralateral. RESULTADOS: O valor da média de EOAT evocadas por \"clicks\" com estímulo supressor foi de até 1,50 dB para o grupo controle e de até 1,26 dB para o grupo estudo. Para as EOAT evocadas por \"tone bursts\" com estímulo supressor, os valores médios foram de até 2,69 dB para o grupo controle e de até 2,79 dB para o grupo estudo. Foi observado efeito de sensibilização do reflexo acústico com redução média de até 18,17 dB para o grupo estudo e de até 17,38 dB para o grupo controle. Não foi observada diferença estatisticamente significante entre as respostas do grupo controle e do grupo estudo, para supressão de EOAT (exceto na freqüência de 2000 Hz - \"tone burst\"), e para sensibilização do reflexo acústico. CONCLUSÕES: O grupo estudo apresentou valores reduzidos na pesquisa de supressão das EOAT e valores aumentados na sensibilização do reflexo acústico, em relação ao grupo controle. / INTRODUCTION: Auditory processing depends on the auditory pathways integrity. Efferent auditory system may be assessed in humans by two non-invasive and objective methods: acoustic reflex and otoacoustic emissions suppression. OBJECTIVE: Analyze efferent auditory system activity by otoacoustic emissions suppression and acoustic reflex sensitization in human subjects with auditory processing disorders. METHOD: Fifty children with auditory processing disorders (study group) and thirty-eight children without auditory processing disorders (control group) have being evaluated using clicks otoacoustic emission suppression with and without ipsilateral and contralateral white noise; tone bursts otoacoustic emission suppression in 1000, 2000 and 4000 Hz with and without contralateral white noise and acoustic reflex in 500, 1000, 2000 and 4000 Hz with and without ipsilateral and contralateral facilitator. RESULTS: The higher clicks otoacoustic emission suppression was up to 1.50 dB for the control group and up to 1.26 dB for the study group. The higher tone burst otoacoustic emission was up to 2.69 dB for the control group and up to 2.79 dB for the study group. The higher acoustical reflex sensitization was up to 18.17 dB for the study group and up to 17.38 dB for the control group. There was no significant statistical difference between results for control group and study group to otoacoustic emission suppression (except for 2000 Hz) and acoustical reflex sensitization. CONCLUSION: Study group presented smaller otoacoustic emission suppression than control group and study group presented higher acoustical reflex sensitization than control group.

Objetivo. Este estudo teve como objetivo analisar os resultados de um programa de triagem auditiva neonatal em recém-nascidos pré-termos de um hospital público do município de Itapetininga, Estado de São Paulo. Métodos. A triagem auditiva neonatal foi realizada em 230 neonatos com idade gestacional variando de 28 a 37 semanas, por meio do exame de emissão otoacústica evocada produto de distorção, utilizando-se o equipamento AUDX Biologics. Foram analisados os seguintes aspectos do programa: a) as condições operacionais da realização da triagem auditiva no hospital pesquisado; b) as características da prematuridade presentes na população estudada; c) os resultados do programa de triagem em relação à identificação de casos com alterações auditivas; d) as amplitudes médias de resposta da emissão otoacústica evocada produto de distorção encontradas na população avaliada. Resultados. Foram avaliados 90,55% dos prematuros nascidos num período de 15 meses de coleta. Verificou-se que as condições operacionais para a realização do programa foram adequadas. Não foram encontrados casos de alterações auditivas. As amplitudes médias de respostas da emissão otoacústica evocada produto de distorção (PD-RF) variaram de 11 a 17 dBNPS, nas freqüências de 2 a 5 kHz; tendo sido observadas respostas superiores para as orelhas direitas do sexo feminino. Conclusões. Os prematuros constituíram uma população de baixo risco para deficiência auditiva. As amplitudes de respostas da emissão otoacústica com equipamento portátil mostraram-se semelhantes às obtidas com equipamentos clínicos. O programa de triagem auditiva neonatal pode ser realizado no hospital estudado. Porém, modificações na rotina devem ser realizadas para que possa ser implantado um programa universal. / Objective. The aim of this paper is to analyze the results of a newborn hearing screening programme applied to preterm infants from the city of Itapetininga, state of São Paulo. Methods. Newborn hearing screening was performed to 230 preterm newborns with gestational age from 28 to 37 weeks. The equipment used was AUDX Biologics performing the registry of otoacoustic emissions distortion product. The presence of cocleopalpebral reflex was performed too. It were analyzed: a) operational conditions of newborn hearing screening programme; b) the characteristics of infant?s prematurity; c) incidence of hearing impairment; d) amplitude of otoacoustic emissions distortion product responses (PD-NR). Results. The operational conditions of newborn hearing screening are suitable. No hearing impairment was identified, probably because the prematurity characteristics had load this group to low risk for hearing loss. The mean values from amplitude (PD-NR) extended from 11 to 17 dBSPL from 2 to 5 kHz. They were observed superior values to right ears of the female group. Conclusions. Newborn?s characteristics of prematurity showed low risk for hearing impairment in this study. Portable equipment responses are similar to clinic ones. Newborn hearing screening programme is feasible to be implemented at that kind of hospital. However, some adjusts need to be done in order to extends it to the universal protocol.