Distortion product otoacoustic emissions (DPOAEs) arise within the cochlea in response to two stimulus tones (f1 and f2) at frequencies such as 2f1 − f2 and 2f2 − f1. Each DPOAE derives from two contributing mechanisms within the cochlea: a distributed distortion source and a reflection source. They are used for hearing screening, but a better understanding of their cochlear origin and transmission could potentially extend their clinical application to facilitate objective hearing loss assessment, differential diagnosis of sensorineural hearing losses and improved auditory rehabilitation using hearing aids. In this thesis a numerical model of the human cochlea is developed to study the generation of DPOAEs. It is based on a pre-existing active nonlinear model, the micromechanics of which are carefully re-tuned to simulate the response of the human cochlea to single- and two- tone stimulation. Particular attention is paid to the form and position of the nonlinearity within the model to best match experimental results. The model is also reformulated to verify its stability and ensure computational convergence of the iterative frequency domain solution method. Its predictions are validated against estimated time domain simulations and documented experimental DPOAE measurements. Additionally a novel method is developed for decomposing each frequency component of the cochlear response into forward and backward travelling waves, which is applied to investigate the multiple sources of both the 2f1 − f2 and 2f2 − f1 DPOAEs. The model is used to explain and predict a variety of phenomena observed in experimental DPOAE studies. It also confirms for the 2f1 − f2 emission, that the two source mechanisms are spatially separated and that the only significant reflection contribution is associated with the 2f1 − f2 travelling wave. In contrast, it predicts that the two source mechanisms will overlap in the case of the 2f2 − f1 DPOAE, which can be influenced by reflection of both the primary and 2f2 − f1 travelling waves.

No description available.

Normal-hearing adults have no difficulty in recognising consonants accurately, even in moderately adverse listening conditions. By contrast, users of multichannel cochlear implants have difficulty with the accurate perception of consonants, even in good listening conditions. Cochlear implant users are known to show systematic deficits in recognition of consonant features, with perception of the place feature, which relies on spectral information, being worst. These deficits may be attributed both to signal distortions introduced by the processing of the implants and to other factors, in particular the spectrotemporal distortions which occur at the interface between electrode array and auditory nervous system, including cross-channel interaction. The objective of the work reported here was to attempt to partial out the relative contribution of these different factors to consonant recognition. This was achieved by comparing cochlear implant users’ perceptual errors, analysed in terms of information transmission, with errors made by normal-hearing subjects listening to acoustic models of implant processing, in various conditions. Two initial experiments were undertaken to develop and refine an acoustic model of the Nucleus 24 cochlear implant. Findings from these two experiments informed the design of the main acoustic model experiment, which was undertaken in parallel with a further experiment involving users of the Nucleus 24 device. In both experiments, subjects listened to nonsense syllables with and without the addition of stationary background noise, in three different configurations of implant processing parameters. Additionally, in the acoustic model experiment, a simulation of cross-channel spread of excitation, or “channel interaction”, was varied. Results showed that acoustic model experiments were predictive of the pattern of consonant feature transmission in cochlear implant users with better baseline consonant recognition scores. Deficits in consonant recognition in this subgroup could be explained by the loss of phonemically relevant acoustic information in speech due to the nature of cochlear implant processing, while channel interaction appeared to play a smaller role in accounting for problems in consonant recognition. The work also evaluated the effect of changes in channel number and stimulation rate and failed to find any changes in consonant recognition as these parameters were varied. The lack of a stimulation rate effect was consistent with acoustic measurements of the temporal modulation transfer function of the processor, which showed almost no change across stimulation rates.

No description available.

It has been argued that apparent masking-level differences (MLDs) in users of bilateral bone-anchored hearing aids (BAHAs) provide evidence of binaural hearing. However, there is considerably less acoustical isolation between the two ears with bone conduction (BC) compared to air conduction (AC). The apparent MLDs may have arisen, at least in part, from inter-cranial interference between signals arising from the two BAHAs (i.e. monaural effect). That might also explain some of the inter-individual variation in both the magnitude and the direction of the MLDs reported in BAHA users. The present study was composed of three experimental stages with the main aim to investigate the influence of interference in normal hearing participants by measuring masking level difference in AC and BC to explore the conditions contributing to the reported variation. An additional aim was to investigate the performance of a newly designed BC transducer; the balanced electromagnetic separation transducer (BEST), for bone conduction research as well as more general clinical use. Stage 1 evaluated the performance of the BEST in comparison to the clinically used RadioEar B71 in a series of acoustical (sensitivity and harmonic distortion) and psychoacoustical (hearing thresholds and vibrotactile thresholds) measurements. The results from these studies led to the use of the BEST in the second and third stages because they produced significantly lower harmonic distortion at low frequencies (mainly 250 Hz). The psychoacoustic measurements alluded to the need to use different calibration values with the BESTs. Stage 2 was a preliminary investigation comparing the MLDs with standard bilateral configurations between the AC and BC in nine normal-hearing participants. Signals were pure tones at one of three frequencies (250, 500, 1000 Hz), presented via AC or BC. Broadband noise (100- 5000 Hz) was always presented via AC at 70 dB SPL. Thresholds were estimated using a three-alternative forced choice procedure combined with an adaptive staircase. Transducers used were insert earphones and the BESTs for BC testing. The results from this stage showed a statistical significant difference between AC and BC MLDs at 250, 500 and 1000 Hz (mean difference is 9.4, 6.6 and 3.5 dB respectively). Evidence of the change in the MLDs direction is observed at 250 Hz in three participants. Stage 3 consisted of the investigation of inter-cranial interference in eighteen normal hearing participants. This stage was composed of three main measurements. The first measurement compared the AC and BC MLDs at three test frequencies. The second measurement evaluated the transcranial attenuation (TA). The third measurement was the novel feature of the study it evaluated the monaural interference effect through the measurement of the diotic and dichotic conditions in one test ear. A significant discrepancy was found between the AC and BC MLDs of approximately 6, 1.5 and 2.5 dB at 500, 1000 and 2000 Hz, respectively. The TA was found to be lower than 10 dB at the three test frequencies. Measurable MTLDs were reported in some of the participants, high inter-subject variability was observed in the direction of the MTLDs. The BEST can reliably replace the B71 in clinical setup. Formal adjustment of the reference equivalent threshold force levels is advised. Binaural hearing was achieved through bilateral BC stimulation to a lesser magnitude compared to AC MLDs in normal hearing participants. The discrepancy between the AC and BC MLDs was reduced with the increase in the frequency. The discrepancy can partially be explained by the cross-talk of the signal in one ear. The results showed that in some participants the magnitude of the monaural tone level difference was similar to the magnitude of the BC MLD. Further investigation is recommended to investigate the association of the transcranial delay with the discrepancy between the AC and BC MLDs. This investigation also recommends the investigation of the AC and BC MLDs in patients fitted with bilateral BAHAs.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2015-06-16T14:06:04Z No. of bitstreams: 1 Cibele Gomes Bicalho Avaliação...2015.pdf: 1225744 bytes, checksum: 0e4067d0336141afabfd635be5750ec5 (MD5) / Approved for entry into archive by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2015-06-16T14:06:14Z (GMT) No. of bitstreams: 1 Cibele Gomes Bicalho Avaliação...2015.pdf: 1225744 bytes, checksum: 0e4067d0336141afabfd635be5750ec5 (MD5) / Made available in DSpace on 2015-06-16T14:06:15Z (GMT). No. of bitstreams: 1 Cibele Gomes Bicalho Avaliação...2015.pdf: 1225744 bytes, checksum: 0e4067d0336141afabfd635be5750ec5 (MD5) Previous issue date: 2015 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, Brasil / Introdução: Mucopolissacaridose (MPS) é um conjunto de doenças raras causadas pela deficiência de enzimas lisossômicas levando ao acúmulo de glicosaminoglicanos (GAG) em órgãos e tecidos, responsáveis pelo quadro clínico multissistêmico, crônico e progressivo. O comprometimento auditivo é frequente. Objetivo: Avaliar manifestações auditivas de pacientes com MPS. Metodologia: Estudo descritivo, série de casos do comprometimento auditivo de pacientes com MPS. Foi realizada avaliação retrospectiva através de revisão de prontuário e avaliação prospectiva de dezembro de 2012 a outubro de 2014. Foram analisados a primeira e a última avaliação otorrinolaringológica (ORL) e audiológica realizada. Resultados: A principal queixa auditiva foi a hipoacusia. Aperdaauditiva estava presente em quase todos os pacientes, sendo que a perda auditiva condutiva foi a mais frequente, especialmente nos pacientes com MPS VI. Conclusão: A perda auditiva é muito frequente em pacientes com MPS, devendo o acompanhamento audiológicoser realizado precocemente. / Introduction: Mucopolysaccharidosis (MPS) is a set of rare diseases caused by deficiency of lysosomal enzymes leading to accumulation of glicosaminoglicanos (GAG) in tissues and organs responsible for the multisystemic clinical, chronic and progressive symptons. Objective: Todescribe the profile of otorhinolaryngological clinical examination and audiology tests of patients with MPS disease. Methods:Study of case series. The evaluation was performed, at the beginning, in 31 patients with MPS I, II, IIIA, IV and VI. Results: The most common hearing complaint was hearing loss and it was confirmed by audiology tests in almost 100% of patients, mostly with condutive hearing loss. Conclusions: It is important to evaluate the complaints, physical examination and audiology tests in MPS disease. Otorhinolaryngologist should be part of professional group that follow these patients in order to better monitor their hearing and provide early hearing rehabilitation.

Antalet äldre personer med hörselnedsättning som lever inom äldreomsorgen i Sverige är stort. Av den anledningen är det viktigt att personalen inom äldreomsorgen innehar kunskap om hörsel och hörselrelaterade angelägenheter. Syftet med föreliggande studie var att undersöka vilken kännedom undersköterskor på vårdbostäder inom Örebro kommun har om hörsel och hörselnedsättning hos äldre samt deras kännedom om hörhjälpmedel och kommunikation med äldre personer som har hörselnedsättning. Studien avgränsades till att endast inkludera yrkesgruppen undersköterskor. Materialet i undersökningen bestod av en enkät som delades ut till 60 undersköterskor på sex olika vårdbostäder i kommunen. Studiens resultat visade att undersköterskorna hade viss bristande kännedom inom undersökningens tre huvudområden. Störst kännedom hade undersköterskorna om kommunikation, minst kännedom hade de om hörsel och hörselnedsättning. Trots att viss kännedom fanns bland undersköterskorna uppgav en betydande majoritet att de skulle ha nytta av ett skriftligt material som belyser de tre huvudområdena.

Syftet med denna litteraturstudie var att sammanfatta vetenskapligt dokumenterade resultat kring vilka psykologiska, sociala och psykosociala konsekvenser som tinnitus kan orsaka. Elva artiklar, tre kvalitativa och åtta kvantitativa, valdes ut vid litteratursökningen och analyserades. Analysen resulterade i tre resultatdelar, primära konsekvenser där psykologiska konsekvenser sorterades in, sekundära konsekvenser där sociala konsekvenser sorterades in och en för psykosociala konsekvenser. Den primära resultatdelen visade att personer med svår tinnitus ofta led av koncentrationsproblem, sömnproblem och psykologiska problem som exempelvis depressioner. Den sekundära resultatdelen visade att personer med svår tinnitus fungerade sämre i det sociala livet och undvek aktiviteter, jämfört med en population som inte har tinnitus. De psykosociala konsekvenserna som fanns dokumenterade var få. En artikel avvek från de övriga och visade liten påverkan på alla områden. Detta togs upp i diskussionen då artikelns författare ansåg att demografiska och kulturella faktorer kunde ha en positiv inverkan. Detta befanns vara intressanta faktorer som liksom hela det psykosociala området kräver ytterligare forskning. I diskussionen påpekades även att man inte kan fastställa om de psykologiska problemen har kommit som en biverkan av tinnitus eller var närvarande innan.

No description available.

<p>Acute otitis media (AOM) is a common disease in childhood and is one of the most common causes for outpatient antibiotic treatment. The major aetiological agents of AOM have varied over the decades. Now the three most common pathogens are <i>Streptococcus pneumoniae</i>, <i>Haemophilus influenzae</i> and <i>Moraxella catarrhalis</i>. The resistance patterns of these organisms have also varied from the beginning of the antibiotic era to the situation we have today with an increasing incidence of penicillin-resistant <i>S. pneumoniae</i> and a moderate to high frequency of beta-lactamase production in <i>H. influenzae</i> and <i>M. catarrhalis</i>. In Sweden we have continued to use the Scandinavian treatment policy of penicillins as the first-line antibiotic treatment of AOM, which has been implemented with good results in the past. The question is if this policy will continue to have acceptable treatment results.</p><p>In order to investigate aspects of treatment, protection and structural changes in AOM, an animal model was used.</p><p>Amoxicillin treatment of AOM caused by <i>H. influenzae</i> was studied. Amoxicillin treatment was shown to shorten the duration of the infection and to reduce the morphological changes normally observed after an untreated AOM. The influence of antibiotic treatment on recurrent AOM was evaluated. Amoxicillin treatment did not lead to less protection against reinfection. Abstaining from antibiotics did not improve the levels of serum IgG antibodies. The IgG levels were significantly higher in treated animals after rechallenge. AOM caused by <i>H</i>. <i>influenzae</i> with a non-beta-lactamase-mediated resistance to beta-lactams was investigated and it was observed that during amoxicillin treatment the chromosomal changes mediating resistance were possibly advantageous for the bacterium. In cultures from children with AOM, there is sometimes growth of several bacteria. The possibility of a sheltering effect of beta-lactamase-producing <i>H. influenzae</i> on a penicillin-sensitive <i>S. pneumoniae</i> in a mixed infection was investigated, and amoxicillin was shown to eradicate the pneumococci from the middle ear despite the presence of beta-lactamase. An increasingly cultured bacterium in nasopharynx and in AOM is <i>M. catarrhalis</i>. It is now beta-lactamase-producing in almost 100% of cases and is thus not eradicated by penicillins. An animal model of AOM caused by beta-lactamase-producing <i>M. catarrhalis</i> was established to study the course of this infection with the possibility of evaluating aspects of virulence between AOM pathogens. The AOM observed was a self-limiting disease.</p><p>The results obtained in this study in a rat model support the continuing use of penicillins as first-line drugs in the treatment of AOM. Penicillins are not sufficient to treat all causative agents, but the majority of pathogens including the most virulent bacteria are eradicated from the middle ear. </p>