Background: Some patients with chronic middle ear disease and multiple failed revisions, who also need a hearing aid, may benefit from an active middle ear implant. An advantage of an active middle ear implant is that the ear canal is unoccluded. Methods: Following extensive experimental development in temporal bones and investigations of various locations and attachments of a Vibrant Soundbridge transducer, a new titanium clip holder for the vibrant floating mass transducer was developed. This assembly is a total ossicular replacement prosthesis (TORP) that is placed on the stapes footplate. Six patients were implanted with this device. Results: Acoustic results demonstrate significantly improved gain, especially in the high frequencies, which is typically unobtainable by conventional hearing aids. Conclusion: The simple procedure of placing an active TORP assembly on the stapes footplate, similar to the implantation of a passive TORP prosthesis during tympanoplasty, offers promising treatment for cases of incurable middle ear disease. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

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

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

<p>This thesis addresses the biomechanics of the human middle ear, that part of the auditory system which converts sound pressure waves in air to fluid pressure waves in the cochlea. The middle ear's mechanism is analysed in four papers, three main and one supporting; in the main papers the middle ear is treated as a multi-particle, multi-rigid body ensemble possessing a variable number of degrees of freedom depending upon the case being investigated.</p><p>It is confirmed, using the standard representation of a single fused incudo-malleal block, that the middle ear's motion is linear, but when this fused block restriction is lifted nonlinearity is present which significantly affects the mechanism's behaviour. In view of the linearity of the chain under the fused block conditions, the explanatory veracity of the conventionally accepted `fixed axis hypothesis' of ossicular motion is examined and found to be wanting as a realistic description of the chain's physical movement.</p><p>The nonlinear behaviour of the ossicular chain centres around the action of the incudo-malleal joint. This joint is shown to have preferential planes of operation, principally the pitch or longitudinal plane and in general to act as an efficient energy dissipator at high driving pressures and low frequencies. Providing the pressure is high enough, it is shown this energy dissipator effect eventually becomes independent of frequency.</p><p>The supporting paper discusses the dynamics of the imposition and removal of equation constraints justifying methods used to investigate the functioning of the incudo-malleal joint.</p>

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This thesis is part of an ongoing larger scale research study started in 2004 at the Naval Postgraduate School (NPS) which aims to develop a speech-driven human-machine interface for the operation of semi-autonomous military robots in noisy operational environments. Earlier work included collecting a small database of isolated word utterances of seven words from 20 adult subjects using an in-ear microphone. The research conducted here develops a speaker-independent isolated word recognizer from these acoustic signals based on a discrete-observation Hidden Markov Model (HMM). The study implements the HMM-based isolated word recognizer in three steps. The first step performs the endpoint detection and speech segmentation by using short-term temporal analysis. The second step includes speech feature extraction using static and dynamic MFCC parameters and vector quantization of continuous-valued speech features. Finally, the last step involves the discrete-observation HMM-based classifier for isolated word recognition. Experimental results show the average classification performance around 92.77%. The most significant result of this study is that the acoustic signals originating from speech organs and collected within the external ear canal via the in-ear microphone can be used for isolated word recognition. The second dataset collected under low signal-to-noise ratio conditions with additive noise results in 79% recognition accuracy in the HMM-based classifier. We also compared the classification results of the data collected within the ear canal and outside the mouth via the same microphone. The second dataset collected under low signal-to-noise ratio conditions with additive noise results in 79% recognition accuracy in the HMM-based classifier. We also compared the classification results of the data collected within the ear canal and outside the mouth via the same microphone. Average classification rates obtained for the data collected outside the mouth shows significant performance degradation (down to 63%), over that observed with the data collected from within the ear canal (down to 86%). The ear canal dampens high frequencies. As a result, the HMM model derived for the data with dampened higher frequencies does not accurately fit the data collected outside the mouth, resulting in degraded recognition performances.

Research was conducted on twenty-seven preoperative myringotomy patients to clarify the correlation between tympanometry type and the presence of middle ear effusion. Test results indicate that the relationship between tympanometry and middle ear effusion is dependent on the amount of fluid present. In impacted ears primarily Type B tympanograms were obtained whereas for less than impacted ears all tympanogram types were seen. Also suggested was that a combination of height of the tympanogram and the amount of negative pressure may be diagnostically more important than negative pressure alone as an indicator of effusion. It was recommended that other measures in addition to tympanometry be employed in the diagnosis of middle ear effusion and that further research is needed to achieve optimal use of impedance audiometry.

The purpose of this experiment is therefore (1) to design a test to measure the skill of a heterogeneous group of college music students and (2) to administer and evaluate an aural training program which could be used to develop efficiently aural intelligence. The students used in this experiment were intentionally chosen with varying abilities in order to permit comparisons. A careful record was kept of their ages, musical experiences, major instruments (voice, piano, violin, and other orchestral instruments), amount of training, skill and technique, and theory grades.

Fusarium Ear Blight (FEB) is a globally important floral disease of cereal crops such as wheat, maize and barley. The predominant causal agents of FEB disease of wheat in the UK are Fusarium culmorum and F. graminearum. Wheat infecting isolates of both of these fungal species infect the floral and silique tissues of the model plant Arabidopsis thaliana, providing a tractable model for analysis of factors determining plant susceptibility or resistance to Fusarium infection. The effect of F. culmorum infection on the metabolic composition (metabolome) of Arabidopsis pedicel tissue following silique inoculation was investigated in a collection of mutants with altered defence responses to F. culmorum and/or other plant pathogens, using a 1¬H-NMR/ESI-MS (+/-) triple fingerprinting approach. These mutants showed differing metabolomic fingerprints in the absence of F. culmorum infection, as well as differences in accumulation or depletion of metabolites in response to F. culmorum colonisation. A number of metabolites were also identified which were induced by F. culmorum infection irrespective of plant genotype. Quantitative differences in compound accumulation were also observed between genotypes in the Columbia and Landsberg erecta accessions following F. culmorum infection. One of the genotypes investigated was eds11, which has enhanced susceptibility to F. culmorum floral infection. Mapping of the mutation responsible for the eds11 phenotype was initiated using an isogenic mapping by sequencing approach. This resulted in a list of potential candidates for the EDS11 gene. Additional Arabidopsis mutants were investigated for altered defence responses to F. culmorum floral infection. Multiple mutant alleles of the Arabidopsis homoserine kinase gene DMR1 were found to have enhanced resistance to F. culmorum silique infection and rosette leaf colonisation, associated with accumulation of homoserine in siliques and delayed leaf senescence. Exogenous homoserine application enhanced resistance in wild type and dmr1 plants. Collectively, these findings form a novel contribution to current knowledge of the Fusarium-Arabidopsis interaction. This may have applications for improvement of FEB resistance in cereals.

Doctor of Philosophy / Biochemistry Interdepartmental Program / Antje Philine Wangemann / Mutations of SLC26A4 are the most common cause of the hearing loss associated with enlargement of the vestibular aqueduct. SLC26A4 encodes pendrin, an anion exchanger expressed in the cochlea, the vestibular labyrinth, and the endolymphatic sac of the inner ear. Slc26a4Δ/Δ mice, devoid of pendrin expression, develop an enlarged membranous labyrinth which leads to the failure to develop hearing, thereby recapitulating the human disease. Identifying the ionic composition of the endolymph and evaluating the importance of pendrin expression at various sites are initial steps towards developing strategies for preventing enlargement of the endolymph volume and subsequently restoring the inner ear functions. The major aims of the present study are 1) To determine the ionic composition of inner ear fluids during the developmental phase in which the enlargement of the endolymph volume occurs; 2) To test the hypothesis that pendrin expression in the endolymphatic sac is more important than its expression in the cochlea and the vestibular labyrinth. Here, we determined the Na+ and K⁺ concentrations in the cochlea and the endolymphatic sac with double-barreled ion-selective electrodes and generated a mouse model that restores pendrin expression in the endolymphatic sac while lacking expression in the cochlea and the vestibular labyrinth. High Na⁺ and low K⁺ concentrations were found in the cochlear endolymph during the embryonic stage. A rise of the K⁺ concentration along with a decline of the Na⁺ concentration occurred shortly before birth. The site-specific restoration of pendrin to the endolymphatic sac prevented enlargement and rescued hearing and balance. In conclusion, these data demonstrate that endolymph, in the phase of luminal enlargement during the embryonic development, is a Na⁺-rich fluid that is modified into a K⁺-rich fluid just before birth; restoration of pendrin in the endolymphatic sac is sufficient for developing normal inner ear function. Furthermore, these data suggest enlargement of endolymph volume caused by the loss of Slc26a4 is a consequence of disrupted Na⁺ absorption. Moreover, pharmacological strategies that correct fluid transport, as well as spatially and temporally limited restorations of pendrin, might restore normal inner ear functions in humans carrying mutations of SLC26A4.