Integration of duration and frequency in discrimination between pure tones

This dissertation investigates discrimination between pure tones. Three questions were investigated: can listeners integrate frequency and duration information in the discrimination of pure tones; how does the discriminability of duration-frequency compounds relate to the discriminability of the changes in the individual dimensions; and how is the integration of these two dimensions affected by the parameters of the stimuli in which the changes in duration and frequency are introduced.

Frequency responses of hearing aids and their effects on the speech perception of eight hard-of-hearing subjects

This dissertation examines the relationship between frequency response and word-discrimination performance of hearing-impaired persons. Three questions are addressed: does the restoration of the normal field-to-eardrum transfer function improve word discrimination; is the restoration of the normal shape of the audibility curve (uniform hearing level at all frequencies) beneficial to hearing-impaired listeners; and can speech discrimination be improved by an extension of the present narrow-band response in hearing aids.

Threshold adaptation, temporal integration and frequency discrimination-learning in hearing impaired children

This paper is a review of a study to evaluate the usefulness of a laboratory approach to auditory training with hearing impaired children.

Are there hazardous auditory effects of high-frequency turbines and ultrasonic dental scalers on dental professionals?

The purpose of this pilot study was to survey dentists in the St. Louis area to assess their subjective opinion of commonly used dental handpieces as well as history of noise exposure and use of hearing protection. Selected handpieces were then chosen to measure their output levels and determine if emissions are hazardous to the auditory system.

Differential sensitivity to tonal frequency and to the rate of modulation of broad-band noise by hearing-impaired listeners

This dissertation examined whether a hearing impairment of the auditory end-organ has the same or a differential effect on the place and periodicity processes. Differential sensitivities for four normally hearing listeners and for both ears of five patients with unilateral Meniere’s disease were measured for tonal frequency and rate of sinusoidally amplitude-modulated noise at common frequencies and rates of the stimulus.

Difference between default telecoil and programmed microphone frequency response in behind-the-ear hearing aids

The notion that the default telecoil (t-coil) frequency response should match the programmed microphone frequency response to provide optimal telephone understanding for hearing aid patients has received little attention. This study addresses differences in the average frequency response of the two transducers in behind-the-ear (BTE) hearing aids.

Detection of Parkinson’s disease tremor-onset with a frequency analysing artificial neural network

Deep Brain Stimulator devices are becoming widely used for therapeutic benefits in movement disorders such as Parkinson's disease. Prolonging the battery life span of such devices could dramatically reduce the risks and accumulative costs associated with surgical replacement. This paper demonstrates how an artificial neural network can be trained using pre-processing frequency analysis of deep brain electrode recordings to detect the onset of tremor in Parkinsonian patients. Implementing this solution into an 'intelligent' neurostimulator device will remove the need for continuous stimulation currently used, and open up the possibility of demand-driven stimulation. Such a methodology could potentially decrease the power consumption of a deep brain pulse generator.

The frequency and dynamics of stratospheric sudden warmings in the 21st century

Changes to stratospheric sudden warmings (SSWs) over the coming century, as predicted by the Geophysical Fluid Dynamics Laboratory (GFDL) chemistry climate model [Atmospheric Model With Transport and Chemistry (AMTRAC)], are investigated in detail. Two sets of integrations, each a three-member ensemble, are analyzed. The first set is driven with observed climate forcings between 1960 and 2004; the second is driven with climate forcings from a coupled model run, including trace gas concentrations representing a midrange estimate of future anthropogenic emissions between 1990 and 2099. A small positive trend in the frequency of SSWs is found. This trend, amounting to 1 event/decade over a century, is statistically significant at the 90% confidence level and is consistent over the two sets of model integrations. Comparison of the model SSW climatology between the late 20th and 21st centuries shows that the increase is largest toward the end of the winter season. In contrast, the dynamical properties are not significantly altered in the coming century, despite the increase in SSW frequency. Owing to the intrinsic complexity of our model, the direct cause of the predicted trend in SSW frequency remains an open question.

Boundary integral methods in high frequency scattering

In this article we review recent progress on the design, analysis and implementation of numerical-asymptotic boundary integral methods for the computation of frequency-domain acoustic scattering in a homogeneous unbounded medium by a bounded obstacle. The main aim of the methods is to allow computation of scattering at arbitrarily high frequency with finite computational resources.

Condition number estimates for combined potential boundary integral operators in acoustic scattering

We study the classical combined field integral equation formulations for time-harmonic acoustic scattering by a sound soft bounded obstacle, namely the indirect formulation due to Brakhage-Werner/Leis/Panic, and the direct formulation associated with the names of Burton and Miller. We obtain lower and upper bounds on the condition numbers for these formulations, emphasising dependence on the frequency, the geometry of the scatterer, and the coupling parameter. Of independent interest we also obtain upper and lower bounds on the norms of two oscillatory integral operators, namely the classical acoustic single- and double-layer potential operators.