A theoretical and experimental investigation into the penetration of parametric acoustic beams into sediment is conducted. The theory is based on the assumption that the interface completely truncates the array. With this assumption, the asymtotic farfield of the secondary radiation in sediment is developed and discussed. When the primary field is truncated in its nearfield, the secondary farfield is found to be due to two apertures, one coincident with the transducer and one with the truncation. At subcritical angles of incidence the field is similar to that produced by a conventional beam. At post-critical angles of beam incidence the presence of the truncation aperture results in a steeper and deeper penetration of the beam than in the conventional case. As the trucation moves into the farfield of the primaries, the effect of the truncation aperture is reduced until the parametric beam behaves qualitatively similar to a conventional beam. Experimental measurements of the secondary field throughout two vertical planes in the sediment are made, and are in good agreement with the theoretical predictions. The wide bandwidth of the parametric array is exploited to distinguish in time Snell's law and evanescent arrivals in the sediment. These latter are seen to be important close to the interface. It is concluded that the postcritical penetration of parametric sound beams into sediment is due to virtual secondary sources close to the interface and suitably phased.

Until this present work, the acoustics of waveguides has been divided into two broadly distinct fields---linear acoustics in ducts of complex geometry such as those with curvature or varying width, and nonlinear acoustics restricted to simple geometry ducts without curvature or flare. This PhD unites these distinct branches to give a complete mathematical description of weakly nonlinear wave propagation in a general shaped duct in both two and three dimensions. Such ducts have important applications---the clearest example is that of brass instruments, where it has been demonstrated that nonlinear wave steepening gives rise to the characteristic 'brassy' sounds of, for example, the trombone. As the ducts of these instruments have a very complicated geometry involving curvature, torsion and varying width, the goal of the PhD is to address what effect, if any, such changes in duct geometry have on the acoustic properties of such instruments. Other potential applications include the study of acoustics in curved aircraft engine intakes and even the nonlinear sound propagation through the trunk of an elephant. The first results chapter is focused on the exposition of the method used for the remainder of the paper, with the introduction of a new ``nonlinear admittance term'' as well as the associated algebra for it. An elegant notation for the nonlinear algebra is also developed, greatly simplifying the equations. The method is applied to one and two dimensional ducts and some analytical results are derived relating the work to previously published results. Numerical results are also presented and compared to other sources. The concept of nonlinear reflectance is also introduced---illustrating the effect of wave amplitude on the amount of energy reflected in a duct. The next results chapter builds on this work extending it to three dimensions. Numerical results are presented for three characteristic ducts---a curved duct, a horn and a helical duct, being one of the first works to study acoustics in helical pipes for both linear and nonlinear sound propagation. The final results chapter, utilising all of the previous work, addresses the problem of an open ended duct of finite length with nonlinear effects included. Results are compared with the linear results from the Wiener-Hopf method and new results are presented illustrating the effect of geometry and nonlinearity on the resonances of finite length waveguides culminating in the study of the resonances of a trombone.

<p> Generic predictions for the acoustic wavenumber at low frequencies in the condensational cloud layers of Venus are presented, based on and adapted from the terrestrial model of Baudoin <i>et al.</i> (J. Acoust. Soc. Am. <b>130.</b> 1142 (2011)). While the general thermodynamics of Earth clouds is well understood, that of Venusian clouds is still a matter of debate. Venus&rsquo; clouds are primarily formed of H₂O and H₂SO₄ vapors and aqueous sulfuric acid droplets, the fluxes of which are not fully constrained due to the few in situ observations. Inside the clouds, the Navier-Stokes-Fourier equations of continuum fluid mechanics are used for the gaseous (dry + vapor) and liquid phases of H₂O andH₂SO₄, combined with equations describing the evaporation/condensation processes; the gaseous phase is treated as an ideal gas and the liquid droplets are considered polydisperse. Thermophysical parameters are interpolated at the ambient conditions pertaining to an altitude of 50 km, a level where balloon platforms (e.g., European Space Agency&rsquo;s EVE) and manned airships (e.g., NASA&rsquo;s HAVOC) may be deployed in the future. At low frequencies, the dominant source of absorption is caused by the evaporation/condensation of the liquid phase. At higher frequencies, absorption is dominated by momentum transfers between the wave and the ambient gas and liquid droplets. The intrinsic dispersion is negligible. Sensitivity studies of the attenuation coefficient and the sound speed on the cloud physical parameters is performed, namely, the mean cloud particle size and the cloud density. The attenuation coefficient is sensitive to changes in both mean cloud particle size and cloud density, while the intrinsic dispersion changes negligibly. </p><p>

This thesis addresses the pressing concern of clinical drug-induced hearing loss (ototoxicity). Described herein is the mechanism by which ototoxicity emerges following drug administration both in a clinical setting and in an in vitro model assay system used for its investigation, through use of mouse cochlear cultures. The predominant nature of this research concerns the identification of novel otoprotectants - compounds that when co-administered alongside clinical drug treatments can prevent the unfortunate ototoxic side-effect from occurring. Here I present my research, focussing on the identification of a number of novel compounds that have the potential to be taken forward to in vivo screening and, ultimately, clinical trials. Moreover, for each identified compound I present my investigation of their mechanism of protection - which could arise either by preventing the entry of the ototoxicity-inducing drugs into the sensory hair cells of the inner ear, or prevent their induction of apoptosis once inside the cell. To investigate their protective mechanism I employed a variety of methods, including: electrophysiology, fluorescent imaging and mitochondrial respirometry. Conclusively, I have identified at least five novel otoprotectants with the potential for clinical use. I show that three of these compounds likely block the entry of the damaging drugs into sensory hair cells, whereas the remaining two are thought to work intracellularly. Moreover, the two most effective compounds that I have identified seemingly work intracellularly, suggesting this to be the most viable mechanism of otoprotection for further investigation. I also show the potential for compound modification based on their mechanism of protection as a way of improving a compound's otoprotective profile. Lastly, I devised an assay for the screening of clinical drug effects on mitochondria and employ this as a new avenue of screening for otoprotection.

Transforming sound vibrations into neural signals, the process of mechano-electrical transduction (MET), is achieved via the movement of rows of stereocilia located atop cochlear hair cells, activating non-selective MET channels. Recording MET currents using whole-cell patch clamp electrophysiology has allowed for various investigations centred on the MET channel. There is a statistically significant difference in MET current amplitudes between mid-apical and mid-basal outer hair cells. The larger MET current, flowing through basal hair cells explains a key contributory element to their increased susceptibility to the ototoxic effects of aminoglycoside antibiotics, as they are thus able to enter these cells more readily, in greater abundance. The cell penetrating peptides D-TAT and D-JNKi1 have been studied in cochlear hair cells. They are both high affinity, voltage dependent, permeant blockers of the MET channel in inner (IHCs) and outer hair cells (OHCs). Whilst ototoxic at higher concentrations, they may have therapeutic potential at lower concentrations, providing ototoprotection against aminoglycoside induced ototoxicity by competitively blocking the MET channel. There is an apical to basal gradient in the OHC MET channel block caused by D-TAT and D-JNKi1, the affinity of the block increasing from apex to base. Compellingly, the first evidence of a gradient in the MET channel properties of IHCs is presented here, a gradient in D-JNKi1 block. Properties of an anomalous mechano-sensitive current, elicited by inverse stimuli relative to the MET current, have been elucidated via the use of the compounds dihydrostreptomycin (DHS) and FM1-43. When compared with the MET current, DHS block of the anomalous current is two orders of magnitude less strong and FM1-43 block has altered voltage dependence. TRPC3/6 knock-out mice, whilst previously thought to have a basal OHC specific MET deficit, have been shown to exhibit normal MET currents. In addition, so too have TRPC1/3/6 and TRPC1/3/5/6 knock-out mice.

Structural Health Management (SHM) combines the use of onboard sensors with artificial intelligence algorithms to automatically identify and monitor structural health issues. A fully integrated approach to SHM systems demands an understanding of the sensor output relative to the structure, along with sophisticated prognostic systems that automatically draw conclusions about structural integrity issues. Ultrasonic guided wave methods allow us to examine the interaction of multimode signals within key structural components. Since they propagate relatively long distances within plate- and shell-like structures, guided waves allow inspection of greater areas with fewer sensors, making this technique attractive for a variety of applications.;This dissertation describes the experimental development of automatic guided wave interpretation for three real world applications. Using the guided wave theories for idealized plates we have systematically developed techniques for identifying the mass loading of underwater limpet mines on US Navy ship hulls, characterizing type and bonding of protective coatings on large diameter pipelines, and detecting the thinning effects of corrosion on aluminum aircraft structural stringers. In each of these circumstances the signals received are too complex for interpretation without knowledge of the guided wave physics. We employ a signal processing technique called the Dynamic Wavelet Fingerprint Technique (DFWT) in order to render the guided wave mode information in two-dimensional binary images. The use of wavelets allows us to keep track of both time and scale features from the original signals. With simple image processing we have developed automatic extraction algorithms for features that correspond to the arrival times of the guided wave modes of interest for each of the applications. Due to the dispersive nature of the guided wave modes, the mode arrival times give details of the structure in the propagation path.;For further understanding of how the guided wave modes propagate through the real structures, we have developed parallel processing, 3D elastic wave simulations using the finite integration technique (EFIT). This full field, numeric simulation technique easily examines models too complex for analytical solutions. We have developed the algorithm to handle built up 3D structures as well as layers with different material properties and surface detail. The simulations produce informative visualizations of the guided wave modes in the structures as well as the output from sensors placed in the simulation space to mimic the placement from experiment. Using the previously developed mode extraction algorithms we were then able to compare our 3D EFIT data to their experimental counterparts with consistency.

acase@tulane.edu

Musical expression is largely dependent upon accentuation, yet there have been few attempts to study the perception of dynamic accent in music or to relate the results of psychoacoustical research in intensity to realistic musical situations. The purpose of the experiment was to estimate the relationships among (a) the intensity increment in dB(A) required to meet an 80% correct criterion in the perception of one accented tone embedded within a seven-tone isochronous series of identical 87 dB(A) snare drum timbre stimuli of 333 ms onsets (accent level, or AL), (b) the different limen (DL) for intensity increase to meet a 75% correct criterion in a 2AFC task for pairs for the stimuli, and (c) the age of the subjects, all of whom have normal audiograms. / The 51 subjects (N = 51) were female nonmusicians ranging in age from 9 to 33 years (M = 17.98, SD = 5.21). The response tasks involved saying whether the second tone of each pair was louder or softer and circling the accented note in notated quarter notes. The stimuli production, the headphone calibration process, and their rationales were detailed. The global regression model was significant (F(2, 48) = 5.505, p =.007, $R\sp2$ =.187), and the relationship between AL and DL was not significant (F(1, 48) = 5.505, p =.197, $R\sp2$ change =.029), the relationship between AL and age was significant (F(1, 48) = 5.732, p =.021, $R\sp2$ change =.098) at an alpha level of.05 and power calculated at.66 for a medium ES. / It was concluded that accented sounds are easier to perceive in tone pairs than they are in a musical setting and that subject maturation improves performance of intensity judgement tasks. Suggestions for further research include shortening the length of the experimental session for younger subjects and increasing the number of intensity increments as well as using smaller increments to accommodate individual differences in perception. / Source: Dissertation Abstracts International, Volume: 53-03, Section: A, page: 0662. / Major Professor: Jack A. Taylor. / Thesis (Ph.D.)--The Florida State University, 1992.

To acquire heat transfer measurements of a high temperature Mach two flow a water-cooled calorimeter was placed in the flow and the water temperature rise was used to calculate the heat transfer rate and the recovery temperature of the gas. In addition, a graphite rod with a stainless steel tube at its core was used to measure the total pressure of the flow. This pressure probe was swept through the flow for two test runs to acquire a stagnation pressure profile of the gas flow. All results were compared to NASA CEA computer simulation code results. The heat transfer and recovery temperature results agreed well with the computer simulation code, while the total pressure results from the probe data agree excellently with the computer simulation code. A sensitivity analysis on the results was also preformed on the results.

Noise from heavy trucks is an important environmental issue. Several sources contribute to the total noise level of a vehicle, such as the engine, gearbox, tires, etc. The tonal noise from the gearbox can be very disturbing for the driver, even if the noise level from the gearbox is lower than the total noise level. The human ear has a remarkable way of detecting pure tones of which the noise from loaded gears consists of. To be allowed to sell a heavy truck within the European Union, the so called pass-by noise test must be completed successfully. The maximum noise level permitted is 80dB(A) and undercertain conditions, the gearbox can be an important contributor to the total noise level. Gear noise is therefore an important issue for the automotive industry. In this thesis gear noise and dynamic transmission error is investigated. Traditionally, transmission error (TE) is considered to be the main excitation mechanism of gear noise. The definition of TE is ”the difference between the actual position of the output gearand the position it would occupy if the gear drive were perfect”. Measurements of dynamic transmission error (DTE) and noise have been performed on a gearbox. The measurement object was a commercial truck gearbox powered by an electrical motor. The torque used was in the normal operating range of the gearbox and the correlation between gear noise and DTE, when the torque is changed, is investigated. The result differs for different gear pairs and for the first gear stage, located close to the housing, the correlation is high for most speeds. The measured DTE and noise show a poor correlation with calculated transmission error. A minimisation of TE therefore does not necessarily mean a minimisation of gear noise. A transfer function can be employed to calculate the relationship between DTE and noise. The general trend of the gear noise is an increase of 6dB per doubling of the rotational speed together with fluctuations around the mean due to resonances of the system. The magnitude of the transfer function can be estimated using the amplitudesof the gear mesh orders and harmonics. Two gear pairs with similar macro geometry but different profile modifications are investigated. Although the gear pairs have similar transmission error, the noise level display a significantly different trend, further strengt hening the position that transmission error is not the single most important gear noise excitation mechanism. Further analysis concludes that shuttling forces and friction forces can be more important than what is often suggested. A dynamic model including transmission error and shuttling forces is used to investigate the two gear pairs. The bearing forces show that for some frequency regions shuttling forces can be of the same order of magnitude as the forces caused by transmission error. This work highlights the importance of considering other excitations of gear noise besides transmission error when designing quiet gears. The influence of transmission error can not be determined by investigating the gears only. A deeper knowledge of the gear system is needed in order to minimise gear noise for a specific gear design. / QC 20100719