bluuebunny/crossref_metadata_2025 huggingface dataset:
Broadband transducer requirements and development for a synthetic aperture sonar
Authors: Fernandez Jose E. , Christoff James T. , Commander Kerry W. , Cook Daniel A.
Published: February 2014

Broadband acoustic signal transmission and reception are key to enhancing the performance of underwater acoustical sensor systems to support functions like underwater acoustic communications and high resolution underwater imaging. In particular, synthetic aperture sonar (SAS) is an attractive technology for high-resolution imaging because of its ability to produce better cross range resolution than that of a real aperture array sonar of the same length. In addition, SAS systems can produce a cross range resolution that is independent of frequency and range. When the advantages of a SAS system are coupled with those gained from going to a broadband signal space, the performance enhancements can be significant. Specifically improvements in clutter rejection, object classification, and area coverage rate will be achieved. A description of the transducer requirements and expected payoffs for a SAS system designed to operate and image proud and buried objects in shallow waters will be presented. [Work supported by ONR.]
Wideband 1–3 piezoelectric composite parametric mode projectors for UUV/AUV applications
Authors: Benjamin Kim C.
Published: February 2014

Unlike conventional parametric mode projectors, the 1–3 piezoelectric composite-based parametric mode projector affords a broad frequency range of operation. Due to its intrinsically low mechanical quality factor, Qm, the 1–3 piezoelectric composite material allows a wide range of primary frequencies to be used to excite the parametric mode effect. Furthermore, unlike conventional parametric mode projectors, the 1–3 piezoelectric composite substrates do not require inherently narrow band tuning circuits to enhance their half-wave resonance frequency. This presentation will report on the design and measured results for two 1–3 piezocomposite-based parametric mode projectors. The first case consisted of a 23-mm-diam by 6-mm-thick active layer driven with primary frequencies centered about 200 kHz. Beamwidths of 3.5 to 4.0 degrees were realized at differences frequencies ranging from 5–50 kHz. In the second case, a 15-mm by 15-mm by 25-mm-thick active layer was driven with primary frequencies centered about 60 kHz. In this case beam widths of 8.5 to 9.0 degrees were realized at difference frequencies ranging from 1 to 10 kHz.
Using your ears to learn about the acoustics of metal tubes
Authors: Kaczmarek Konrad
Published: February 2014

The goal of this experimental work was to ascertain to what degree the physical properties and oscillatory behavior of a material can be understood using only one’s ability to hear and a few simple tools such as a ruler, a scale, and a piano. More specifically, by striking a metal pipe in various controlled ways, listening to the resonance frequencies of various modes, and then matching the pitches heard to those found on a piano, such physical properties as the Young’s modulus and the velocity of sound in a medium (air and solid) can be derived. Similarly, more complex scenarios such as end corrections in air resonances and transverse modes of vibration can be described fairly accurately using only these prescribed tools. The accuracy of this method was checked using traditional instrumentation (microphone and spectrum analyzer). [Advisor, Professor Robert E. Apfel.]
Nonlinear scattering of crossed ultrasonic beams in the presence of turbulence: Experiments performed with pulses
Authors: Manry Rebecca A. , Korman Murray S.
Published: February 2014

The nonlinear scattering of two finite-amplitude mutually perpendicular crossed beams—interacting in the presence of turbulence—generates a sum frequency component that radiates outside the interaction region. Experiments are reported where two primary pulsed (f1=2.35 MHz and f2=1.65 MHz) focused beams are generated by 2.54-cm-diam concave spherical transducer units (T1 and T2) of focal length 14 cm. The 4-MHz receiving unit (R) is a 2.54-cm-diam circular plane array. The turbulence is generated by a D=0.635-cm-diam submerged circular water jet (nozzle exit velocity 7 m/s) whose orifice is located at 56D from the interaction region. All transducer beam axes and jet axis form a common plane. A scattering region is formed at the intersection of the focal points of the primary beams. While T1 and T2 rotate on radius arms—always keeping the beams perpendicular—R is fixed. Symmetry suggests a scattering angle θ*, where θ*=0 defines forward scattering. Ensemble averaged rms pressure spectra (near the sum frequency) are measured (1) as a function of angle and fixed pulse duration τ=100 μs, and (2) at θ*=0 and variable τ in an effort to compare spectral broadening with our theory.
Objective measurements in Strauss Recital Hall at the University of Nebraska
Authors: Rock Jessica L. , Wang Lily M.
Published: February 2014

This poster presents measured acoustical data in a performing arts hall, obtained from three different measurement techniques and with various sound source and receiver positions. The room under study is Strauss Recital Hall, located on the campus of the University of Nebraska at Omaha. Sound decay measurements are taken between selected source and receiver positions in three ways: triggered by an impulse source such as a balloon pop; triggered by the end of steady-state white noise; and using a maximum length sequence (MLS) source. The measured responses are used to calculate the reverberation time, clarity index, strength, interaural cross-correlation coefficient, and other room acoustic measures. Analysis of the data focuses on how these objective measures change across the Hall and how they differ between measurement techniques. Additionally, the data obtained are compared to values from other renowned halls.
Neighborhood soundscapes: Measurement and identification issues
Authors: Klåboe Ronny
Published: February 2014

The term neighborhood soundscape has been coined to describe the amount of road traffic noise in the immediate neighborhood of a dwelling. A simple indicator of how much the road traffic noise level in the neighborhood exceeds the noise level at the dwelling has been developed using a geographical information system. By applying the indicator with data from several socio-acoustic surveys it has been shown that people living in a relatively noisy neighborhood are significantly and substantially more annoyed than follows from the residential road traffic noise level alone. However, this does not prove that the heightened annoyance is caused by the noise exposure in the neighborhood. Neighborhood road traffic also gives rise to traffic insecurity and local air pollution, and indicators of these environmental exposures are additional possible effect modifiers. To separate the different positively correlated modifying effects, it is therefore not enough to measure the neighborhood soundscape, but also measure relevant aspects of the environscape. To statistically separate the different modifying effects requires that the respective measures are sufficiently precise. To go beyond the purely statistical associations it is also necessary to link each measure to the respective psychscape impacts and model the relevant parts of the psychscape.
How structural parameters values can act on subjects’ preference judgments for sounds transmitted by a simple component of an exterior wall
Authors: Marquis-Favre Cathy , Faure Julien
Published: February 2014

For a long time, the vibroacoustic behavior of structures was studied from a physical point of view with the goal of reducing sound levels and understanding physical phenomena. It has led researchers to elaborate upon physical models for sound radiation and transmission prediction, and also to establish vibroacoustic indicators such as radiation efficiency or sound transmission loss for acoustic performance criteria. Within the last decade, qualitative aspects of sounds have been integrated into the physical analysis to take into account sound perception and the expectation of subjects. This has yielded noticeable improvements in the sound quality of sources in various industries, mainly in the automotive industry. Our work aims at improving the acoustic performance of building structures which act as input filters to annoying sounds of the inner environment. The approach is based on coupling of the physical and perceptual analyses. We will present how structural parameter values and their accuracy can act in a non-negligible manner on the similarity and preference judgment of subjects for broadband noises transmitted by a simple panel of an exterior wall. This is observed even in the case of structural parameter variations that induce no significant modification of vibroacoustic indicators such as sound transmission loss.
Correlation between acoustical sensory profiles and physical measures of product sound
Authors: Bowen David L. , Lyon Richard H.
Published: February 2014

‘‘Sensory profiles’’ (SPs) are used extensively for judgments of taste, odor, and texture—situations where a useful physical metric is not available. An acoustical SP can be obtained using a panel of critical listeners, and can provide a bridge between descriptions of a sound and the sound quality (SQ)—judgments that consumers make about a product based on the sound it makes. But as descriptors, SPs also offer the opportunity to connect to physical measures of the sound. If the description is ‘‘tinny’’ or ‘‘shrill,’’ there is expectation of a high-frequency bias to the sound. If the description is ‘‘throbbing’’ or ‘‘knocking,’’ a modulation of the sound is expected. Since spectral balance and modulation are measurable, some kind of transformation between the SP and physical measurements is reasonable. This presentation focuses on the issue of the robustness of such a relationship, since it is desired that the physical measurements be able to predict or relate to a significant variation in the SP. Examples are given from studies of vacuum cleaner and washing machine sounds of the sensitivity of SQ to changes in the SP, and therefore of the variations in physical measures that are significant in terms of variations in SQ. [Work supported by NSF.]
Passive stabilization of capillary bridges in air with acoustic radiation pressure and the equilibrium shape of bridges
Authors: Marr-Lyon Mark J. , Thiessen David B. , Marston Philip L.
Published: February 2014

Long liquid cylinders ordinarily become unstable because of a capillary instability originally studied by Rayleigh and Plateau. In the present research liquid bridges in air were acoustically stabilized to 43% beyond the natural limiting length identified by Rayleigh and Plateau [Marr-Lyon, Thiessen, and Marston, Phys. Rev. Lett. (to be published)]. The stabiliza-tion was achieved by placing the bridge at the velocity antinode of a standing wave and selecting the wavelength such that the surface-averaged radiation pressure of the sound field increases with increasing bridge radius. The tests were performed on NASA’s KC-135 aircraft in weightless conditions on bridges having volumes equal to that of a circular cylinder of the same length as the bridge. In the standing wave, the bridge becomes elliptical because of the spatial distribution of the radiation pressure. Calculations of the scattering of sound by elliptical cylinders using Mathieu functions show that elliptical deformation only weakly affects the average increase in the radiation pressure with the local bulging of a liquid bridge normally associated with the Rayleigh-Plateau instability. [Work supported by NASA.]
Acoustic cavitation thresholds and stable oscillations of vapor-gas bubbles
Authors: Gumerov Nail A.
Published: February 2014

The effect of rectified diffusion on the behavior of gas bubbles and the effect of rectified heat transfer to vapor bubbles are well established. These effects may be equally important for dynamics of vapor-gas bubbles and control the acoustic cavitation thresholds. To describe these effects a model of a spherical vapor-gas bubble is used. This model accounts for heat and mass transfer in the two-component system, including Soret–Dufour effects, kinetics of evaporation, surface tension, liquid viscosity, and compressibility. Equations for acoustic cavitation thresholds and stable bubble oscillations are obtained using asymptotic averaging techniques valid to second order in the amplitude of the acoustic field. Good agreement between the previous results for gas and vapor cavitation thresholds and the present computations is observed in the limiting cases of single-component bubbles. The effects of temperature, kinetics of evaporation, supersaturation, and others on the acoustic cavitation thresholds and stable bubble oscillations are studied and discussed. The existence of stable oscillations and cavitation thresholds of the bubble due to the second resonance of a vapor-gas bubble is predicted. These states occur due to the two-component nature of the bubble and appear at low inert gas concentrations near the liquid boiling point.
Towards an intense bubble
Authors: Khong Anthony , Doschek Elizabeth , Mori Jonathan , Apfel Robert , Ketterling Jeffrey
Published: February 2014

A main goal in SBSL remains the ability to form a bright and hot bubble. One recent postulate suggests that lowering the resonance frequency should favor a stronger luminescing bubble. It is also theorized that the chemical composition of the bubble can be streamlined to induce a more violent collapse. The water vapor content inside the bubble is considered. The premise of this conjecture is that water vapor molecules, present beyond equilibrium concentrations, act to siphon energy from the bubble, and in the process undergo thermal decomposition. Hence, reducing the water vapor content should eliminate such energy loss. The current study focuses on this issue. Keeping similar driving conditions, there is interest in using aqueous salts to depress the vapor pressure of the water in tandem with a reduction in the water temperature. A series of alkali metal halides will be examined. In a preliminary investigation, a 9% lithium chloride solution saturated with 1% argon gave stable SL at room conditions. With air, no SL was detected. A further extension of this work would be to determine the bubble temperature which has largely been inferred. [Work supported by DARPA through a subcontract from the University of Washington.]
Pulse-echo ultrasonics from the correlations of thermal phonons
Authors: L. Weaver Richard , I. Lobkis Oleg
Published: February 2014

A high-sensitivity acoustic emission transducer in contact with a non-insonified solid body generates a noise signal, a significant fraction of which is due to thermal fluctuations in the body. This is established by comparisons of the spectral power density of its noise and the spectral power density consequent to the application of a calibrated source. This high sensitivity is some 30 dB greater than that of other ultrasonic transducers. As established elsewhere [Weaver and Lobkis, this meeting] the correlations of a diffuse field are related to the local density-of-ultrasonic-modes, and thus to local responses in pulse/echo. It is therefore hypothesized that the autocorrelation function of the noise in a high-sensitivity transducer should equal the pulse-echo signal generated by that transducer. The hypothesis is investigated by constructing that autocorrelation function (the autocorrelation appears to converge after only a few tens of milliseconds of data collection) and comparing it with the pulse/echo signal. The two waveforms are found to be substantially identical. The reasons for the differences are discussed, and possibilities for application are considered. [Work supported by NSF.]
Diffraction correction and attenuation of high-frequency acoustic pulses in a relaxing medium
Authors: Dain Yefim , Lueptow Richard M.
Published: February 2014

The influence of intrinsic absorption in a relaxing medium and the diffraction correction for the magnitude of the acoustic pressure averaged over the surface of a receiver was investigated. An exact formula for the damped acoustic pressure averaged over the surface of the receiver was obtained for high-frequency modulated pulses in a mono-relaxing medium. The formulation is based on the solution of a modified wave equation in a relaxing medium. Based on asymptotic analysis, separate effects result for the attenuation of the pulse envelope and for the modulation of the carrier frequency for high-frequency pulses with an arbitrary envelope shape. The resulting distortion of the energy spectrum for arbitrary pulses depends on the medium’s relaxation frequency and the acoustic carrier frequency. These results are useful in predicting the response of transducers in a relaxing medium. [Work supported by Ford Motor Company.]
A nonlinear analysis of piezoelectric coated laminae
Authors: Dokmeci M. Cengiz , Altay G. Askar
Published: February 2014

In relation to vibrations of piezoelectric materials subject to strong electric fields and large strains, a system of 2-D nonlinear laminae equations is derived by the use of Mindlins kinematic hypothesis for each layer. The laminae is coated completely with perfectly conducting electrodes on both its faces, and it may comprise any number of bonded layers, each with a distinct but uniform thickness and electromechanical properties. By use of a recent variational principle [Altay and Dokmeci, Thin Walled Struct. 39, 95–109 (2001)], the system of equations is consistently formulated in both invariant, differential and variational forms. The effects of elastic stiffnesses of, and the interactions between, layers of laminae are all taken into account. The system of equations governs the extensional, flexural, and thickness shear as well as coupled vibrations of piezoelectric laminae. Special types of vibrations, geometry, and material properties are recorded. Besides, the uniqueness is investigated in solutions of the initial-mixed boundary value problems defined by the linearized system of laminae equations. [Work supported in part by TUBA.]
Microfluidic amplification of ultrasound with application to MEMS hydrophones
Authors: Cleveland Robin O. , Pascual Daniel N. , Johnson Harley T. , Bifano Thomas G. , Pierce Allan D.
Published: February 2014

Micro-electro-mechanical systems (MEMS) were used to fabricate a device with passive fluidic components that amplified the motion associated with ultrasonic waves in water. Two types of fluid components were etched in silicon, an acoustic horn, and an acoustic resonator. The fluid motion was detected by a small silicon diaphragm which moved with the sound wave. The diaphragm motion was measured with a laser Doppler vibrometer. Experiments were carried out for acoustic excitations in the frequency region of 0.5 to 5 MHz. Over this frequency range uniform thickness diaphragms were found to support multiple resonance modes and were found to be poor sensing surfaces. Composite diaphragms, with a stiff pedestal supported by compliant edge fixtures, provided a superior sensing surface. The motion of the diaphragm placed at the throat of an acoustic horn demonstrated broadband amplification with a gain of 6. An organ-pipe type resonator provided a narrow-band gain of 3. The horn and resonator structures could be incorporated into most types of MEMS hydrophone devices which use diaphragms to sense sound waves. [Work supported by DARPA.]
Relation between the slope of the rate-level curve, the maximum driven firing-rate, and the neuronal dynamic range in auditory primary afferents of the cat
Authors: Nizami Lance , McGee JoAnn , Walsh Edward J.
Published: February 2014

The power of the auditory primary afferent to indicate intensity change depends partly upon the rate-of-change-of-firing with sound-pressure-level, i.e., the slope of the rate-level curve. The latter was estimated for each of 778 rate-level-functions in the cat (McGee, MS thesis, Creighton, 1983) by fitting lines to the points on the curve that fall between (1) Rs+[c/100](Rmax−Rs) and (2) Rs+[(100−c)/100](Rmax−Rs), for c=30. Rs is spontaneous firing-rate and Rmax is maximum firing-rate. c specifies a pair of points on the curve, symmetric around the centroid. Each slope was divided by the respective maximum driven firing-rate, Rmax−Rs, to obtain the adjusted slope (in 1/dB). Each adjusted slope was then plotted versus the neuron’s dynamic range (in dB), whose endpoints, the threshold and the saturation level, are given by c=1. The resulting plot is smooth and hyperbolic. Threshold and saturation level have also been defined by expressions (1) and (2) in a logistic rate-level equation (Nizami, 24th ARO, 2001) that yields (3) adjusted slope =[ln[(100−c)/c]]/2(dynamic range)]. For c=1 and c=2, these curves neatly sandwich the empirical data. An afferent’s power of discrimination is intimately related to both the maximum driven firing-rate and the neuronal dynamic range.
Effect of duration and level of the recalibration tone on the amount of loudness recalibration
Authors: Nieder Bärbel , Buus So/ren , Florentine Mary , Scharf Bertram
Published: February 2014

The amount of loudness recalibration (i.e., the drop in loudness of a moderate-level tone caused by a preceding intense recalibration tone of the same frequency) was measured as a function of the recalibration tone’s duration and level using a 2AFC procedure. The 500-Hz test tone—presented at 60 and 70 dB SPL—and the 2500-Hz variable-level comparison tone both lasted 200 ms. Results for 10 normal listeners show that 5-ms recalibration tones yielded only 3 (test tone at 60 dB SPL) to 4 dB (at 70 dB SPL) of recalibration, whether their level was 80, 95, or 110 dB SPL. In contrast, 200- and 500-ms recalibration tones at 80 and 95 dB SPL (200 ms only) yielded 6 (at 60 dB SPL) to 10 dB (at 70 dB SPL) of recalibration, again with no apparent effect of level. Note that 5-ms recalibration tones at 95 dB SPL yielded much less recalibration than 200-ms recalibration tones at 80 dB SPL, despite their nearly equal loudness. These data indicate that recalibration is not governed by the loudness of the recalibration tone and that recalibration-tone duration is a crucial parameter for recalibration of loudness. [Supported by NIH/NIDCD R01DC02241.]
Further progress with loudness adaptation inside and outside the speech range
Authors: Boudouris Sophia , Cross Kathleen , Boyce Suzanne , Kretschmer Laura , Sandman David E. , Weiler Ernest M.
Published: February 2014

Measurement of loudness adaptation at 4000 Hz and below depends on the technique used [Weiler et al., J. Acoust. Soc. Am. 101, 3171(A) (1997); T. Maguire et al., J. Acoust. Soc. Am. 106, 2207 (1999)]. Further comparison of simple adaptation (SA) to the ipsilateral comparison paradigm (ICP) with repeated measures designs again shows adaptation for both techniques at 8000 Hz but stronger effects for the ICP now. At 6000 Hz only, violations of normal curve parameters were again observed but no SA. Observations at 250 Hz for the ICP and SA will be discussed. The difference in adaptation between the two techniques is extreme in the primary speech frequencies but intermediate at 8000 Hz for our repeated measures designs. Further investigation is planned.
History of physiological acoustics: A modeling perspective
Authors: Sachs Murray B.
Published: February 2014

Since the days of Helmholtz and Ohm in the nineteenth century, physiological acoustics has focused on models of mechanisms underlying human auditory perception. We review the history of three modeling streams: (1) models of cochlear mechanisms, (2) models that predict human psychoacoustic performance on the basis of neural representations of sound, and (3) models for processing of acoustic information by the central nervous system. We trace the evolution from early macromechanical models that were adequate to explain the broad tuning of the basilar membrane as reported by von Bekesy to recent micromechanical models needed to account for sharp basilar-membrane tuning as revealed by more sensitive experimental techniques. We review models of the molecular mechanisms underlying hair cell electromotility and its relation to sharp tuning. Because of the ‘‘dynamic range problem’’ early models of frequency and intensity discrimination based on auditory-nerve discharge rates gave way to models based on temporal properties of auditory-nerve firing patterns. Discovery of a population of fibers with broad dynamic ranges revived interest in rate-based models. Studies of information processing in the central auditory system have been shaped by models for the representation of the frequency, intensity, and spatial characteristics of acoustic stimuli.
Transfer matrix method for mufflers modeling and experimental verification
Authors: Thieme Fabio A. , Gerges Samir N. Y. , Coelho Jos L. B.
Published: February 2014

Mufflers are very important elements in industry for the attenuation of exhaust noise in vehicles and machinery. Recent advances in modeling procedures, for accurate performance prediction, lead to the development of the transfer matrices method for more practical muffler components appearing in commercial designs. Muffler designers are looking for simple, quick modeling tools, especially in the preliminary evaluation stages of a design. Finite element (FEM) and boundary element (BEM) methods, in spite of giving results in a wide range of frequencies, are still expensive, need very skilled operators, and commercial software is still not user friendly. Plane wave modeling, using the transfer matrix form, offers a cheap and quick method for muffler designers to arrive at an initial prototype solution. In this paper, transmission loss calculations are presented for several practical muffler configurations in explicit formulas and comparison with experimental results are presented.
Theoretical development and experimental verification of polyvinylidene flouride sensors for measurement of the local volume displacement of beams
Authors: Rozema Randall , Zellers Brian , Naghshineh Koorosh , Zahui Marcellin
Published: February 2014

One method of reducing the sound radiated from vibrating structures at lower frequencies is to reduce the volume displacement of the vibrating surface (via active control). At these low frequencies, the volume displacement is directly proportional to the sound power emitted from a vibrating surface. To extend the effective frequency range of the active control system, several systems that reduce the volume displacement over localized areas of structural surface were employed. Thus, means of measurement of structural surface volume displacement become important. A traditional approach is to employ multiple point sensors (accelerometers). Recently, a single sensor made of polyvinylidene fluoride (PVDF) was utilized and found to represent an attractive solution. These sensors, which were designed to measure the structural volume displacement over a segment of structural surface, spanned the entire length of the structure. Such arrangement was found to be inefficient. In the work presented here an integrated sensor comprised of a shaped PVDF strip in addition to two point sensors located at the ends of this strip. The entire sensor does not extend beyond the segment of interest, thus, labeled a local sensor. Theoretical development of these sensors, fabrication techniques, and verification of these sensors will be presented.
Investigation of local volume displacement sensors for rectangular vibrating plates
Authors: Christensen Mark , Hoofnagle Ron , Naghshineh Koorosh , Zahui Marcellin
Published: February 2014

Further development and validation of a technique for measurement of local volume displacement is presented. This development supports the implementation of noise control techniques that are based on minimization of local volume displacements, velocities, or accelerations of a vibrating structure. In this work, we present a brief description of the methodology for designing such sensors fabricated using polyvinylidene fluoride (PVDF) film followed by the experimental verification of these sensors for a vibrating clamped–clamped plate comprising one side of an otherwise rigid box. These experimental results were then compared against predicted values.
A passive means for cancellation of structurally radiated tones
Authors: Zapfe Jeffrey A. , Ungar Eric E.
Published: February 2014

The mass of a spring–mass system whose spring is driven at a given frequency vibrates in opposite phase to the excitation, provided that the system’s natural frequency is lower than the excitation frequency. If this natural frequency also is near the excitation frequency, then the amplitude of the mass can be considerably greater than that of the driving motion. These ideas were applied to construct radiation-canceling devices that act like resiliently supported masses with significant sound radiating areas, so that radiation from these could cancel the sound radiated from considerably larger vibrating surfaces to which these devices may be attached. The sound radiation from such devices and the attendant reduction in the sound radiated from sample structures were analyzed, some experimental prototype devices were built, and their effects were measured. Devices of this type are thought to be useful for reducing the sound radiation from equipment items, such as transformers, which vibrate and radiate noise at a fixed frequency. [Patent pending.]
Sound insulation analysis of solid walls using the finite element method
Authors: Ackermann Lutz , Antes Heinz
Published: February 2014

In times of increasing noise pollution, the numerical simulation of sound transmission through solid walls, e.g., of masonry, is a challenging building acoustics topic. For an adequate building design tool it is of great importance to take arbitrary geometrical and acoustical boundary conditions as well as the air–structure interaction into account. Here, a model based on the finite element method is presented for the calculation of sound propagation in layered air/wall/fiber systems. The structure-borne sound is, on the one hand, influenced by the bending waves and, on the other hand, by the in-plane waves, if also the flanking transmission is investigated, where the bending waves are modeled by the Mindlin plate theory and the in-plane waves by the dynamic elastic disk equation. The acoustic behavior of air is described by the Helmholtz equation. The fluid–structure interaction is performed by using the principal of virtual work, and, as a final result, a completely coupled methodology is derived which allows the determination of sound fields and of the transmission loss of conventional solid walls. Numerical results are compared with measured values and the influence of various parameters is studied.
A high-frequency theory for thermo-viscoelastic beams
Authors: Altay G. Askar , Dokmeci M. Cengiz
Published: February 2014

To predict the macromechanical response of beams of uniform cross section, a system of 1-D equations is consistently formulated in both differential and variational forms within the frame of the 3-D theory of thermo-viscoelasticity. First, the basic equations of linear, nonisothermal 3-D theory of thermo-viscoelasticity are expressed in terms of the Laplace transformed field variables by a recent variational principle [Altay and Dokmeci, Acta Mech. 143, 91–111 (2000)]. Next, the temperature increment and displacement fields are expressed by the series expansions of the aerial coordinates of beam cross section. Then, a system of higher-order beam equations is derived by means of the variational principle together with the series expansions of field variables. The system of equations governs the extensional, flexural, torsional, as well as coupled vibrations of thermo-viscoelastic beams at both high and low frequencies. Certain cases involving special types of vibrations, geometry, and material properties are recorded. The uniqueness is investigated in solutions of the system of beam equations. [Work supported in part by TUBA.]
An energy finite element formulation for high-frequency vibration analysis of plate structures subjected to heavy fluid loading
Authors: Zhang Weiguo , Vlahopoulos Nickolas
Published: February 2014

An energy finite element formulation for computing the high-frequency behavior of plate structures in contact with a dense fluid is presented. The heavy fluid loading effect is incorporated in the derivation of the governing differential equations and in the computation of the power transfer coefficients between plate members. The validity of the new formulation is demonstrated through comparison to an analytical solution and to results computed by conventional finite element models comprised by a large number of elements. The influence of the heavy fluid on the dynamic response of two marine structures is identified by comparing results computed with and without the effect of fluid loading. The impact of the heavy fluid loading on the computation of the power transfer coefficients is also identified. [Research supported by the Michigan Seagrant.]
2.5-D FEM for cochlear-based transducers: Theory and experiment
Authors: Dodson John M. , Grosh Karl
Published: February 2014

The mammalian cochlea is an extraordinary organ exhibiting outstanding sensitivity and frequency discrimination capabilities. This tiny organ senses acoustic input via a coupled pressure-displacement wave along a pair of ducts separated by a partition known as the basilar membrane (modeled as a variable impedance plate) which exhibits spatial-frequency dependent resonances. The cochlea provides a template for designing devices which utilize this unique mode of transduction and holds potential for a new class of transducer. A reduced-order hybrid analytical/finite-element method (FEM) is used to allow computation of this coupled fluid-orthotropic variable width plate interaction problem. In this method, a 3-D FEM problem is reduced to 2-D discretization by utilization of a limited set of analytical pressure/structural modes orthogonal to the direction of wave propagation. Simple and complex assumed structural mode shapes were investigated to predict the plate response. Comparison to experiments revealed that the deflection of plate supporting structures is important to achieve a good correlation between theory and experiment. The validation program was conducted for isotropic and orthotropic plates mounted on a fluid-filled duct excited by a shaker-driven piston. Design studies for a cochlear-based transducer will be presented.
Dynamic response of in vacuo prolate spheroidal shells excited by surface force fields
Authors: Hayek Sabih I. , Boisvert Jeffrey E.
Published: February 2014

The equations of motion for nonaxisymmetric vibration of prolate spheroidal shells of constant thickness were derived using Hamilton’s principle. The thin shell theory used in this derivation includes three displacements and two changes of curvature. The effects of membrane, bending, shear deformations, and rotatory inertias are included in this theory. The resulting five partial differential equations are self-adjoint and positive definite. The shells are excited by axisymmetric line forces. The axisymmetric modal solutions are expanded in an infinite series of comparison functions. These include associated Legendre functions in terms of the prolate spheroidal angular coordinate. Numerical results for the frequency response were obtained for several shell thickness-to-length ratios ranging from 0.005 to 0.1, and for various diameter-to-length ratios, including the limiting case of a spherical shell. Sample mode shapes were obtained at selected resonant frequencies. [Work supported by ONR and the Navy/ASEE Summer Faculty Program.]
Adaptive procedures in psychoacoustics and speech research
Authors: Leek Marjorie
Published: February 2014

Over the past 30 years, adaptive procedures have become ubiquitous in psychoacoustic and speech perception research. The increasing use of these procedures may be traced in part to Harry Levitt’s paper describing the flexibility of up–down testing methods to determine the point on a psychometric function associated with a given level of performance [H. Levitt, J. Acoust. Soc. Am. 57, 55–62 (1971)]. Most psychoacousticians have, at one time or another, consulted this article to inform their experimental procedures. However, Harry’s contributions to psychometric testing do not begin or end with the publication of this seminal article. Here I will discuss the far-reaching impact of the transformed procedures that formed the basis of the 1971 article, point out some caveats to be considered when using these methods, and review other developmental work that Harry has accomplished to improve psychometric testing, including adaptive methods of fitting hearing aids and of testing speech recognition. [Work supported by NIH (DC00626).]
Harry Levitt and hearing aids
Authors: Allen Jont B.
Published: February 2014

Levitt has always been interested in technology transfer. In 1980 he became a proponent of digital hearing aids and fitting systems. I first got to know Levitt during the 1983 AT&T venture into a multiband compression hearing aid, proposed to Waldhauer by Villchur, based in the ideas of Steinberg and Gardner (1938). One of the first things we did was to visit Levitt and pepper him with questions. He saw it as a huge opportunity, but it was difficult because he was consulting for Nicolet. Eventually AT&T decided to return to its ‘‘core’’ business, and the venture was sold to Resound Corp. At CUNY we also developed the loudness growth in 1/2 octave bands (LGOB) test, which was popular at one time. Soon after, Levitt convinced me to port our research distortion product analyzer, called CUBeDIS, to the PC platform. It was then further developed by Jeng (Levitt’s student), and is presently Starkey’s DPOAE/TOAE DP-2000 infant hearing screener. All this technology transfer would not have taken place if it were not for Harry Levitt—so for that we must graciously thank him.
Acoustic and psychoacoustic benefits of adaptive compression thresholds in hearing aid amplifiers that mimic cochlear function
Authors: Goldstein Julius L. , Valente Michael , Chamberlain Roger D.
Published: February 2014

Automatic gain control of linear amplifiers dominates advanced hearing aid design, and has been extensively studied [Levitt et al., IEEE (1980); Dillon, Ear Hear. 17, 287–307 (1996)]. The normal cochlea uses essentially nonlinear, rapidly compressive amplification under efferent control [Kiang et al., Hear. Res. 22, 171–182 (1986); Robles et al., J. Acoust. Soc. Am. 80, 1364–1374 (1986)], whose salient characteristics have been modeled [Goldstein, Hear. Res. 49, 39–60 (1990)] and are presently adopted for multichannel hearing aids. Signal transduction in each channel is linear at low and high sound pressure levels (SPL), and smoothly joined by a compressive range. The transition from linear to compressive response at low SPL is controlled by an adaptive compression threshold, whose quiescent level provides the gain needed for weak sounds. For sustained sounds at higher SPL the compression threshold adapts upwards, providing effectively linear response and better acoustic quality for speech in noise. Pilot psychoacoustic experiments with a design simulation demonstrated that both normal and impaired hearing subjects perceive the improved quality, and comprehend speech in noise at least as well as with advanced hearing aids [Valente et al., J. Am. Acad. Audiol. 9, 342–360 (1998)]. [Work supported by NIDCD.]
Speech intelligibility and listener preferences for amplitude-compressed speech: Speech-based STI predictions and measurements on listeners with simulated hearing loss
Authors: Rosengard Peninah F. , Braida Louis D. , Payton Karen L.
Published: February 2014

Relations between objective intelligibility scores, subjective pleasantness ratings, and estimates of the STI for speech processed by multi-band amplitude compression systems were studied in normal-hearing listeners with simulated hearing loss. STI estimates were based on modulation spectrum changes in the processed speech signals [Payton and Braida, J. Acoust. Soc. Am. 106, 3637–3648 (1999)]. Linear amplification and two syllabic compression conditions were tested with and without two backgrounds: Speech-spectrum noise and restaurant babble. Signals were compressed independently in four nonoverlapping frequency bands with compression ratios of two and three, and attack and release times of 20 and 200 ms, respectively. The NAL-R formula determined output frequency-gain characteristics. Flat, 50 dB, sensorineural hearing losses were simulated in normal-hearing listeners via multiband expansion [Duchnowski and Zurek, J. Acoust. Soc. Am. 98, 3170–3181 (1995)]. Speech intelligibility and pleasantness ratings were obtained. All conditions were also evaluated using the modified STI. The STI predicted speech in restaurant babble would be more intelligible than speech in noise for each compression condition. The data reflected this for the two compression conditions. The STI predictions were also consistent with pleasantness ratings: Linear amplification was the most pleasant compression condition. [This work supported by NIDCD.]
Recent advances in audio and video text-to-speech synthesis
Authors: Syrdal Ann K. , Ostermann Joern , Cosatto Eric , Graf Hans Peter
Published: February 2014

Harry Levitt characteristically combines a statistical or data-driven engineering approach with extensive scientific knowledge when tackling fundamental research questions (such as how to measure co-articulation) and practical problems (such as evaluating intelligibility). Some of Harry’s expansive research interests and contributions have focused on audio and video text-to-speech (TTS) synthesis. Some major recent improvements in these technologies that have resulted from applying similar approaches are discussed. The unit selection method of synthesis described differs from both the earlier techniques of formant synthesis and of concatenative synthesis from a diphone inventory. In unit selection synthesis, speech or video units are selected from among multiple candidates in a large database by optimizing a cost function. The cost functions used for unit selection are estimates of perceptual distances. The improvement in naturalness for both audio and visual TTS achieved through the unit selection technique is demonstrated, and some of its current limitations and future work needed in this area is discussed.
Adaptation algorithms for noise reduction in hearing aids based on auditory models
Authors: Kollmeier Birger , Tchorz Jürgen , Wittkop Thomas , Hohmann Volker
Published: February 2014

Noise reduction algorithms for hearing aids usually employ certain assumptions about the ambient noise and the target (speech) signal that are only met in certain acoustical situations. In order to reduce unwanted artifacts whenever the acoustical real-life situation does not meet these assumptions, two approaches are introduced and tested that classify the acoustic environment. Both approaches are motivated by auditory models and are used to control the parameters of noise-reduction schemes. The first approach uses the amplitude modulation spectrogram (AMS) in combination with a neural net to estimate the speech-to-noise ratio either on the broadband signal or within narrow bands. It can be used for single-channel (i.e., monaural) noise reduction even for fluctuating background noise and unfavorable signal-to-noise ratios. The second approach derives the ‘‘degree of interaural coherence’’ from the input signals to both ears that decreases with increasing reverberation and increasing number of active sound sources. It is combined with several binaural noise reduction techniques, i.e., directional filtering, dereverberation, and adaptive beamforming. The advantage of using these approaches will be presented and discussed on the basis of speech intelligibility and subjective quality assessment data.
Developmental changes in GABA expression across metamorphosis
Authors: Simmons Andrea M. , Horowitz Seth S. , Chapman Judith A.
Published: February 2014

Gamma-aminobutyric acid (GABA) expression in the developing brain has been implicated in factors such as process outgrowth, cell proliferation, cell migration, and synaptogenesis. Immunofluorescent staining techniques were used to characterize changes in GABA distribution in medullary and cerebellar regions of the bullfrog’s brainstem across metamorphosis. Auditory and vestibular nuclei show profound developmental changes in distribution; the cerebellum and cerebellar nuclei show little change, being strongly stained at all stages examined. In early stage tadpoles, the dorsolateral nucleus (DLN), vestibular nucleus (VN), and anterior lateral line (LLa) nucleus show widespread punctate and diffuse label, but few discrete GABAergic cells. Little or no staining is observed in the superior olivary nucleus (SON). This basic pattern persists until just before metamorphic climax stages, when discrete GABAergic cells first begin to appear in the SON; more discrete cell staining is also visible in the DLN and VN. At metamorphic climax, the DLN, VN, and SON show clear populations of GABAergic cells. In postmetamorphic froglets and adults, GABAergic cells and GABA-labeled fibers exist in sharply delineated regions of these nuclei, with limited diffuse/puncta label. These changes are consistent with the idea that GABA plays important roles in regions of the brainstem undergoing developmental transformation.
Thyroid hormone influences on the development of auditory function in mammals
Authors: Walsh Edward J. , McGee JoAnn
Published: February 2014

The essential role of the thyroid hormone in development is one of the most clearly established principles of biology. Although its importance as a factor affecting the maturation of the inner ear is unquestionable, the precise mode of its actions and the identity of its intracochlear targets remain issues of conjecture. Although both alpha1 and beta forms of the thyroid hormone receptor (TR) are expressed in the developing cochlea of mammals, permanent auditory deficits occur only when TR-beta1, which is distributed widely in the brain and inner ear, is defective. The presence of multiple forms of thyroid hormone receptors with different functions suggests that the mode of thyroxins action in the inner ear is complex. When thyroxin is unavailable during development, as in Tshr (hyt) mutant mice or animals rendered hypothyroid by treatment with goitrogens, a distinctive constellation of functional deficits are observed, suggesting that the primary, enduring locus of pathology lies within the domain of the cochlear amplifier. We will discuss the physiological basis underlying this position and propose a mechanism that accounts for the phenomenon, as well as the wide range of anatomical abnormalities that have been observed in the cochleae of hypothyroid mammals. [Work supported by NIDCD grant DC00982.]
Neural representation and perception of speech sounds in children with learning problems
Authors: Kraus Nina , King Cynthia
Published: February 2014

An inability to process auditory information, especially speech, characterizes many children with learning and attention problems. These speech–sound perception problems may arise, at least in some cases, from faulty representation of the speech signal in central auditory centers. Our working hypothesis is that acoustic–phonetic disorders are abnormalities in preconscious neurophysiologic representation of sound structure by central auditory pathway neurons and is reflected by subcortical and cortical aggregate neural responses. Brainstem and cortical potentials (ABR, FFR, cortical P1/N1/N2, MMN) reflect activity from different anatomic sources and represent different aspects of auditory function. An obvious characteristic distinguishing these responses is their development time course. Results indicate that while normal and learning impaired children do not differ in auditory system development per se, they develop different listening strategies which affect the neural representation of sound structure along the auditory pathway. [Work supported by NIH RO1 DC 01510.]