bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of occupancy evaluation of the multifamily housing sound environment
Authors: So Michiko , Kimura Sho , Inoue Katsuo
Published: October 2005

Single-family wooden dwellings have formed the mainstream of housing in Japan because of climatic conditions. However, multifamily housing began a rapid and widespread expansion beginning in the mid-1960s as one mode of housing and currently accounts for a proportion exceeding conventional single-family dwellings, especially in major urban centers. In order to gain an understanding of the current conditions of environment performance of multifamily housing, an extensive questionnaire survey was conducted targeting the residents of 16 housing estates, all of recent construction and considered to have multifamily housing architectural properties standard in Japan at the present time. To summarize the results, there was an overall indication of a high evaluation of satisfaction with current housing. Meanwhile, regarding the desire for improvements or rebuilding within current housing, there is a greater demand for ‘‘dampness proofing’’ and ‘‘sound insulation.’’ In addition, the percentage of dwellers who felt dissatisfied with the sound environment as an actual sensation in their everyday lives accounted for approximately 30% in each of the public housing complexes. Overall, ‘‘noise in the surrounding environment is terrible’’ and ‘‘sound from the floor above is extremely loud’’ were given as the primary reasons for this.
Aircraft noise problems and solutions at Logan International Airport
Authors: Timmerman Nancy S.
Published: October 2005

Aircraft from Logan International Airport cause noise in the surrounding communities from overflights (arrivals and departures), take-offs, landings, run-ups, and taxiing. Some surrounding communities are as close as 900 ft from the centerline of an active runway. Methods of minimizing noise impact from aircraft in the communities include: preferential nighttime runways, standard instrument departures which maximize open spaces, restrictions on types of nighttime operations, restrictions on locations and times of ground noise generation, and enforcement of these restrictions. In addition, the airport monitors the noise in the communities (continuously and by request), receives and replies to complaints, and has a soundproofing program for eligible residents. The airport has just started monitoring flight deviations from standard departure procedures. Examples will be drawn from these topics.
Remote area monitoring for noise mitigation
Authors: Lee Robert A.
Published: October 2005

The USAF has been required to conduct noise measurements to assess the impact of its flying mission. In 1984 as part of a Record of Decision to fly super-sonic flights over Valentine, Texas and Reserve, New Mexico, the USAF had to conduct sonic boom monitoring that cost over $1.5M. Validation studies have been conducted to increase the public’s confidence in the noise models used for the Air Force Air Installation Compatible Use Zone program. In 1992 the USAF developed a noise monitor that could be put around the neck of an animal for studies to determine the effects of military overflights on wildlife. The USAF has started a new development program to consolidate all of its noise measurement requirements into a remote monitoring package. This package will use different sensors and data compression for various measurements but the same radio transmitter hooked to a long haul communications system to transmit the data back to a remotely located computer system for analysis. This capability will allow the USAF to do real-time monitoring of noise impacts for determining its mitigation effectiveness.
Assessing sonic boom structural damage potential using structural-acoustic simulations
Authors: Garrelick Joel M. , Martini Kyle
Published: October 2005

The responses of a number of structures to sonic booms were obtained with dedicated flyovers and by means of both direct and reciprocal structural-acoustic simulations. The overall objective was to develop a cost-effective technique for assessing damage potential. Test results are briefly outlined in this paper. Methods and difficulties relating the measured response functions to the available damage criteria database are described. For one of the (sub)structures, an external window, both the strain and acceleration were recorded. Thus the tests provided an opportunity, under reasonably controlled conditions, for evaluating the practical applicability of Hunt’s findings regarding the relation between peak strain and velocity in forced, resonant, simple structures [J. Acoust. Soc. Am. 32, 1123–1127 (1960)]. The limiting effects of uncertainties in defining the resonant mode type and shape and material parameters that are required to implement the relationship are discussed. [Work sponsored by Armstrong Lab., WPAFB, U.S. Air Force.]
Control of construction noise from large-scale infrastructure projects
Authors: Wong C. L. , Chung Albert Y.-K. , Tai Daniel M.-K.
Published: October 2005

Since early 1990s Hong Kong has set into motion ten major Airport Core Programme Projects under the Port and Airport Development Strategy. These integrated infrastructure projects, which were planned for completion in 1997, are comprised of a replacement airport on an island, 1669 hectares of reclaimed land, a new harbor crossing and land tunnels, new towns, a 34-km airport railway and over 30 km of expressways, and the world’s longest road/rail suspension bridge. The scale, scope, and speed of these construction projects are probably the greatest in the world to date. The potential noise impacts from round-the-clock construction activities have been a significant issue for this densely populated city where many of the residents are only tens of meters away from the sites. The relentless pressure to proceed quickly with the projects despite early slowdowns due to initial political uncertainties on the Strategy have added constraints and complexities in implementing control measures against the impacts. This paper covers the implementation aspects of the Environmental Impact Assessment carried out, the monitoring role of the specially set up Environmental Protection Offices, the statutory control of construction noise under the Noise Control Ordinance, and, finally, selected case studies on noise mitigation measures applied.
Reaction to the outdoor noise among inhabitants in Nagoya, Japan and Beijing, China
Authors: Mishina Yoshiaki , Oishi Yasaki , Hayashi Akinori , Kuno Kazuhiro , Okumura Yohzoh , Da Rui Zheng
Published: October 2005

Inhabitants’ reaction to outdoor noise in Nagoya and in Beijing was surveyed. A questionnaire on noise was conducted with more than 2000 people in Nagoya and more than 1000 in Beijing. They were also asked whether they were sensitive to each of the 37 types of noise sources. The responses of inhabitants to the above questionnaire in Beijing are more sensitive than those in Nagoya to loudness, annoyance, and sleep disturbance. Road traffic noise is the most audible of 37 noise sources in both cities. Sounds of fireworks and sounds from festivals are also highly audible in Beijing. The most annoying noise is one from motorcycle gangs in both cities, and one from construction in Beijing. The annoyance rates in Beijing are higher than those in Nagoya.
The investigation of the internal acoustic properties of a high voltage arc in water
Authors: Fisher David L. , Rogers Robert L.
Published: October 2005

The internal structure of the arc phase of a high-voltage discharge in water is characterized by the evolution of water molecules into atomic and ionic components. However, the spatial distribution of these components, in addition to the temperature, vary considerably due to the influx of mass at the bubble boundary. The physical and acoustical properties of this bubble are investigated through the use of a newly developed nonlinear 1-D fluid code. The model includes dissociation and ionization (through +2 for oxygen), thermal conduction, mass influx due to blackbody radiation at the bubble boundary, and a complete electrical model which includes the calculation of the electrical resistivity of the bubble due to both neutrals and ions. Preliminary results show interesting acoustical phenomena including strong acoustical pulses bouncing inside the bubble. These shock waves reflect off the bubble boundary, forming an inward propagating wave not unlike that of an implosion. The nonlinear inviscid fluid equations are also used to evolve the water exterior to the bubble boundary. [Work supported by the Office of Naval Research.]
Sonochemical reactions at reduced pressure: A possible stage for the transition between different bubble dynamics
Authors: Hayashi Shigeo , Kokubun Takao
Published: October 2005

The concentration of dissolved oxygen in water at pressures in the range from 0.1 to 1 atm was determined by Winkler’s method in order to elucidate previous results on the sonochemical oxidation of potassium iodide, where the reaction rate slowed down at some critical pressures that depended on the ambient gas. The concentration was found to be nearly proportional to the pressure, but the concentration relative to saturation varied depending on the method of pressure control. Further evidence for different dynamics below and above the critical concentration was that the tone of cavitation noise changed around there. Assuming that the density of cavitations is proportional to the gas concentration, it is suggested that the cavitation bubbles are relatively stable in the low-density regime, since their mutual interaction is weak. Above some critical density, however, the bubbles may interfere with one another, inducing the implosion at a moment earlier than that for the minimum bubble size achieved in the low-density regime. This high-density behavior results in the decrease of the reaction rate, and should usually be seen in the conventional sonochemistry, where high-power ultrasounds are employed. It is also suggested that, as the pressure is varied, single bubble sonoluminescence may be similarly affected.
Effect of the sonication condition on the generation of free radicals by ultrasound
Authors: Yanagida Hirotaka , Minagawa Keiji , Ogata Tateaki , Takimoto Jun-ichi , Koyama Kiyohito
Published: October 2005

There have been many reports on chemical reactions using ultrasound such as decomposition of polymer chains or initiation of polymerization by ultrasound. However, the mechanism of these sonochemical reactions has not been clarified yet. Understanding the mechanism will be useful for establishing a new radical polymerization system without an initiator, for new applications in the medical field, and so on. Decomposition of water (H2O) into OH and H radicals is being studied by high-intensity ultrasound, because it is one of the simplest systems used for elucidation of the mechanism of sonochemical reactions. The influence of sonication conditions such as ultrasonic frequency, sonication time, and ultrasonic intensity on the production of OH radicals from water was studied, and the factors governing the sonolysis were examined. Since the OH radical is very short lived, DMPO (5,5-dimethyl-1-pyrroline N-oxide) was used as a scavenger, and the concentration of spin-trapped OH radicals was measured by ESR after sonication. The results show that (1) lower frequency ultrasound generates the radicals more efficiently, (2) the radical concentration initially increases linearly with time and the ultrasound intensity, and then (3) saturates at a value which is independent of the ultrasound intensity.
Experimental investigations of the acoustic backscattering of a single cavitation bubble
Authors: Niederdränk Torsten
Published: October 2005

There is great interest in the oscillation of a single cavitation bubble in a sound field. The dynamic bubble behavior is investigated by means of the acoustic backscattering of a high-frequency ultrasonic field. An experimental setup for generating single bubble cavitation is used. In addition to the driving sound field of low frequency (25 kHz) for generating the single cavitation bubble in a piezoelectric tube, a second high-frequency image sound field is radiated into the cavitation cell by a focusing PVDF transducer. The high-frequency components are scattered by the bubble and can be received by the same PVDF transducer, assuming that the bubble is placed in the focus of the transducer. For the image excitation, bursts have been used with a frequency of 30 MHz and a burst length of 20 μs. The amplitude of the scattered sound depends on the temporary bubble radius. In the backscattered signal, a slight shift appears in the frequency due to the fast motion of the bubble wall. After considering the scattering behavior of a bubble theoretically, the setup for the experimental investigations and some results are presented.
Acoustic spectroscopy of surfactant micellar solutions
Authors: Stribulevich A. L.
Published: October 2005

The acoustic and structure-dynamic properties of decylpyridinechloride (DPCI) aqueous solutions at concentrations of 0.06–2.0 mol/l were investigated using acoustic and rheologic methods. Sound spreading rate and absorption in the frequency range from 5 to 2500 MHz as well as density and shear viscosity coefficients in the temperature range of 283–353 K were measured. Based on experimental data obtained, a number of acoustic parameters for aqueous solutions, such as bulk to shear viscosity ratio and classical sound attenuation, were calculated. It was shown that in the solutions studied (as in the case with water) additional, in relation to classical, sound absorption is caused by structure reorganization (i.e., changes in arrangement of molecules, molecular associations, and surfactant-water complexes). The kinetic compensation effect was observed for reactions of intermolecular bond tearing. The mechanism for micellar formation is proposed. For the DPCI aqueous solutions at concentrations lower than 0.2 mol/l acoustic relaxation is not observed, whereas in the case of more concentrated solutions the predominant mechanisms for acoustic relaxation are intermicellar interaction and micellar aggregates formation. The lack of a hydrocarbon conformational transition region in the acoustic spectra gives one grounds to assume that the micellar core is structurized and possesses the properties inherent to crystalline hydrocarbons.
A further development of underwater near-field acoustical holography: Toward a more quantitative measurement technique
Authors: Yoshikawa Shigeru , Saijyou Kenji
Published: October 2005

Near-field acoustical holography (NAH) is a strong experimental tool, which allows the visualization of the underlying physics in structural vibration, radiation, and scattering. NAH technology has been extending the scope of its application by algorithmic and experimental adaptations. However, it is recognized that NAH leaves behind some problems arising from the spatial FFT processing if one tries to extract more quantitative information for structural analysis. For example, it is not as easy to estimate the reflection coefficient of a rib attached on a plate as accurately as it is with the NAH measurement. Also, the precision in reconstructing the structural intensity seems to be relatively low. New methods to reconcile these difficulties are proposed in this paper: One is an ‘‘extrapolation method’’ to reduce the errors due to wraparound and zero padding; the other is an ‘‘adaptive K-space window method’’ to choose the maximum wave number of the measured evanescent wave depending on the differentiation order in the equation of the structural intensity.
Presidential address: Acoustical Society of America—2016
Authors: Apfel Robert E.
Published: October 2005

The president presents his vision for the future of the Acoustical Society and its publications. This address was presented at the Plenary Session of the ASA Spring Meeting in Indianapolis, Indiana on 15 May 1996.
Age- and gender-specific reference ranges for hearing level and longitudinal changes in hearing level
Authors: Morrell Christopher H. , Gordon-Salant Sandra , Pearson Jay D. , Brant Larry J. , Fozard James L.
Published: October 2005

This paper presents age-specific reference ranges for hearing level and change in hearing level for men and women at 500, 1000, 2000, and 4000 Hz. The percentiles are constructed from data obtained from persons in the Baltimore Longitudinal Study of Aging who were rigorously screened for otological disorders and evidence of noise-induced hearing loss. The resulting percentile curves represent norms for changes in hearing level in the absence of any known otologic disease. These percentile curves provide a reference for detecting when a person deviates from a normal pattern of change, thus helping in diagnosing problems with hearing or in monitoring hearing in occupational settings. The smoothed means and standard deviations of the hearing levels were used to construct the longitudinal percentiles. The percentiles for cross-sectional change were constructed using the skew normal distribution to allow for the percentiles to be asymmetric on either side of the median level. These percentiles are the first reference curves that (1) provide standards for hearing level changes over periods of up to 15 years, (2) account for age differences in the distribution of hearing levels, and (3) are based on data from persons who have been systematically screened for otological disorders and evidence of noise-induced hearing loss.
Effects of a sediment scattering layer in underwater-acoustic studies of intensity sensitivity and data matching
Authors: Howell K. J. , Jacobson M. J. , Siegmann W. L. , Carey W. M.
Published: October 2005

A scattering layer is introduced at a horizontal water–bottom interface to account for effects of attenuation due to bottom volume scattering. Using a wide-angle parabolic equation, a formula for the local mean intensity level is found for a shallow-ocean model consisting of three isospeed fluid layers: water, scattering layer, and bottom. The sensitivity of the theoretical mean to environmental parameters is studied, and the standard deviation of intensity is examined also. Comparisons are made between intensity statistics of the three-layer model and of other isospeed models. Also, comparisons are made between three-layer model statistics and data from a recent New Jersey Shelf experiment. Results from the inclusion of a scattering layer for the prediction of relative intensity statistics are evaluated over a wide range of acoustic frequencies. It is found that, with parameter values representative of the experimental site, the three-layer model can successfully match the local mean and standard deviation of the intensity data.
An analysis of wave dispersion in coarsely laminated symmetric composite plates
Authors: Kim Michael , Hwang Y. F.
Published: October 2005

The elastic wave phenomena in a multilayer composite plate of arbitrary layers of elastic and viscoelastic materials with or without fluid loading are discussed in this article. Emphasis is placed on understanding the peculiar dispersion behaviors due to the extremely nonuniform material property and damping among the layers. Classification of the types (or modes) of wave propagation is accomplished by analyzing the dispersion curves, detailed modal patterns (that show the relative motions along the thickness of the plate), and strain energy distributions among the layers. A three-layer sandwich, elastic/viscoelastic/elastic, composite plate is used as a numerical example. The calculated dispersion curves are displayed in a frequency–phase speed plot and, sometimes, accompanied by a wave number–frequency plot as an aid to understanding the wave phenomena significance of structural acoustics. The major differences between the dispersion characteristics of the sandwich plate with a soft core and that of a uniform solid plate are identified and reasons for the differences are provided. Effects of the core material properties, such as the amount of damping on the wave dispersion characteristics, the propagating wave modal structures, and other factors of structural acoustics significance of a sandwich plate, are discussed. The dispersion curves calculated from the analytical method based on the elasticity theory show good agreement with results calculated independently by the finite element method.
Measurements of the narrow-band decay rates of a gas/particle suspension confined in a cylindrical tube: Relationship to particle concentration
Authors: Moss Simon H. O. , Attenborough Keith
Published: October 2005

A novel method which uses reverberant decay rates to measure the concentration of solid particles suspended in a gas has been investigated. The impulse response, measured across a section of cylindrical tube containing the suspension of particles with mean diameter 6 μm, was processed to determine the reverberant decay rates of selected frequency bands. The decay rates, observed with and without suspended particles, were used to give a value of excess decay rate in several frequency bands. The excess decay rates are found to vary linearly with the particle concentration. The frequency range used was 1.5–20 kHz, and the particle volume concentration was varied between 0–12 parts per million (ppm).
Dynamic self-consistent analysis for elastic wave propagation in fiber reinforced composites
Authors: Kim Jin-Yeon
Published: October 2005

A dynamic self-consistent method previously proposed and validated for composites containing spherical inclusions is applied to the simplest two-dimensional problem: SH wave propagation in unidirectional fiber reinforced composites. The self-consistent conditions for SH waves are derived and the effective wave speed and coherent attenuation are calculated numerically for five different composites. For two composites showing very different dynamic behaviors, the results of the present theory are compared with those of multiple scattering theories and another self-consistent theory. At low volume fractions the present theoretical results coincide with those of the multiple scattering theory using exact pair-correlation functions, whereas the results based on another self-consistent theory deviate markedly from the others. As the volume fraction increases, the three theories give different results although they have qualitatively similar trends. The present theoretical results for composites considered in this article exhibit less dispersion and physically realizable attenuation. An important observation is that the multiple scattering theory predicts vanishingly small attenuation at low frequency when volume fraction is high. Experiments over wide ranges of frequency and volume fraction are needed in order to assess the accuracy and validity of the present theory.
On sound scattering and attenuation of Albunex® bubbles
Authors: Ye Zhen
Published: October 2005

In this paper, the theory of wave scattering by shelled scatterers is employed to study ultrasonic scattering by Albunex® bubbles. These bubbles are approximately gas-filled microspheres surrounded by a shell of human serum albumin that behaves collectively as a continuous, damped, elastic solid. An exact solution, written in terms of a modal series representing the contributions from various vibrational modes of the bubbles, is presented for the acoustic scattering function. Results are obtained from numerical computation and are compared with the previous results. It is shown that (1) at frequencies below or slightly higher than the resonance, acoustic scattering by Albunex bubbles is nearly omnidirectional and bears similarities to that by usual air bubbles, and the results agree with the previous results for these frequencies; (2) the resonance frequency for a given Albunex bubble tends to increase with the shear modulus of the elastic shell which, however, appears to have little effect on acoustic scattering at high frequencies or from large bubbles; (3) acoustic scattering by Albunex bubbles seems not sensitive to the bulk modulus in the shell for a wide range of frequency and bubble size. The results also reveal that the scattering by Albunex bubbles can be highly anisotropic when the frequency is somehow above the resonance, and the previous theories solely based on the radial pulsation of the bubbles overestimate the sound scattering cross section in this case. In addition, some inconsistencies in the previous results are addressed. Furthermore, the forward scattering theorem is used to study the acoustic attenuation by Albunex bubbles. According to this theorem, the acoustic extinction cross section is related to the imaginary part of the scattering function in the forward direction. The forward scattering function is calculated and compared with the backward scattering function. The results show that the scattering function in the two directions can differ significantly from each other under certain conditions.
Design criteria for the damping effectiveness of structural fuzzies
Authors: Maidanik G. , Dickey J.
Published: October 2005

A rudimentary statistical energy analysis (SEA) of a structural fuzzy reveals that an adjunct structure, i.e., the ‘‘fuzz’’ in a structural fuzzy, attached to a master structure for the purpose of increasing the loss factor of the union, in the range of frequency of concern, is required to satisfy three design criteria. A brief statement of these design criteria is made. An analytical rendition is also presented to give the statement qualitative definition and assessment. Possible noise control issues impacting the performance of structural fuzzies are raised.
Ultrasound fields from triangular apertures
Authors: Jensen Jo/rgen Arendt
Published: October 2005

The pulsed field from a triangular aperture mounted in an infinite, rigid baffle is calculated. The approach of spatial impulse responses, as developed by Tupholme and Stepanishen, is used. By this both the emitted and received pulsed ultrasound field can be found for any transducer excitation and electromechanical impulse response. The continuous wave field is also readily obtainable through a simple Fourier transform. The spatial impulse response is calculated without approximation, and the solution is valid in the half-space in front of the aperture for a homogeneous, nonattenuating medium. The solution can be used in finite element programs for calculating fields from arbitrary transducer geometries.
Modeling sea surface scattering by the time-domain finite-difference method
Authors: Stephen Ralph A.
Published: October 2005

A numerical scattering chamber based on the time-domain finite-difference solution of the two-way elastic wave equation is applied to a sea surface scattering problem, and excellent agreement is obtained in amplitude and phase with a reference solution obtained by an integral equation method. The sea surface roughness is one representation of a Pierson–Moskowitz spectrum for a wind speed of 15 m/s. The incident field is a 400-Hz continuous wave generated by a Gaussian tapered vertical array. This problem demonstrates a number of issues in numerical modeling of wave scattering. The spreading of Gaussian beams, even in homogeneous media, creates an asymmetry in the insonification of the surface footprint or scattering area. Because of beamspreading, Gaussian tapered vertical arrays do not generate Gaussian beams. Scattering from a rough, free, fluid surface can be accurately solved with careful treatment of the numerical boundary representing the free surface. Continuous wave (cw) scattering problems can be solved in the time domain. For the second-order, explicit, staggered finite-difference formulation used in this study, a spatial sampling of 20 points per acoustic wavelength was necessary for acceptable grid dispersion. However, to correctly compute the scattered field for the test model, it was sufficient to specify the free surface at a spatial sampling of only ten points per acoustic wavelength.
On the measurement of modal group time delays in the deep ocean
Authors: Brown Michael G. , Viechnicki John , Tappert Frederick D.
Published: October 2005

The modal description of sound propagation in deep ocean environments is considered. Recently published inversion algorithms have assumed that modal group time delays can be measured. Such a measurement is straightforward to make if either: (1) the modal group arrival of interest is resolved in time; or (2) the wave field is sampled on a dense vertical array which spans much of the water column, thereby enabling the orthogonality of the modes to be exploited. In order to temporally resolve modal group arrivals using measurements made on a single hydrophone, the frequency bandwidth must: (a) be sufficiently broad that the temporal separation between successive modal arrivals exceeds the reciprocal bandwidth; and (b) be sufficiently narrow that, across the band, the group slownesses of neighboring mode numbers do not overlap. To satisfy both conditions [(a) and (b)] the ratio of the range to the center frequency must be large. Unlike ray arrivals, modal group arrivals broaden as range increases due to dispersive spreading. To minimize dispersive spreading so that accurate group delay time estimates can be obtained, the ratio of range to center frequency should be kept small. Thus the requirements for temporally resolving modal group arrivals conflict with the conditions that minimize dispersive spreading. Numerical results are presented which give quantitative estimates of which combinations of range, center frequency, bandwidth, and mode number produce conditions which are favorable for temporally resolving modal group arrivals in six regions of the deep ocean at mid and low latitudes. These results suggest that it is extremely difficult to find conditions which allow modal group arrivals to be temporally resolved and simultaneously allow group delay times to be measured with sufficient accuracy to be useful for tomography. The situation is further complicated by internal waves which appear to cause mode coupling and significant broadening of modal group arrivals at frequencies above approximately 50 Hz. The combined effects of dispersive spreading and internal wave-induced mode coupling suggest that, without employing mode filtering techniques, modal group time delay-based inversion schemes in the deep ocean do not appear to be promising.
Propagation of surface waves in a prestressed piezoelectric material
Authors: Chai J.-F. , Wu T.-T.
Published: October 2005

In this paper, the Lothe–Barnett’s integral formalism is extended to solve the surface wave problem of a prestressed piezoelectric material. By using the electroacoustoelasticity, the effective material constants and the mass density in the prestressed initial state are determined, and then the surface wave velocities of a prestressed piezoelectric crystal can be obtained by the integral formalism. Under some limitations, the properties of the integral matrices derived in the Lothe–Barnett’s integral formalism are shown to be valid for the prestressed piezoelectric crystal. A computer program is implemented to calculate the surface wave velocities of a prestressed X-cut lithium niobate (LiNbO3) crystal. Finally, a possible application of the electroacoustoelastic effect to the design of a delay-controllable delay line is proposed.
Energy dissipation in oscillating flow through straight and coiled pipes
Authors: Olson J. R. , Swift G. W.
Published: October 2005

The energy dissipation is reported for oscillating flow in U-shaped pipes with 180°, 540°, and 900° curves at the base of the U. Analysis permits separation of the dissipation in the straight and curved portions of the pipe. Using water, water/glycerine mixtures, liquid nitrogen, and helium gas, the dissipation was measured for fluid flow regimes (Reynolds number, quality factor, and pipe curvature) which have not previously been reported. Measured loss in the straight portion is compared to numerical solutions using a turbulent quasisteady representation of the wall shear stress. Measured loss in the curved portion is compared to simple theory. The results are applicable to thermoacoustic devices.
Ultrasonic 2-D SH probe modeling in anisotropic solids
Authors: Niklasson A. Jonas
Published: October 2005

In this paper, 2-D SH wave propagation and probe modeling in an anisotropic half-space is discussed. In deriving the equation of motion the assumptions are that the displacement is purely antiplane, that the problem is two dimensional and that the energy is transported purely in the plane. The probe, which is situated on the surface of the half-space, is modeled by the surface traction it is causing. An expression for this traction is obtained by modifying the traction of a plane wave. The wave propagation problem is then solved formally using Fourier transform techniques. The obtained expression is approximated for large distances from the probe using the method of stationary phase. Some numerical examples are presented which illustrate some of the properties of wave propagation in anisotropic solids.
A finite-difference scheme for elastic wave propagation in a circular disk
Authors: Cherukuri H. P. , Shawki T. G.
Published: October 2005

A second-order accurate, explicit finite-difference scheme is presented for the numerical solution of elastic wave propagation in a circular disk subjected to traction boundary conditions. One face of the disk is subjected to an axisymmetric loading while the remainder of the boundary is free of tractions. The temporal dependence of the forcing function is taken to be trapezoidal. The governing partial differential equations are discretized by using second-order accurate central difference schemes in both time and space. A stability criterion is analytically derived by using the classical von Neumann analysis. The numerical results are compared with the analytical results based on a modal analysis approach and the agreement is excellent until times as late as 60 μs where, the traversal time of a longitudinal wave across the thickness is approximately 4.5 μs. Furthermore, for time-dependent loading, the numerical results are compared with those from a corresponding mixed problem. Present results show that, even for time-dependent loading, the solution of the mixed problem provides a very accurate approximation to the solution of the nonmixed problem for sufficiently large distances in the axial direction.
Analytical solution of a condenser microphone model as an example of the mathematical treatment of coupled acoustic systems
Authors: Kainz Wolfgang
Published: October 2005

In this work an analytical model for a condenser microphone with a pattern of holes in the electrode is solved approximately by applying an operator method of quantum mechanics. Essential is the replacement of the operators corresponding to the Green’s functions of the cylinder in the fundamental integral equations of the system by products of identity operators times an appropriately chosen constant. The second approximation is the averaging of the holes and by replacing the effect of the holes in the electrode by a product of the identity operator times the part of the area of the small holes in the electrode compared to the whole area of the electrode. The last approximation is the replacement of the displacement of the fluid in the small holes by their mean value and the assumption of small holes compared to the total area of the electrode. By a summation method over zeros of Bessel functions it is possible to do infinite summations exactly and to provide an analytical solution of the average displacement of the membrane as a function of the frequency of the incoming plane wave. The approximations are justified by the good agreement with experiment.
Application of Hilbert space techniques and Green’s function methods to a realistic condenser microphone model
Authors: Kainz Wolfgang
Published: October 2005

A realistic model for a condenser microphone is theoretically investigated. The model consists of a rigid cylinder closed on the bottom by a membrane and on the top by a rigid plate. The cylinder is divided into two chambers by an electrode with a number of small holes. This coupled acoustic system is mathematically treated by an operator formalism. Each part of the system (outer space, membrane, electrode, two chambers) corresponds a linear operator in a Hilbert space. The interfaces (membrane, electrode with holes) correspond to state vectors in this Hilbert space. Applying Green’s integral formula leads to a system of equations in this space, corresponding conventionally to integral equations with Green’s functions as kernels. By approximating the operators of the two chambers by multiples of the identity operator (i.e., conventionally replacing the singular Green’s function by multiples of the Dirac delta function) it is possible to solve the problem analytically, taking into account exactly the pattern of the holes in the electrode, thus avoiding an approximation made in the preceding paper. The agreement with experiment is very satisfactory.
A comparison of three diffuse reflection modeling methods used in room acoustics computer models
Authors: Lam Y. W.
Published: October 2005

It is generally believed that partial diffusion will inevitably occur when sound is reflected off a real-life wall. Such diffusion may be caused by the finite size of the wall or by the unevenness of the wall’s surface geometry and/or impedance. Commonly used room acoustics prediction methods such as the image method or the ray-tracing method are usually based on a straight-line geometrically specular reflection model, which must be modified to account for this real-life partial diffusion in order to give realistic results. This paper investigates the problems of the diffuse-reflection coefficient that should be assigned to a wall in auditoria, and the prediction algorithm that may be used to model the diffuse reflections. Acoustic measurement results from scale models and a real multipurpose auditorium were used to compare with the prediction results from three models which used different methods of calculating diffuse reflections. The behavior of these prediction methods and the range of diffuse-reflection coefficients that may be used for different halls is discussed.
The dependence of diffusion parameters in a room acoustics prediction model on auditorium sizes and shapes
Authors: Lam Y. W.
Published: October 2005

The dependence of the calculation parameters that control the diffusion calculation in a room acoustics prediction computer model on auditorium sizes and shapes was investigated through a series of physical scale model experiments. Seven auditorium type scale models were used in total. The models had typical auditorium aspect ratios of around 2.5:1.8:1 and important auditorium features such as stage, balcony and raked seating. Their sizes varied from 5050 to 29 500 m3 and shapes included rectangular, fan, reversed fan, and hexagonal. The computer prediction model used a combination of randomized ray directions and secondary diffuse area source radiation to calculate diffuse reflections in its prediction of a room’s acoustic characteristics. The calculation process is controlled by two diffusion parameters: the diffuse-reflection coefficient of surfaces and a transition order which control the on-set of the diffusion calculation process. It was found that a diffuse-reflection coefficient of 0.1 was appropriate for the plain walls of the scale models in the 500- and 1-kHz octave bands, and this value did not change significantly with the scale models’ shapes and sizes. In the lower frequency bands the diffuse-reflection coefficient changed from 0.1 in the smaller scale models to over 0.4 in the larger models. A slight increase was also observed in models with more complicated shapes. For the transition order a low value (0) was found to be appropriate for the low frequency bands but a higher value (1 to 3) was required in the 500- and 1-kHz bands and also in situation where the specular/geometrical influence of a room was important. The average and root-mean-square prediction errors of the computer model using a generic set of diffusion parameters for the scale models were found to be, respectively, within 3% and 10% for RT, and 1.1 and 2 dB for sound level. For the clarity index C80, the prediction errors in the smallest model were within 1.9 and 2.2 dB, which were significantly higher than the 0.8 and 1.8 dB found in the other models.
Performance of high-rate adaptive equalization on a shallow water acoustic channel
Authors: Stojanovic M. , Proakis J. G. , Catipovic J. A.
Published: October 2005

Multipath propagation in underwater acoustic channels causes intersymbol interference in the transmission of digital communication signals. An increase of the transmission rate on a multipath channel results in longer intersymbol interference, which ultimately limits the performance of a phase-coherent digital communication system. Recent experimental results, however, show a seemingly surprising result: an increase in transmission rate resulted in improved system performance. An explanation for this phenomenon is found in the time variation of the ocean multipath. In strongly fluctuating shallow water channels, higher transmission rates allow for more frequent sampling of the rapidly varying channel, thus resulting in a better tracking capability of the receiver. Experimental results obtained in shallow water show a substantial improvement in performance of QPSK coherent detection over a 1-mile range, as the data rate is increased from 5 to 20 kilobits per second. A theoretical analysis based on stochastic channel modeling supports the experimental observations.
Statistical properties of spontaneous otoacoustic emissions in one bird and three lizard species
Authors: van Dijk Pim , Manley Geoffrey A. , Gallo Lothar , Pavusa Andrea , Taschenberger Grit
Published: October 2005

Spontaneous otoacoustic emissions were recorded in the barn owl Tyto alba guttata (five ears), and in three lizard species (Callopistes maculatus, one ear; Varanus exanthematicus, seven ears; Gerrhonotus leiocephalus, one ear). The barn owl ears emitted one or two emission frequencies; the lizard ears had one, two, or three emissions. For each peak in the emission spectrum, an amplitude distribution was obtained. By comparing the spectrum and the histogram, it is concluded that the emission signals obeyed partly sinusoidal and partly noise statistics. The latter is presumably caused by random amplitude fluctuations of the emissions. Four out of 7 owl emissions and 7 out of 16 lizard emissions were dominated by sinusoidal statistics. For these emissions, the relative rms amplitude fluctuation ranged from 0.13 to 0.41 for the barn owl, and from 0.04 to 0.29 for the lizards. These emissions must have been generated by an active oscillator in the ear. In one barn owl ear, mutual suppression of two neighboring emissions was observed. This caused one of the two emissions to deviate substantially from sinusoidal statistics. The 11 remaining emissions were dominated by noise statistics, presumably due to large amplitude fluctuations. For these emissions, our data are not conclusive on whether an active oscillator is involved in the emission generation.
Phase delay measurements of distortion product otoacoustic emissions at 2f1−f2 and 2f2−f1 in human ears
Authors: Wable Jocelyne , Collet Lionel , Chéry-Croze Sylviane
Published: October 2005

The present study used distortion product otoacoustic emission (DPOAE) latency as a tool to provide information about the generation sites of 2f1−f2 and 2f2−f1 DPOAEs in humans. The DPOAE 2f1−f2 is supposed to be generated near the f2 site, but little is known about the 2f2−f1 DPOAE processing in humans. The present work sought to test several hypotheses as to the possible generation of 2f1−f2 at the f2 site and of 2f2−f1 at the 2f2−f1 site as well as their backward reflection site, by comparing latencies of the two DPOAEs, under appropriate frequency manipulation. The effect of stimulus level was also studied. The latency values were calculated as the phase-lag related to the frequency shift, using the ILO92 software. Amplitudes were lower and latencies shorter for 2f2−f1 than for 2f1−f2. As expected, 2f1−f2 and 2f2−f1 DPOAE latency decreased with increasing stimulus level and frequency. At 70 dB SPL, latencies of DPOAEs with primaries f1 and f2 or f*1 and f*2, chosen so as to obtain 2f*1−f*2=2f2−f1, were identical, whereas at 55 dB SPL the similarities were less obvious, suggesting two different generation processes. The present study suggests that the comparison of several DPOAE components may produce useful information about their processing within the cochlea.
Psychometric functions for the discrimination of spectral variance
Authors: Lutfi Robert A. , Doherty Karen A. , Oh Eunmi
Published: October 2005

An experiment was conducted to measure the shape of the psychometric function for the discrimination of spectral variance. The stimuli were simultaneous tone complexes comprised of the six octave frequencies from 250 to 8000 Hz. On each presentation the levels of components in dB were drawn independently and at random from one of two normal distributions having identical means but different variances (σN=1 dB, σS=2–10 dB). In the standard two-interval, forced-choice procedure, the listeners’ task was to indicate which complex had the greater variance in component level. The shape of the psychometric function for all five listeners was markedly different from that of an observer limited only by additive internal noise. It was consistent with an observer that gives weight to only one or two components in the complex. However, this result was inconsistent with the weighting functions computed from the trial-by-trial data from these listeners. Both measures can be reconciled if it is assumed that listener weights vary from trial to trial, or that decisions are based on the one tone in the complex having the maximum level.
Lateralization and detection of low-frequency binaural stimuli: Effects of distribution of internal delay
Authors: Stern Richard M. , Shear Glenn D.
Published: October 2005

The position-variable model [R. M. Stern, Jr., and H. S. Colburn, J. Acoust. Soc. Am. 64, 127–140 (1978)], which had been developed to describe binaural phenomena at 500 Hz, is extended to describe and predict binaural lateralization and detection phenomena at frequencies of 250–1200 Hz. The major modification made to the model is the use of a frequency-dependent form of the function that describes the relative number of binaural coincidence detectors in the model as a function of their internal delay. This function is fitted to describe the lateralization of pure tones with a fixed ITD over a range of frequencies, and the ratio of N0Sπ to NπS0 binaural detection thresholds. The extended model describes without further modification the general dependence of the lateral position of pure tones on ITD and frequency, the lateralization of amplitude-modulated tones, and the ‘‘dominant region’’ lateralization phenomenon.