bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent advances in acoustic sediment classification
Authors: Richardson Michael , Wood Warren , Jans Wolfgang , Fleischer Peter , Briggs Keven , Lavoie Dawn , Lott Dan , Lambert Doug , Lindwall Dennis , Walter Don , Griffin Sean , Smith Eric
Published: July 2002

Most acoustic techniques used to classify seafloor sediments rely on operator experience and require extensive ground-truth data to calibrate system predictions. Recent developments in transducer design, inversion and deconvolution techniques, and sensor motion composition should improve the reliability and accuracy of normal-incidence, seafloor classification techniques. This presentation provides an introduction to papers that describe the application of these techniques to normal-incidence acoustic returns collected from a variety of siliciclastic and carbonate sediments in coastal waters surrounding Florida and the Bahamas. Site locations and descriptions, sediment characteristics based on in situ and laboratory measurements, and a description of the acoustic measurement techniques are given. In addition, 3-D visualization techniques that provide near real-time presentation of results are described. Profiles of sediment acoustic impedance, compressional wave attenuation, seafloor roughness, and volume heterogeneity are directly determined from acoustic returns and physical constraints. Other properties such as sediment type, grain size, porosity, and shear strength are predicted on the basis of empirical relationships relating acoustic impedance and/or attenuation to sediment physical properties. Comparisons of predicted and measured sediment properties are given and the ping-to-ping variability inherent in acoustic returns is discussed. [Work supported by ONR.]
Time-domain numerical solution of the KZK equation for modeling sound beams radiated by rectangular sources
Authors: Averkiou Michalakis A. , Khokhlova Vera A.
Published: July 2002

A time-domain numerical solution of the KZK equation for modeling finite-amplitude sound beams radiated by rectangular sources similar to those used in diagnostic ultrasound is presented. The KZK equation accounts for the effects of diffraction within the parabolic approximation, nonlinearity, and thermoviscous absorption, on the propagation of sound beams. The algorithm is based on that used by Lee and Hamilton [J. Acoust. Soc. Am. 97, 906–917 (1995)] to model circular sources. The diffraction integral has the form of a two-dimensional diffusion equation. The implicit backward finite difference (IBFD) scheme adapted for two dimensions is used in the near field, where the solution tends to be oscillatory. For the remainder of the field, the alternate direction implicit (ADI) method is used for higher accuracy with larger steps than those used in IBFD. The simulation model may be used to predict the FDA regulatory measurements of medical diagnostic scanners.
Modeling of noise generation by turbulence in a larger human blood vessel
Authors: Borisyuk Andriy O.
Published: July 2002

An acoustic model of a larger human blood vessel is developed in order to study noise field in the human chest produced by flow of blood. The model accounts for the basic features of the generation and propagation of noise in the body, and permits consideration of a simple stenotic narrowing in vessel. The low Mach number turbulent wall pressure model of Chase is used to describe random sources in the vessel. The solution obtained relates the mean statistical characteristics of the noise field in the thorax to the parameters of the vessel and the blood flow, and reflects the influence of the body tissue on the sound transmission from the source (wall pressure fluctuations) to a receiver resting on the skin. The numerical analysis of the solution reveals the characteristic signs of the presence of a stenotic narrowing in the vessel. These are increase of the noise levels and production of the new frequency components determinable by the mean flow velocity in and the diameter of the constriction. [Work supported by the Alexander von Humboldt Foundation.]
Ultrasonic examinations of the forward and reflected waves in human arteries
Authors: Powalowski Tadeusz , Trawinski Zbigniew , Hoeks Arnold , Rutten Marcel
Published: July 2002

A new method of noninvasive examinations of the forward and reflected (backward-traveling) pressure waves in human arteries is presented. The study concerned the effect of an artery stenosis on the value of the reflection coefficient modulus and the time delay of the reflected wave relative to the forward wave. The investigations were carried out in the common carotid artery of a healthy person and of a person with 60% stenosis of the internal carotid artery. The instantaneous value of the blood pressure in the common carotid artery was determined from ultrasonic measurement of the instantaneous artery diameter and from the systolic and diastolic blood pressures measured by cuff in the brachial artery. The coefficient of wave reflection was calculated on the basis of noninvasive ultrasonic investigations of the characteristic and input impedance in the common carotid artery. The results of the examinations indicate that a vessel stenosis causes an increase in the value of the reflection coefficient modulus and a decrease in the time delay between the reflected and forward pressure waves at the measurement point just proximal the stenosis. This observation can be of significance for noninvasive diagnosing of atherosclerosis of arterial vessels.
Signal processing algorithms for an open-platform DSP hearing aid
Authors: Edwards Brent W. , Melanson John , Bisgaard Nikolai
Published: July 2002

The development of DSP chips that meet the small-size and low-power constraints of hearing aids has increased the signal processing capabilities of such devices tremendously. Processing schemes that would be difficult, if not impossible, to implement on an analog chip can easily be implemented digitally. These signal processing algorithms for hearing aids can be classified into one of three categories: those intended to restore impaired hearing to normal, those designed to improve speech intelligibility in noisy situations, and those that improve the functionality of the device. The signal processing algorithms for an open-platform, or software-based, DSP hearing aid will be discussed, with an emphasis on features that are unique to this device. These include FFT-based multiband compression, active feedback cancellation, and digitally processed multi-microphone directionality. The perceptual benefits associated with each algorithm will be provided.
Experimental determination of the fluctuating pressure on a rotating fan blade as a source of acoustic noise
Authors: Stremel Michael , Carolus Thomas
Published: July 2002

The fluctuating pressure on the rotating blades is a significant quantity responsible for the noise emitted from axial fans. In order to compute the noise from flow field data, a model is required which describes the fluctuations as a function of flow parameters. The paper presents the fluctuating pressure, measured on the rotating blade of a fan under different operating conditions. The turbulence intensity and the spectral density of the turbulent inflow velocity fluctuations are varied and measured. From CFD calculations quantities, such as boundary layer thickness, shape parameter, etc., of the flow around the blades are deduced and used as parameters. Simultaneously, the noise emitted from the fan is measured and compared to the fluctuating blade pressure.
Short pitch corrugation on straight tracks—Theory and numerical simulation
Authors: Müller Steffen , Knothe Klaus
Published: July 2002

Simulation models (Frederick, Sinclair, Valdivia, Hempelmann) which have been developed during the last 20 years showed the formation of short pitch corrugation to be a frequency constant mechanism, where a track mode about 1000 Hz dominates the corrugation process. Based on this, however, it is difficult to explain the relatively small variation in wavelength with vehicle speed which is observed in practice. In this presentation a sophisticated linear wheel-rail model is introduced which could help in resolving this contradiction. The transient dynamics is described by a feedback loop: Fluctuations in the contact geometry and the creepages cause varying contact forces. This produces fluctuating relative displacements between wheel and rail which in turn change the contact geometry and the creepages again. The simulation of the long-term behavior shows how the rail surface is damaged after a high number of wheel passages. Based on numerical results it is demonstrated that, due to contact mechanical effects, short pitch corrugation is growing within a fixed wavelength band, which could explain why the wavelength varies only a little with vehicle speed. The presented model is therefore a good basis for future research on how short pitch corrugation can be suppressed.
Structure-borne noise reduction in a railway tunnel in Cologne by means of a ballastless mass–spring-system-type Züblin with discrete Sylodyn® bearings and dynamically soft Sylodyn® ballast mats
Authors: Wettschureck Rüdiger G. , Breuer Franz , Tecklenburg Markus , Widmann Horst
Published: July 2002

In the vicinity of Chorweiler (a suburb of Cologne) there is a tunnel in the double track of German Railways between Cologne and Düsseldorf which was built for airborne noise protection reasons. On both sides of this tunnel there are very close housing areas built during the last years. The structure-borne noise of the rail traffic caused a considerable interference with the residents. In 1997 measures to reduce the railway vibrations were installed in both tracks of a 970-m-long tunnel section. In one part of the tunnel, 230 m long, a mass–spring system with a natural frequency of 11 Hz, using discrete bearings, was installed. The rest of the tunnel was equipped with ballast mats tuned to extremely low dynamic stiffening and to main line axle loads (push–pull trains of commuter traffic Rhein/Ruhr) with a specific static stiffness of 0.03 N/mm3 [according to DB-TL 918071, Edition June (1988)]. The efficiency of these reduction measures, that means their insertion loss, was estimated by means of lumped-parameter models, and measurements of the structure-borne noise during train passages were carried out on identical measuring points before and after the structural alterations in the tunnel and in adjacent buildings. The measurement results show a good correspondence with the calculations and completely confirm the high expectations set in the measures.
The ‘‘Owl’’ as a challenge in airframe noise research
Authors: Lilley Geoffrey M.
Published: July 2002

The ‘‘silent’’ flight of the ‘‘owl’’ has captured the attention of the aeronautical community for over 50 years. The silent flight, resulting from changes in the flight feathers of the ‘‘owl’’ from all other birds, notably the leading edge comb, the trailing edge fringe, and the upper wing covering of the velvety down feathers, has been known and carefully documented by biologists, ornithologists, and aeronautical engineers. Many of the noise characteristics of an ‘‘owl’’ have similarities with airframe noise. By training owls to fly with the leading edge comb removed Kroeger et al. (1971) established that the leading edge comb was essential for stable flight at its high lift and low speed. However Kroeger’s measurements showed that the ‘‘owl’’ had a broadband radiated noise spectrum indicating that the flow in the adverse pressure gradient on the rear upper surface was turbulent at the wing trailing edge. The present paper describes the effect of the trailing edge fringe and the down feathers on the noise spectrum generated by the owl and why the owl remains silent to its prey in spite of their excellent hearing above 2 kHz.
Industry perspective on jet noise—Prediction and reduction requirements
Authors: Reed David H. , Bhat T. R. S. , Conley W. T.
Published: July 2002

Spectacular growth of airline passenger traffic, nearly tenfold since 1970, has been fueled by a steady trend toward lower cost airfares made possible by technological achievements in airframe and aircraft engine design. Of all the advancements in aircraft design, none has been more important than that of the high bypass ratio (HBPR) turbofan engine, first introduced in 1969 on the Boeing 747. Since then, HBPR turbomachinery noise technology has kept pace with other engine refinements, allowing newer aircraft to meet increasingly stringent community noise requirements. Even more advanced turbomachinery and nacelle noise technology is now at hand as a result of government/industry efforts in both Europe and the United States. Engines with substantially lower fan noise will be introduced. Jet noise will remain the major obstacle to further noise reduction. Since the majority of new commercial aircraft over the next 20 years will be powered by HBPR engines, research in jet noise must be a major priority. This paper examines the needs for jet noise reduction across the range of commercial aircraft types, and suggests technology development efforts including CFD tools for jet characterization, active flow control, installation effects, and novel suppression devices. This paper also discusses challenges in jet noise technology for supersonic airliners.
Wedge diffraction analyzed by localized response function of the boundary value problem
Authors: Ueda Mitsuhiro
Published: July 2002

A new diffraction principle called virtual discontinuity principle of diffraction, abbreviated by VDPD, which is formulated by considering the wave propagation in a space seen by an observer virtually, has been proposed by this group. The boundary value problem is formulated using VDPD and the Green’s theorem. Then it becomes clear that the response function, which shows mutual dependence of the potential on the surface of the object, is composed of two components. One of them is localized near the edges of the object that can be seen by the observer. The other is not localized, just like the response function used in the BEM formulation of the boundary value problem. The observer in the free space can always see the edge of a wedge. Thus the boundary value problem for the wedge diffraction can be formulated using the localized response function only. As a result of the localization near the edge, sampling points of the potential can be limited near the edge. Thus in spite of the infinite size of the wedge, the numerical procedure to solve the problem is simplified remarkably.
Sound scattering and transmission through cylindrical layer with concentrated defects
Authors: Genis Vladimir I. , Oboznenko Elena I.
Published: July 2002

An experimental method of defect detection in a cylindrical shell is proposed. Defects are the cylindrical hollows (the projections) on the outside or the inside of the shell, filled up, and encircled by water. The defect diameter makes up 1–2 mm (0–0,95) h long, where h—is a shell thickness. The inverse sound scattering field and pass wave field on the shell axis were measured in the sound acoustic beam. Experimental investigations were compared with theoretical investigations by changing the shell wave dimension in the 2–20 range (the 3-D resilience theory). The presence of the shell resonance clears surges and its inside liquid pillar as lengthening of the defect gradually results in their being illegible. The long defects reduce discrimination of the resonance system shell water. The through defect and the Helmholtz resonator are similar. The measurement results of the shells with defects and without were compared, when the shell was radiated by narrow sound beam (the beam width 10–15 times as much as the defect diameter). The theoretical calculation and experimental measurements of the nondefective shell are practically identical. The proposed method serves for defect presence (or absence) definition in pipelines, blood vessels, and others.
Modeling of ultrasonic wave interaction with alumine and silica inclusions in steel
Authors: Mercier Noelle , Chebbo Nazir
Published: July 2002

To progress in the characterization or discrimination of flaws in ultrasonic nondestructive testing, it is essential to have a good knowledge of the interaction of incident ultrasonic waves with these flaws and to model the echographic signals. The flaws considered here are of volumetric type. They have been simulated, in 2-D geometry, by circular cylinder forms. The developed model calculates the stemming time signal of the longitudinal or transverse wave diffused by a cylinder made of a fluid medium, an empty cavity, an elastic, or a rigid solid. The used method is based on the usual modal theory. The time signal is obtained by the Fourier transform of the multiplied monochromatic components, for each frequency, by the spectral response of the transducer. The presented results concern the case of two elastic media which simulate inclusions in steel. The convergence of the modal series, for a quite small flaw, is relatively rapid even for high frequencies. A comparison is presented between experimental and numerical results obtained in retrodiffusion, using a transducer of 10-MHz nominal frequency, for alumine and silica inclusions of about 300 μm. Whereas the beam aspect is not taken into account, the wave curves are similar.
A correlation-measuring system for ultrasonic NDT using maximum length sequences
Authors: Niederdraenk Torsten , Thaden Rainer
Published: July 2002

In the field of nondestructive material testing (NDT), the advantages of a correlation-measuring technique can be used. In particular, the better dynamic range and gain in the signal-to-noise ratio provide a good possibility of investigating strongly scattering or absorbing materials. The ap- plication of maximum length sequences as excitation signals permits the performing of the correlation procedure by using the Fast Hadamard transform (FHT), a very fast correlation algorithm. In nondestructive material testing, a number of special requirements has to be fulfilled. Apart from the driving conditions of the piezoelectric transducers, measurements in NDT often require high measuring frequencies. Based on former developments, a measuring system has been developed that provides a high testing rate; even when using MLS signals of order n=16, a rate of 20 Hz is obtained. A partially parallel calculation structure of the FHT gives a vivid looking presentation of the measuring results.
Higher order effects in finite-amplitude sound fields
Authors: Tjo/tta Sigve
Published: July 2002

Nonlinear effects associated with intense sound fields in fluids are considered theoretically. Special attention is directed to the study of higher-order effects that cannot be described within the standard propagation models of nonlinear acoustics (the KZK and Burgers equations). The analysis is based on the fundamental equations of motion for a homogeneous, thermoviscous fluid, for which thermal equations of state exist. Model equations are derived and used to analyze nonlinear sources for generation of flow and heat, and other changes in the ambient state of the fluid. Fluctuations in the coefficients of viscosity and thermal conductivity caused by the sound field are accounted for. Also considered are nonlinear effects induced in the fluid by surface waves in the transducer. The intensity and absorption of finite-amplitude sound waves are calculated, and related to the sources for generation of higher-order effects.
Second-harmonic component in the focused beam transmitted through a weakly dispersive liquid layer
Authors: Saito Shigemi
Published: July 2002

The characteristic of the nonlinearly generated second-harmonic component in the focused beam which transmits through a layer consisting of weakly dispersive liquid is theoretically and experimentally investigated. In a focused beam, a destructive interference takes place, within the post focal region, between two portions of second-harmonic components which are generated in the pre- and post-focal regions. This is due to the phase delay of the second-harmonic component passing through the focal region relative to the fundamental component. When a weakly dispersive layer is inserted into the focal region, a phase advance occurs for the second-harmonic component passing through the layer due to slightly higher sound-speed for second-harmonic frequency, together with the phase delay due to diffraction. Then the effect of the destructive interference is degraded to result in amplitude increase of the second-harmonic component within the post-focal region. The experiment for a layer of water–oil mixture employed as a dispersive liquid is compared with the nondispersive case and demonstrates the validity of theoretical prediction.
Investigation of nonlinear wave distortion in a focal and post-focal region in water
Authors: Grelowska Grazyna , Kozaczka Eugeniusz , Lypacewicz Grazyna
Published: July 2002

The subject of interest is sources of finite amplitude. Focusing sources belonging to both of the two main differentiated groups of such sources have been examined. The first one consists of sources with additional lens, and the second one of the single-element PZT sources. Previous investigations concerned mainly phenomena occurring close to the source—in a prefocal and a focal region. The phenomena appearing at the longer distances in the post-focal region, where the nonlinear wave distortion is obviously considerably greater than in a pre-focal region, is the main topic of this paper. Experiments are conducted in measurements of spatial pressure distribution in a beam radiated by: (1) a single PZT element focused source with a fundamental frequency of 1.5 MHz, (2) a PZT plane circular source coupled with the plano-concave lens with a frequency of 1.0 MHz. A PVdF hydrophone with diameter of 1 mm was used as a pressure probe. The results of the experiments are compared to the theoretically predicted ones. The sound field was modeled by the KZK equation with the equivalent boundary condition adequate to the actual boundary condition.
Bubble dynamics and SBSL in a variable acceleration environment
Authors: Holt R. Glynn , Roy Ronald A. , Wyatt Sean C.
Published: July 2002

In order to prepare for pending experiments in variable g environments, some of the multiple effects caused by the time-varying acceleration of acoustic resonators used in bubble levitation experiments were considered. The coupled effects of the induced changes in ambient pressure (due to a changing hydrostatic head) and bubble position (due to a change in the buoyant body force) were modeled. Changing the ambient pressure, while holding the acoustic pressure amplitude constant, causes changes in the radial bubble response and diffusive equilibrium requirements. Changing the bubble levitation position causes both the local acoustic pressure amplitude and gradient to change, which will again impact bubble response. If the bubble is required to remain in a stable diffusive equilibrium, both of these effects will force the bubble equilibrium radius to change. Finally, by using an empirical relation for emitted SL intensity versus bubble response, the variation of emitted light intensity as a function of the changing ambient acceleration is obtained. Where possible, these results are compared to experimental data. [Work supported by NASA.]
Mouth tones of flue organ pipes: A control of sound aesthetics
Authors: Castellengo Michele
Published: July 2002

The quality of the steady sound of organ pipes is determined by pipe geometry and blowing pressure. In contrast to this, the attack transient is controlled by both the voicer and to some extent by the player. The initial part of the transient is related to the so-called ‘‘mouth tones,’’ which will be discussed in some detail. On the basis of analyses of the sound production of many organs, the importance of mouth tones during the attack transients of some characteristic stops is shown: Diapason family with initial broadband noises; stopped and chimney pipes with inharmonic ‘‘pings;’’ Viola stop of the Italian organ with long and intense mouth tones persisting during the stationary sound. As frequency content of mouth tones is directly dependent on the air velocity at the flue, any variation of the pallet opening time in the mechanical action or small uncontrolled fluctuations existing in the wind channel produce many variations in the attack transients. Such variations due to the mouth tones give life to the perceived sound quality of the organ, an instrument where sound production is hardly influenced by the musician.
Why are historical brass instruments hard to play in tune?
Authors: Campbell D. Murray
Published: July 2002

Historical cup-mouthpiece instruments, especially those from the Renaissance and Baroque periods, have the reputation of being harder to play in tune than modern brass instruments. This paper considers what is meant by ‘‘playing in tune’’ from both acoustical and musical standpoints, and surveys acoustical features of some early cup-mouthpiece instruments which may have contributed to their reputation for uncertain intonation. Three different classes of instruments are distinguished. The first includes instruments of fixed acoustical length, such as the natural trumpet; the second includes instruments in which the acoustical length may be lengthened by moving a slide or depressing valves, as on the trombone and the valved trumpet; the third includes cup-mouthpiece instruments in which the acoustical length can be decreased by opening fingerholes, such as the cornetto and the serpent. Different considerations affect intonation in each class of instrument. Experimentally derived input impedance curves, frequency spectra of played notes, and threshold pressure measurements using artificial lips are presented and discussed in the context of intonation sensitivity.
Jet and vortex behaviors visualized during the starting transient in organ pipes
Authors: Yoshikawa Shigeru
Published: July 2002

Three types of transient jet behaviors are demonstrated using slow-motion pictures (2 to 30 pictures per second) taken by a high-speed digital video camera (1297 or 1440 pps). (1) The jet issuing from the flue almost always deviates toward the pipe outside and results in a large vortexlike trajectory. When the lower surface of this outwardly curved jet just touches the edge tip, a tiny vortex is likely to be formed beneath the edge. This vortex introduces the first stimulus from the jet to the pipe inside, and in turn significant disturbances are created along the jet. As communicated to the pipe, these disturbances gradually become periodic and well-organized to build a jet wave. This tiny vortex beneath the edge yields a smooth and fast build-up. (2) A much faster build-up is realized when the jet impinges the edge straightforwardly and divides into the two from the jet center. However, this case is rare. (3) A much slower build-up is caused when the blowing pressure is relatively low and a small vortex tends to stand between the flue and the edge. This stagnant vortex may yield a ‘‘two-crest’’ jet wave prior to the formation of an ordinal ‘‘one-crest’’ jet wave.
Numerical simulation of jet noise: Fundamental issues, progress and outlook
Authors: Lele Sanjiva K.
Published: July 2002

High-speed jets remain noisy and loud today. Can high-fidelity numerical simulations provide a new and unique vantage point in future studies of jet-noise and its suppression? What physical and numerical challenges must be overcome in such computational approaches? What features of jet turbulence must be explicitly computed? What is the impact of ‘‘sub-grid’’ scale models, and what precautions must be exercised to avoid ‘‘spurious’’ sources? These fundamental issues will be discussed in the first part of the talk. Recent progress in simulations of high-speed jets, including large eddy simulation (LES), will be presented. The need to examine carefully the interplay between the effects of numerical approximation and physical models being used, will be stressed. The role of reduced-complexity model problems related to jet noise will be discussed and results on sound generation from shock-vortex interaction in a jet mixing layer will be highlighted. Open issues in jet simulations and jet noise modeling will be stressed throughout. This talk includes collaborative work with colleagues Jon Freund, Bendiks-Jan Boersma, Ted Manning, Tim Colonius, and Parviz Moin. [Financial support was (in part) provided by AFOSR under Grant No. F49620-98-1-0355 and NASA under Grant No. NAG 2-1213.]
Use of linearized Euler equations for subsonic flow noise prediction
Authors: Lafon Philippe
Published: July 2002

The introduction of efficient numerical techniques like Tam’s DRP scheme allows one to develop aeroacoustic modeling based on Euler equation solvers and applied on realistic configurations. It is already clear that the system of Euler equations is the most complete one in order to compute acoustic propagation in fluids, but the way to calculate noise generation with the same equations needs to be established. So, it is necessary to introduce in the propagation calculation some information coming from a previous or a simultaneous flow calculation. One approach is to try to define source terms for the Euler equations as it was set up for Lighthill’s or Lilley’s equation. Others approaches can rely on the coupling of the two equation systems by domain decomposition or by introducing disturbances linked to flow calculation. The SNGR model belongs to the first category. A source term is defined by analogy with Lilley’s equation. A stochastic space time turbulent field is used in order to avoid expensive LES or DNS flow computations. This approach is mainly applied to the calculation of noise radiated by internal flows where the methods based on the classical acoustic analogy do not work easily.
Hearing thresholds of pupils and apprentices between the ages of 15–19 years
Authors: Körpert Karl
Published: July 2002

Since the early 1990s, several authors have reported on the decreasing hearing ability of young people. The audiograms of the 15–19-year-old men and women show a pronounced dip at 4 and 6 kHz, which was not observable a decade before. This fact was observed also in the hearing conservation programs applied to nonoccupationally noise-exposed apprentices in Austria. A commonly suggested reason for that is increased noise exposure in leisure time. To find out if there are differences between apprentices and pupils of the same age, respectively, if information campaigns run during the last years led to an improvement in the hearing status, audiometric investigations were performed in factories and schools in 1992 and 1997. The results of these measurements and relation to leisure time behavior, investigated by questioners, will be reported.
Thermoacoustic resonator and its sound source: Model of the coupling and experiments
Authors: Lotton Pierrick , Bailliet Helene , Bruneau Michel , Gusev Vitali
Published: July 2002

Current thermoacoustic devices typically consist of a sound source loaded by both a ‘‘rear’’ cavity and the ‘‘front’’ thermoacoustic resonator. The main element placed in the resonator is a stack supporting a temperature gradient, sandwiched between heat exchangers. In thermoacoustic refrigerators, heat transfer along the stack depends on the acoustic power flux available. In the framework of a previous model [Bailliet et al., ‘‘Coupling between loudspeakers and thermoacoustic cavities,’’ submitted to Acta Acustica], this acoustic power can be determined knowing the electrical voltage applied to the source, an electrodynamic loudspeaker, the goal being to optimize the coupling between the loudspeaker and the thermoacoustic resonator. However, in this model, the temperature gradient along the stack is set to zero. The main purpose of this paper is to include in this model the temperature gradient along the stack. The expression of the input acoustic impedance of the thermoacoustic resonator is modified using an approximated analytical solution of the linear equation for the acoustic pressure inside the stack. The efficiency of the coupled system is expressed, yielding the highest acoustic power flux available in the stack (controlled in this study by LDA measurements) for a given electrical voltage applied to the loudspeaker.
A learning program in psychoacoustics with interactive computer-based listening experiments
Authors: Kremer Martina , Krahe Detlef
Published: July 2002

The processing of dynamic sound files in psychoacoustic listening experiments and learning software will be demonstrated by the multimedial learning software called ‘‘Audite.’’ In the field of psychoacoustics, the computer can be used as a universal medium to combine high-quality listening experiments with the presentation of multimedia learning software. They can be generated off-line, depending on the parameter input of the customer. Problems occur if the software should be presented online in the Internet. In this case, only low-quality sound files can be generated interactively. Further, the possibilities of the multimedia representation are reduced so the realization of reasonable didactic structures becomes more difficult, too. By the development of new program structures, the implementation of dynamic and high-quality sound files generated at the run time is realized. In addition, the insertion of improved script languages allows the representation of system-independent multimedia information and the realization of improved interactivity by the customer.
The effect of crook profile on the perceived playing properties of the bassoon
Authors: Sharp David B. , Wright Howard A. K. , Ring William
Published: July 2002

Previous measurements [Sharp et al., Proc. Intl. Symp. on Musical Acoustics, 209–214 (1998)] have shown a difference between the profiles of bassoon crooks manufactured in the first half of this century and those manufactured in the second half. Although all the measured crooks have approximately the same initial and final radii, earlier crooks (manufactured by Heckel) typically have a wider bore in the midsection than crooks made more recently (both by Heckel and other manufacturers). Bassoonists have claimed that older Heckel crooks have more desirable playing characteristics than more modern crooks. Psychoacoustical tests were performed to investigate this claim, and to determine whether listeners can distinguish between sounds produced using different crooks. In the tests, players were recorded performing individual notes, scales, and a musical passage on a reference bassoon using a variety of crooks. The crooks were concealed from the players to prevent visual identification. The performers were then questioned about the playing qualities of the crooks. Pairs of sounds produced using different crooks were presented over headphones and listeners were asked to make judgments on the timbres of the sounds. Results from the tests are discussed with reference to the crook profile measurements.
An interdisciplinary study on railway and road traffic noise: Behavioral results
Authors: Griefahn Barbara , Deppe Carola , Moog Rudolf , Mehnert Peter , Moehler Ulrich , Schuemer-Kohrs Anke , Schuemer Rudolf
Published: July 2002

Mainly, laboratory studies revealed traffic noise as a dominant environmental cause of sleep disturbances. They are less suitable to reflect situational or individual factors. In many countries noise pollution is limited at the legally defined night hours. Hence, the aim was to estimate the influence of timing of sleep determined by working hours, preferences of sleeping times related to individual factors like eveningness, age, gender, etc. During 10 nights, the sleep of 377 apparently healthy people was indicated by actimetry and sleep logs and related to the individual outdoor noise levels emitted either by railway or by road traffic. As expected, indicators of sleep were found to depend on timing of sleep and on individual variables as age, morning–eveningness, etc., whereas none of the various parameters of noise revealed significant relations to sleep disorders. However, source-related outdoor noise did not meet the real situation indoors. The impact of railway/road traffic noise on sleep at home cannot be judged yet, but has to be answered, because sleeping times were not covered in 50% of the cases by the legally defined night. Moreover, work flexibility is expected to increase as well as traffic density during the night.
Sound propagation prediction with emphasis on planning needs
Authors: Ringheim Matias
Published: July 2002

Significant research efforts are directed toward understanding various aspects of outdoor sound propagation. Some of the results can be used when creating noise prediction methods for planning purposes. From a planning point of view, it is necessary to use prediction algorithms and noise descriptors which are relevant in terms of community disturbance and annoyance. Our knowledge of community noise response is largely based on social surveys, and the results are mainly related to fairly simple noise descriptors. There is often a striking contrast between the available knowledge relating to human response, and the detailed nature of sound propagation studies. There is a clear need for prediction improvements, but not necessarily in directions that seem to dominate present research. For planning purposes, it is appropriate to use the noise impact foundation to identify potential prediction improvements and related research topics. The consequences of this point of view will be discussed.
Sound power determination by using sound intensity scanning procedure—Adequate sound-field indicators and criteria limiting the measurement uncertainty
Authors: Hübner Gerhard , Gao-Sollinger Yumei , Wittstock Volker
Published: July 2002

The uncertainty of sound-source sound power determined by an intensity scanning method depends on the one hand on several measurement parameters such as scanning speed, integration time, density of scanning pattern paths, measurement equipment quality, and on the other hand, on the sound field quality having met under the actual in situ measurement conditions. In order to guarantee certain limits for the measurement uncertainties, it is necessary to adjust the measurement parameters to the actual specific conditions for the sound field under test. In the past (see ISO 9614-1) this adjustment was carried out with success by first determining certain indicators describing the actual sound field situation numerically and using the indicators together with relevant criteria in order to check the initially chosen measurement parameters in respect to the given uncertainty limits. At present, an international standard for a relevant scanning precision method (ISO 9614-3) is in preparation. Thereby, adequate indicators and criteria are in discussion worldwide. By an extensive measurement program carried out under well-defined laboratory conditions, and on machines in situ completed by theoretical investigations, certain proposals result that are relevant for the new standard, which will be presented in the paper.
Determination of the airborne sound power radiated by structure-borne sound sources of arbitrary shape—First step of extension of the direct finite-element method to three-dimensional sources
Authors: Hübner Gerhard , Gerlach André
Published: July 2002

The direct-finite-element method (DFEM) is an algorithm for calculation and measurement of airborne sound power radiated by structure-borne sources. Using a structure-borne source parameter directly means redundant intermediate sound field information such as sound pressure and sound intensity are not necessary. Previous investigation showed that for plane structure-borne sound sources, the DFEM can be derived from the Rayleigh description of sound radiation exactly. This paper deals with the extension of the DFEM for three-dimensional structure-borne sound sources. For these sound sources the DFEM algorithm as already used for plane structure-borne sound sources must be supplemented by a net of imaginary counter sources in order to meet the boundary condition of the arbitrarily shaped vibrating body. This supplement is described and discussed using some examples. Finally, measurement results are presented which are in good conformity with the theoretical results of the modified DFEM.
Numerical computation of underwater sound scattering from a complex elastic object
Authors: Homm Anton M.
Published: July 2002

There are numerous analytical approaches for the calculation of sound scattering from cylinderlike structures. However, limitations exist in the complexity of objects, which can be handed that way. In this case numerical methods are necessary to compute the acoustical response of the model. The investigated structure consists of two cylinders of different radii connected by a conical section. The ends are covered by hemispherical caps. An axisymmetric finite-element code (SARA2d) has been used to calculate the response of the target, due to an incident plane wave. Semi-infinite elements are implemented at the boundary of the acoustic fluid to take care of the Sommerfeld radiation condition. In the covered frequency range, which comprised Helmholtz numbers up to ka∼13, specular and elastic properties of the target contribute to the scattered signal. The calculations were performed during a one year research stay at the Naval Undersea Warfare Center (NUWC) in Newport, Rhode Island, USA. Additionally an attempt has been made to compare parts of the results with boundary element methods (SYSNOISE) and coupled FEM/BEM (ANSYS/SYSNOISE). For the coupled calculations only three-dimensional methods have been available, hence those results are restricted to relatively low Helmholtz numbers.
Leaky wave scattering contributions for tilted thick cylindrical shells in water above the coincidence frequency: Ray theory and computational models
Authors: Blonigen Florian J. , Marston Philip L.
Published: July 2002

Scattering measurements [Morse, Marston, and Kaduchak, J. Acoust. Soc. Am. 103, 785–795 (1998)] and sonar images [Kaduchak, Wassmuth, and Loeffler, J. Acoust. Soc. Am. 100, 64–71 (1996)] demonstrate that above the coincidence frequency, the responses of tilted cylindrical shells associated with leaky antisymmetric Lamb waves can give major contributions to the scattering of sound. Thin-shell dynamics is not applicable for the modeling of the shell’s response and an approximate ray formulation has been developed for situations where exact solutions are unavailable. Relevant contributions include meridional [P. L. Marston, J. Acoust. Soc. Am. 102, 358–369 (1997)] as well as helical [P. L. Marston, J. Acoust. Soc. Am. 102, 1628–1638 (1997)] leaky rays. The present research emphasizes computational tests for situations where helical antisymmetric Lamb wave contributions are important. These include situations where contributions from the broad meridional ray enhancement interfere with helical ray contributions. The results are helpful for interpreting features of the scattering. [Work supported by the Office of Naval Research.]
Computational methods and experimental measurements of scattered ultrasonics transient fields
Authors: Hassina Khelladi , Hakim Djelouah
Published: July 2002

The aim of this study is to find the transient acoustic field scattered by a target with a known dimension and geometry. The target is a rigid reflector immersed in an isotropic, homogeneous, and lossless fluid. For that purpose, the presented model takes into account not only the impulse response of the insonified medium, but also that of all the elements which constitute the electroacoustic line. The main elements of the latter are a transmitter-receiver system and an ultrasonic probe modeled by its electroacoustic and acoustoelectric impulse responses. In the hypothesis of a linear, invariant, and causal measurement line, the detected pressure is expressed in the form of a time convolution between the impulse response of all the elements which compose the electroacoustic line and the impulse response of the medium. This last depends on the geometry of transducer, target, their relative position, and the propagation medium. A signal processing method of the experimental data is developed in order to evaluate the global impulse response system. The results of this process will then be used to obtain, by simulation, the effective pressure signal. Some experimental results are presented to show the good agreement with the theoretical model proposed.
Toepler, Mach, and Wood: The visualization of sound
Authors: Beyer Robert T.
Published: July 2002

The 19th Century saw great strides in making sound visible. A major pioneer was August Toepler (1836–1912). Toepler studied the so-called singing flame. To make periodic fluctuations visible, he interposed a rotating disc with slits between the flame and the viewing telescope. In so doing, he developed the idea of the stroboscope, which ultimately became a common device. In a second experiment, Toepler focused the image of a spark source; he then covered the image with an opaque screen. If the rays of light passed through a region with a differing index of refraction, the rays would be bent and thus miss the opaque covering. Toepler called this method schlieren beobachtung, or striae observation. The American, R. W. Wood, popularized this second technique. Examples will be shown. Even before Wood, Ernst Mach (1836–1916) applied Toepler’s method to the study of shock waves. Examples will also be shown here.
Characterization of elastic materials by resonance acoustic spectroscopy
Authors: Honarvar F. , Sinclair A. N. , Fan Y.
Published: July 2002

Application of resonance acoustic spectroscopy (RAS) for characterization of various properties of elastic materials is discussed in this paper. Resonances are indicators of the elastic properties of the material such as density and elastic constants. They can also signal any perturbation in layer thickness and interfacial contact of a multilayered rod. Using a novel technique, called material characterization by RAS (MCRAS), the elastic constants of isotropic materials are measured to within 0.3%. MCRAS is compared with other techniques for determining elastic constants, and is observed to be simple, quick, and applicable in cases where other techniques fail to work. Characterization of elastic properties of nonisotropic materials is also considered, and experimental results on continuous-fiber metal matrix composite wires are presented. It is also demonstrated how RAS can be used for measurement of cladding thickness and detection of cladding delamination in coated rods. Experimental results are also presented on using RAS for gauging the extent of nonisotropy and approximate grain size of transversely isotropic materials.
Double-strand cellular DNA damage by lithotripter generated shock waves
Authors: Kochański A. , Mejnartowicz J. , Latos-Bieleńska A. , Etienne J. , Filipczyński L.
Published: July 2002

During the last years the biological effects of exposure to SWL have been intensively investigated. In contrast to the other studies the litho- tripsy effects on cellular DNA have been rather poorly analyzed so far. In the present study the influence of the therapeutic level energy (18- and 20-kV) shock waves on the cellular DNA was analyzed. These levels of energy correspond to 16 and 30 MPa, respectively. The DNA was analyzed by the classical agarose electrophoresis approach. In contrast to the previously published data, the present results of the DNA analysis strongly suggest the double-strand DNA damage by shock waves generated by the lithotripter. This kind of double-strand DNA damage precludes the cell survival. Therefore, the used methods may be a useful approach in monitoring the biological processes in which the biological tissue is exposed to shock waves generated by a lithotripter.