bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of subjective properties of a sound field in a concert hall with tenth-scale model
Authors: Ishida Koji , Sugino Kiyoshi , Tachibana Hideki
Published: July 2002

This paper discusses a scale model experiment for room acoustic design of the Yokohama Minatomirai Concert Hall which was opened in June 1998. Priority was given to subjective evaluation in the acoustical design process. To this end a measure to improve S/N ratio of the impulse response and filtering procedure for cancellation of the influence of sound source were investigated. Binaural impulse responses measured with different boundary conditions of the hall were convolved with dry sources, and simulated sounds were compared subjectively. The examination of the auralization reflected on interior design. Comparison of subjective and objective properties with full scale and scale model has been carried out in order to verify auralization using scale model experiment. Good agreement on both evaluations was obtained.
A new client-server system for auralization
Authors: Moldrzyk Christoph , Metzler Bernard
Published: July 2002

A system for parallel calculation of sound fields was developed. The system will provide for remote, concurrent access via Internet. A remote user will be offered the opportunity to upload three-dimensional room geometries onto the server. The room impulse response will be retransmitted after its calculation. It will locally be convoluted with appropriate dry sounds. Parallel computing—depending on the number of available processing engines—will allow speeding up the calculation several times compared with existing solutions. The service offered can be used at any location depending on Internet availability. Additionally, the server system comprises a data archive of acoustic measurements and architectural information (geometries, materials, etc). Integrating it into Internet services will establish a unique opportunity for the user—while planning rooms at the desk or any location—to get online information about the physical behavior of his/her intended design. Many users may use the system simultaneously with different requirement profiles. The proposed approach also allows for real-time convolution on the server if the user–server connectivity offers appropriate bandwith. The Internet Resource Reservation Protocol RSVP will be employed to reserve sufficient bandwith. Assuming adequate network behavior, real-time performance could be guaranteed.
A simulation package for room acoustics with an open interface
Authors: Bartsch Guido
Published: July 2002

The solution of complex acoustic problems of the low-frequency sound field presupposes the numeric implementation of the wave equation. Especially for the calculation of sound fields in a finite volume (interior problem), the method of the finite elements (FEM) can be applied. The software market gives the acoustic engineer many different commercial simulation packages, which have no or only a limited user interface for user extensions. This was the reason to create the simulation module called WaveSolve3D. Due to its high portable structure WaveSolve3D can be used on all current and future computer generations, and thereby permits the running of the application on the hardware with the best computing power. In the context of this paper some simulation results computed by WaveSolve3D will be presented. Verification can be achieved by comparison with analytical results in simple enclosures or with measurement results for more complex rooms. The work is part of a project which intends to extend the frequency range in room acoustical computer simulation.
Verification of using SEA to model differing laboratory conditions
Authors: Smith Sean , Pompoli Roberto
Published: July 2002

In the Inter-comparison of European Laboratory Measurements of Airborne Sound Insulation of Walls under the EC Measurement and Testing Programme 1990–1994 a significant difference, of up to 12 dB, was found in the reproducibility results for the participating 21 laboratories. This difference was associated only with specimen 1, the double leaf lightweight plasterboard wall. This paper presents possible reasons for the large reproducibility values for this wall using experimental evidence and theoretical models, statistical energy analysis (SEA). While the calculation of the sound reduction index (R) does take into account the different test wall areas and reverberation times of the respective laboratories involved, some factors which may prove significant to the measured R values are not. This paper discusses a variety of factors which may affect the resultant R values. It is suggested that the principle factor which may effect the results of this test program for the double wall is the material used for the border of the test opening in the various laboratories, which connects both leaves of the double wall. The SEA can be used to model approximately the various laboratory conditions. When comparing the measured and SEA predicted reproducibility results there is good agreement.
Noise transmission through a finite plate: Physical approach
Authors: Masyukov Valery A.
Published: July 2002

The problem of forced sound transmission through a thin elastic plate of finite size, placed in an infinite rigid baffle, is considered on a basis of the following simple approximation of radiation coefficient as a function of angle of incidence: the secant (as for an infinite plate)—below and at some angle called diffractional and a constant (as for a small plate)—at higher angles. The constant depends only on Helmholtz number and is easily obtained in a 2-D approximation. Simple analytical expressions are deduced for the transmission coefficient allowing not only for the finite plate size but also for a lack of near-grazing incident waves in the noise angular spectrum. These expressions are in excellent agreement with complicated 3-D computations fulfilled earlier. A clear physical explanation is given for the well-known underestimation of transmission loss (TL) of real panels by the infinite-plate diffuse-field theory both below and at coincidence. At coincidence, the lack of near-grazing waves and averaging over 1/3 octave band are shown to be responsible for the discrepancy. The obtained formulas can be used for easy calculation of TL for real plates in a full audio range.
Mechanisms of auditory distance perception in passerine birds
Authors: Naguib Marc
Published: July 2002

Use of auditory cues to assess the distance of signaling conspecifics (called ranging) is a difficult, albeit important, perceptual task in animals and humans. Cues are provided by the changes in a signal (degradation) that accumulate with increasing propagation distance. This contribution focuses on mechanisms of ranging and on its accuracy in two passerine birds species. Playback of tape-recorded songs presented to territorial Carolina wrens (Thryothorus ludovicianus) in the field showed that subjects used reverberation, the relative intensities of high frequencies, and the amplitude of conspecific song as auditory distance cues. Use of several cues could increase the accuracy of ranging by pooling information derived in different ways. Thus further experiments addressed specifically the accuracy of ranging in chaffinches (Fringilla coelebs). Playbacks with digitally degraded songs (in a virtual forest) suggest that distance perception involves uncertainties. The results will be discussed with regard to the perceptual processing of acoustic signals and in light of problems caused by the variation of acoustic properties of the environment. [Work supported by Sigma-Xi Grants-in-Aid of Research, the Chapman Memorial Fund of the American Museum of Natural History, and the University of North Carolina at Chapel Hill.]
Otoacoustic emissions and their neuronal correlates in the Mongolian gerbil
Authors: Faulstich Michael , Koessl Manfred
Published: July 2002

Though distortion product otoacoustic emissions (DPOAE) are widely used in hearing research, some fundamental properties of their generation and transmission are still unclear. To investigate the properties of the generation and propagation of DPOAE, as well as the degree of their neuronal encoding in the auditory system, DPOAE in the ear canal and the corresponding neuronal representation of cochlear distortions in the AVCN of the gerbil have been measured simultaneously. Additionally, the group delay for the 2f1-f2 DPOAE was measured for frequencies between 1 and 60 kHz. It was found that for frequencies above 2 kHz, forward and reverse sound transmission via the middle ear are comparable and that DPOAE are encoded practically unattenuated in the AVCN. For frequencies below 2 kHz, a loss of DPOAE amplitude of up to 40 dB compared to the intracochlear level could be observed, most likely stemming from high-pass filtering by the middle ear during reemission. For frequencies above 2 kHz, the group delay decreased with increasing frequency, but additionally, an atypical decrease of the group delay for frequencies below 2 kHz was found. This may indicate a change of the character of nonlinear cochlear mechanics for low frequencies represented in the cochlear apex.
A theoretical and experimental examination of seabed discrimination using the first and second backscatter from an echo sounder
Authors: Heald Gary J. , Pace Nicholas G. , Dyer Cathy M.
Published: July 2002

At normal incidence it is possible to detect a second echo from the seabed in addition to the first echo that is traditionally used by echo sounders. It can be shown that the second backscatter contains information about the seabed that is not contained in the first backscatter. The second echo requires treatment as a bistatic, on axis, geometry in order to understand the mechanisms that provide new information. The effective range of the source is three times the water depth, whereas the receiver is at the water surface for the case where the transducer is at the water surface. The bistatic geometry means that the receiver may be in the near field of the scattering from the seabed. This would mean that the second echo is sensitive to changes in the reflection coefficient of the sediment. Modeling the water surface roughness is achieved by expanding the beamwidth of the source to a level that is representative of the spreading at such an interface. Data from controlled tank experiments over a range of sediment types and water surface conditions are presented. Time-series data from an ocean experiment have been analyzed and show good agreement with ground truth data.
3D compounding of B-scan ultrasound images
Authors: Krücker Jochen F. , Meyer Charles R. , Tuthill Theresa A. , LeCarpentier Gerald L. , Fowlkes J. Brian , Carson Paul L.
Published: July 2002

Ultrasound imaging compounded from different look directions can significantly decrease speckle noise and increase structural contrast. In addition, current limits on the field of view from small aperture scanheads can be overcome by combining two or more sets of partially overlapping 3D scan volumes into one super-volume by spatially coregistering the overlapping portions. The purpose of this study was to demonstrate both of these compound imaging enhancements. A 1.5-D linear array was used to obtain overlapping ultrasound volumes in phantoms and test subjects, reconstructed from at least 60 parallel B-scan planes for each volume. In the cases where independent look directions were required, either the transducer was tilted or the scan direction was changed. In all cases, the overlapping volumes were coregistered using an automated procedure based on a mutual information (MI) metric. The algorithm accounts for different look directions and/or tissue motion by geometrically transforming one volume set such that the MI of its overlap with the other is maximized, which leads to good structural overlap. The accuracy and stability of the MI algorithm demonstrate the feasibility of both compounding methods, offering increased lesion contrast and 3D fields of view larger than those from any currently available ultrasound imaging systems.
Normalized noise spectra of aircraft take-off and landing operations
Authors: Santiago J. Salvador , Pons Jose
Published: July 2002

At Madrid-Barajas Airport, a new runway will enter into service in the year 1999, located to the NW of the two existing ones. This fact implies a new configuration of flight paths, both for take-off and landing operations, and a new definition of the areas adjacent to the airport as regards the noise impact on the population. An ad-hoc regulation states that the dwellings within the area covered by the isophones of Leq day=65 dB and Leq night=55 dB, for the future situation in the year 2010, have to be supplemented by the airport operator with an acoustic insulation to achieve an internal noise level of Leq day=35 dB and Leq night=30 dB. The noise spectra that will be used for measuring the actual insulation of the buildings have been determined along the isophones Leq=80 dB to Leq=55 dB, in steps of 5 dB, for take-off and landing operations, by means of in situ tape recordings of 938 aircraft operations, recorded simultaneously in six measuring stations. Out of 5245 valid recordings, 2749 with enough signal-to-noise ratio were analyzed in 1/3 octave bands, and the results presented as spectra normalized to 0 dB.
Noise problems, savage approaches. From ‘‘just forget it,’’ to physical violence
Authors: Elizondo-Garza Fernando J.
Published: July 2002

Different approaches and/or philosophies that can be used to face a noise problem are described and commented on. Both the classical noise control procedures and the savage approaches that go from simply ‘‘forget it,’’ to physical violence, are considered.
Assessment of low-frequency noise in dwellings. New Polish recommendations
Authors: Mirowska Marianna
Published: July 2002

The paper presents the new Polish recommendations for evaluation of low-frequency noise penetrating into dwellings from appliances installed inside or outside of building. Based on measurement data of annoyance noise, epidemiological investigations of the influence of noise on the health of exposed inhabitants, laboratory tests of thresholds of narrow- and broadband noise perception, review of the present literature, the new assessment criteria was proposed. In order to assess the noise spectra measured in dwellings, the A10 characteristics as the rating curve have been accepted. Its L levels for one-third-octave bands are determined by relation: LA10=10 kA. The low-frequency noise occurs as annoying when the sound pressure levels of noise exceeds the levels of A10 curve and exceeds the background noise by more than: 10 dB for tone noise and 6 dB for broadband noise.
Aeroacoustic response of a six-bladed axial fan to installation effects
Authors: Lalanne Jean-Guillaume , Boden Hans , Abom Mats
Published: July 2002

First, the effects of the duct on the aeroacoustic response of an axial fan have been studied experimentally and theoretically. The loading effect was modeled by a 1D model in the plane-wave frequency domain. This model was validated experimentally by changing duct lengths and fan positions. Second, an experimental characterization of the inflow turbulence has been done. Single degree-of-freedom statistical parameters have been measured as autocorrelation and temporal autospectrum for the axial turbulence components in order to estimate the integral scale and turbulence intensity. In parallel (the fan being located between an anechoic room and a reverberant room), sound pressure and sound-power measurements have been carried out. Different grids and supercritical screens have been designed to change the inflow conditions. The next task is to determine the spectral pattern in both the temporal frequency and tangential wave number domains and correlate it to acoustic response. Only the tonal part of the spectrum is considered. [Work supported by EEC.]
Time domain simulation of railway noise
Authors: Nordborg Anders
Published: July 2002

The most difficult problem concerned with railway noise generation is the process occurring in the contact region during rolling. The following computation efficient time domain model determines the vertical rail deflection by use of Green’s function of a periodically supported beam. Nonlinear Hertzian contact mechanics are used, less realistic, however, than a discretized contact region allowing for rough surfaces. The wheel is as yet a rigid mass. More advanced contact and wheel models can readily be included later. Calculation results include the following observations. The contact force peaks sharply precisely above the support points, followed by a short loss of rail–wheel contact, also for smooth rails. Vibrations of the rail pinned–pinned mode are impossible to eliminate by removing surface roughnesses, because the excitation is above all caused by forward wheel velocity together with discrete supports. The response amplitude increases with forward velocity. Optimum pad stiffness depends on corrugation amplitude. These new findings should be considered when trying to noise optimize track constructions.
Short pitch corrugation on straight tracks—Practical experiences
Authors: Klimpel Thomas , Knothe Klaus
Published: July 2002

One possibility to reduce rolling noise is to reduce roughness excitation. The basis of the paper is measurements of profile irregularities on a test section of the track between Baarn and Amersfoort in the networks of Nederlandse Spoorwegen (NS). In one of two segments, periodic wear pattern (short pitch corrugation) appears with wavelength from 3.5 to 4 cm, whereas the second one is uncorrugated. The line is used only in one direction and mainly by passenger cars with medium speed. Starting from the measured track data, systematic calculations with the program of Müller, which is presented in a separate paper, have been undertaken. The aim is to estimate the roughness growth and to find hints about how the growth can be stopped or at least reduced. In Müller’s paper it is explained in detail that roughness growth is restricted to a wavelength range between 2 and 10 cm. Numerical results will be presented in order to clarify how different track components influence the RGG process. The model only takes into account wear as a long-term mechanism. It shall be discussed how the long-term behavior is influenced by plastic deformation, hardness variations, or different values of micro-roughness.
Scattering by cylindrical shells: The Scholte–Stoneley wave nature
Authors: Veksler Naum , Izbicki Jean-Louis , Conoir Jean-Marc
Published: July 2002

A systematic study of the A wave revolving around circular cylindrical elastic shells immersed in water is performed. The resonance frequencies and halfwidths have been computed for a wide range of the b/a ratio (b is the inner radius and a the outer one). The A-wave evolution is studied from the case of the quasisolid cylinder to the case of the very thin shell (b/a equal to 0.99). The resonances are computed from the complex frequency plane; it is then possible to get the dispersion curves of the A wave. The phase velocities dispersion curves, plotted against the adimensional variable ktd (kt is the shear wave number and d the thickness of the shell), practically coincide in the low-frequency range. The resonance halfwidths are small in this frequency range. The A wave is a bending type wave. At higher frequencies, the A wave becomes analogous to a diffracted Franz wave.
Depth profiling of residual stress in steel by laser ultrasonics
Authors: Gao Weimin , Elton Silvio , Kruger X. , Glorieux Christ , Van de Rostyne Kris , Lauriks Walter , Thoen Jan , Charlier Jacques
Published: July 2002

Depth profiling of residual stress in steel is of great interest in many practical applications. Conventional techniques are either destructive (x-ray diffraction and hole drilling) or with obvious restriction (Barkhausen noise). This paper presents a noncontact and nondestructive laser ultrasonics method for determining the depth profile of the residual stress layer in steel samples. It is known that surface acoustic waves penetrate into solids to a depth proportional to the wavelength. They are expected to be dispersive in the presence of gradients in physical properties such as residual stress. Based on the dispersion theory, the depth dependence of an effective velocity v(z), which is related to the stress profile S(z), can be fitted from the frequency dependence of the phase velocity v(w). Due to the advantage of wide bandwidth, laser-generated and -detected surface acoustic waves (SAW) offer a promising nondestructive stress depth profiling method. The profiles obtained by SAW are compared with the stress data obtained by other techniques. a)Also at Service de Métallurgie Physique, Université Libre de Bruxelles, Belgique.
The decay of pulses with complex structure according to Burgers’ equation
Authors: Gurbatov Sergey N. , Pasmanik Galina , Enflo Bengt O.
Published: July 2002

Nonlinear plane acoustic waves propagating through a fluid are studied using Burgers’ equation in the two cases: small viscosity and viscosity tending to zero. The evolution of initial pulses with monochromatic and noise carrier is considered. The initial pulses are characterized by two length scales. The length scale for substantial changes of the modulation function is much greater than the corresponding scale of the carrier. Some simple pulses with only one length scale are also studied, since their properties are important for the studies of pulses with two scales. With increasing time, the initial pulses are deformed and shocks appear. The shocks then merge, and finally a finite pulse ends up with an N wave and a periodic signal with a sawtooth wave. The decrease of the energy of the wave with time is investigated for pulses with both monochromatic and noise carrier and for vanishing and finite but small viscosity. How the characteristics of the final waves depend on the characteristics of the initial waves is also investigated. Both numerical and analytical methods are used.
On ambiguity in the description of sources and the choice of the acoustic variable
Authors: Musafir Ricardo E.
Published: July 2002

In a homogeneous medium at rest, a classical problem of source ambiguity is expressed by the fact that one cannot differentiate between the fields of a volume displacement point monopole and of a volume acceleration isotropic point quadrupole. In more complex situations, a similar identity concerning the fields of more elaborate combination of point sources can be shown to exist. This reflects the fact that, since two types of energy are involved in the propagation, one cannot tell, from the wave field alone, of which type was the action responsible for originating the wave, there existing, ideally, always a way of representing a ‘‘mass’’ source by a combination of ‘‘momentum’’ sources and vice versa. It is shown, however, that, depending on the choice of the acoustic variable—and thus on the operations needed in order to combine the continuity and momentum equations into a single equation, this elegant picture may not be clearly displayed in the wave equation. The particular case of the use of the stagnation enthalpy as dependent variable is examined as an example, the analysis being used to discuss its adequacy as a variable for aerodynamic noise problems.
Numerical calculations of woodwind impedances without adequate experimental data: Personal experiences
Authors: Strong William J.
Published: July 2002

Some numerical calculations of impedances of an oboe showed relatively good qualitative agreement with experimental data [G. R. Plitnik and W. J. Strong, J. Acoust. Soc. Am. 65, 816–825 (1979)]. With the apparent success of the numerical method, input impedances were calculated for a number of ‘‘woodwind-like’’ structures. On the basis of these calculations a paper was prepared and submitted for publication. Some six months after its submission it was returned with numerous comments regarding errors in its content. A recurring comment from the reviewer was ‘‘the digital computer where used alone has contributed directly to most of the difficulties of this paper.’’ Previous to receiving the reviewer’s comments the author was using the same numerical method to calculate resonance frequencies of a flute. Difficulty was being experienced in getting reasonable agreement with experimental results. However, after incorporating empirical data into the representation of toneholes rather good results were obtained with the numerical method [W. J. Strong, N. H. Fletcher, and R. K. Silk]. A brief history of these experiences will be presented along with pertinent details from the papers and the reviewer’s comments.
Flow and upstream impedance in wind instruments
Authors: Hoekje P. L.
Published: July 2002

The salient features of the behavior of a wind instrument can be explained by the now-common model of an air column resonator coupled with a flow controller; this paper presents clarifications in that model. The reed flow controller is driven by a pressure difference p and generates a flow u; its nonlinearity spreads energy across the spectrum, converting energy from the dc energy source of the player’s breath. The instrument air column is characterized by its input impedance Zd=pd/ud, where the subscript d denotes the downstream side of the reed. Upstream is the player’s airway, characterized by Zu=pu/uu and controlled by the player. The sum (Zd+Zu) provides feedback to the reed, and when Zu is comparable to Zd, the playing qualities of the instrument appear to change. The flow waveform can be estimated from ud=pd/Zd, which can then be compared to predictions from dynamical models of the reed motion. To the extent that the reed is incompressible, then ud=−uu, and Zu can be estimated from the measurements (Zdpu/pd). Evidence will also be presented of the nonlinearity of the air column response at loud playing levels.
Foot resonance in an organ pipe
Authors: Segoufin Claire , Fabre Benoit , Rioux Vincent , Yokota Munetaka , Kob Malte , Kleiner Mendel
Published: July 2002

Pressure measurements in the foot of an organ pipe under playing conditions show acoustical pressure fluctuations induced by the acoustic field in the pipe. Fluctuations of the pressure difference between the foot and the mouth of the instrument results in jet velocity fluctuations that can absorb or produce acoustic energy depending on relative phase with the acoustic pressure in the mouth of the pipe. In most flue organ stops, pipe dimensions indicate that the first pipe resonance and the Helmholtz foot resonance should lie close to each other at least for one pipe in the stop. The present work was triggered by the question of knowing why this does not seem to bother organ builders. Measurements of Helmholtz foot resonances as a function of the driving pressure carried on a pipe with adjustable foot volume are presented. Measurements indicate a damping of the resonance due to the flow through the mouth that can be accounted for by an elementary model of the flow through the mouth. Analysis indicates that, unlike recorder playing, the jet velocity guarantees an efficient damping.
Analysis of time-frequency structure of woodwinds’ sounds, with usage of discrete wavelet transform
Authors: Klapper Magdalena
Published: July 2002

The purpose of this paper is a presentation of analysis results of sounds of woodwinds. The aim of the research was to observe the characteristic properties of the time-frequency structure of particular instruments’ sounds, considering the sound register and dynamics. Special attention was paid to the range of tone color registers and possible loudness of sound within them. A trial was undertaken to define the reasons for the division of the instruments’ scale in several tone color registers. The mathematical methods used to perform the time-frequency analysis of the instruments’ sounds were: mainly multilevel discrete wavelet transform, and also traditional methods: fast Fourier transform and short-time Fourier transform. Discrete wavelet transforms seems to be an especially useful tool for observation of changes of sound parameters. The methods mentioned above vary in distribution of time-frequency analysis. Each of them delivers fragmentary information of the time-frequency structure of the sound; however, they are complementary to one another. Within the framework of the paper a comparison of the analysis results of instrument sounds of quite different properties of time-scale structure are presented.
Experimental investigations of wall influences on woodwind instrument sound
Authors: Nederveen Cornelis J. , Dalmont Jean-Pierre
Published: July 2002

Influences of wall vibrations and thermal/viscous dissipation at the walls on loudness and sound quality of some woodwind instruments (clarinets, recorders, organ flue pipes) were investigated experimentally. Instruments with various wall thicknesses and wall porosities were studied. Wall vibrations were not found to influence the air oscillations except for a very thin-walled cylindrical organ flue pipe. For this pipe, level increases of 3 dB and perceptible sound quality changes were observed when the upper part of the pipe was clamped. From input impedance measurements of instruments geometrically identical, but varying in wall porosity, it was found that the quality factor of the resonances could vary by a factor of 2. The sound level produced by blowing these instruments appeared (at a certain blowing pressure) to be proportional to the real part of the input impedance. The pressure level at which a recorder overblows appeared to increase with the input impedance. Besides wall damping, variations in the bore, which determine the exact positioning of eigenfrequencies, were also found to affect loudness and sound spectrum.
Reed instruments, from small to large periodic oscillations
Authors: Gilbert Jöel , Dalmont Jean-Pierre , Kergomard Jean
Published: July 2002

Reed instruments are physical systems which can be considered as self-sustained oscillators. The ‘‘normal operation’’ of the instrument corresponds to the establishment of a permanent periodic regime. On the one hand, the behavior of the small periodic oscillations in the fixed point (threshold) vicinity is well known: the bifurcation’s nature and the oscillation’s characteristics depend on both the excitator and the resonator. On the other hand, a theory has been developed for lossless resonators coupled with the excitator: compared to experimental results, this theory is relevant for large amplitude oscillations. The matching between the analytical solutions of the two theories is not instantaneous. The matching is studied using the harmonic balance technique with the continuation method coming from known analytical results near the threshold. The bifurcation graphs are constructed for different resonators. The particular resonator with two harmonic resonances is discussed in detail. The role of the octave regime is unexpected: the octave is matched to some of the fundamental regimes. Some resonators (cylinder, lattice of cylinders, cone) are arranged on an artificial mouth designed for single-reed woodwinds. Measurements of periodic regimes are compared to the theoretical results. A movie will be shown.
Jet noise simulations using the nonlinear disturbance equations
Authors: Morris Philip J.
Published: July 2002

Large eddy simulations (LES) of turbulent high Reynolds number flows require significant computational resources if scales in the inertial subrange are to be resolved. However, solutions of the Reynolds-averaged Navier–Stokes (RANS), with an appropriate turbulence model, can provide an efficient and accurate solution for the time-averaged flow. The present formulation recasts the Navier–Stokes equations into equations for the nonlinear perturbations about the RANS approximation to the mean flow. The instantaneous fluctuations are decomposed into a time-averaged component, a resolved large-scale perturbation about this mean, and an unresolved small-scale perturbation. A subgrid scale (SGS) model is used to describe the unresolved scales. The resulting equations are solved on parallel computers using a domain decompositon strategy. Calculations are performed for both circular and rectangular jets. The grid used for the numerical simulations is described. The turbulent fluctuations in the jet, including the time average of the nonlinear perturbations, are presented. Direct simulations of the near and far fields of the jets are given. The jet far field is computed by both direct simulations and with a Ffowcs Williams and Hawkings method. Comparisons are made with available experimental data. [Work supported by NASA Langley Research Center.]
Numerical simulation of jet screech tones
Authors: Tam Christopher K. W.
Published: July 2002

Screech tones are discrete frequency sounds radiated from imperfectly expanded supersonic jets. The tones are generated by a feedback loop driven by the large-scale instability waves of the jet flow. In the plume of an imperfectly expanded jet is a quasiperiodic shock cell structure. Screech tones are produced by the interaction of the instability waves and the shock cells as the former passes through the latter. Although the screech phenomenon has been studied over many years, many of its features are still not understood. Presently, there are accurate tone frequency prediction formulas. However, there is no known way to predict tone intensity. In this study, the screech phenomenon is investigated through numerical simulation using CAA methods. The simulation reproduces all the characteristic features of jet screech, including the staging phenomenon. The computed screech frequencies and intensities are found to compare well with experimental measurements. Numerical results on the effects of jet temperature also compare well with experiments. The favorable agreements indicate that numerical simulation is a valuable tool for investigating the jet screech phenomenon. [Work supported by NASA Lewis Research Center Grant NAG 3–2102.]
Analysis of sound generated by free shear flows using direct numerical simulations
Authors: Avital Eldad J. , Luo Kai H. , Sandham Neil D.
Published: July 2002

The sound produced by large-scale structures in free shear flows is investigated using direct numerical simulations (DNS). Both temporal and spatial DNS approaches are investigated, with special attention given to the former due to its lower computational cost. It is shown that the temporal approach can be used to investigate Mach-wave generation but not the general sound emitted by large-scale subsonic sources. Consequently, temporal DNS data of supersonic mixing layers undergoing transition to turbulence are analyzed. Two dominant Mach waves are found, each of which is identified with vortical features in the flow. The spatial DNS approach is then investigated to study the effect of the computational box size on the sound calculation. A large-scale model is used to show that the low-subsonic case is more restrictive in that sense than the supersonic one. The first case is further investigated by calculating the basic radiation emitted by axisymmetric jets, using the compact Lighthill and Mohring–Kambe formulations. Boundary corrections are developed and tested to reduce the box size effect and to improve the agreement between the two formulations. Finally, the effect of the retarded-time variation along the jet is discussed.
Distortion product otoacoustic emissions—Valuable method for hearing conservation programs?
Authors: Matéfi Laszlo
Published: July 2002

Pure tone audiometry as a screening method for hearing conservation programs has been well established for years. However, it takes a certain time, requires a good cooperation of the patient, and indicates only the damage already caused. Otoacoustic emissions and especially the distortion products have recently been discussed as an alternate method for screening examinations. In the context of this prevention program, some hundred subjects have been examined as usually pure tone audiometry and in addition by measuring the distortion product otoacoustic emissions. The evaluation has been done in the context with the hearing loss measured by pure tone audiometry, with the history of noise exposure, and with the reliability of the distortion product otoacoustic emissions. The present results show that there is no reliable association between neither distortion products and hearing loss measured by pure tone audiometry nor between the distortion products and the noise exposure history. The only association found was between important hearing loss measured by pure tone audiometry and absence of distortion products. So, it can be said that distortion product otoacoustic emissions are not a reliable method to be used as screening measurement in hearing conservation programs.
Hydrodynamic analog of a thermoacoustic device
Authors: Keolian Robert M.
Published: July 2002

An apparatus that oscillates one medium past another is used to demonstrate the principles of a thermoacoustic device. By analogy, heat pumping is represented by the flow of water uphill. Temperature is represented by the water height. The two oscillating media are sheets of Lexan Thermoclear plastic (GE Plastics). Water fills the hollows within the plastic sheet and participates in the so-called bucket brigade, which transports water in this demonstration, or heat in an actual thermoacoustic device. [Work supported by the ONR.]
WWW-based acoustics education—Considerations and implementation
Authors: Rahkila Martti A. , Karjalainen Matti A.
Published: July 2002

The World Wide Web, WWW, is without a doubt one of the most interesting environments for computer-based education, acoustics being one of the areas of teaching. Technically, the WWW is a moderately simple system and it provides platform independence, easy operation for users, and easy use of multimedia information for content providers. But when it comes to WWW-based education, things just aren’t so simple anymore. At the Helsinki University of Technology Acoustics Laboratory, computer-based acoustics education has been a research interest for several years now. This paper considers various aspects of WWW-based acoustics education from the point of view of content design and user interaction, not forgetting usability issues or learning evaluation questions either. The goal is to explore the possibilities of the WWW technology and find the most suitable ways of providing self-study, interactive education material of acoustics and audio signal processing. Moreover, the paper discusses implementation details of interactivity, user control, and evaluation. Acoustics and sound-related topics such as on-line processing and network audio problematics have been included. An example technical solution, a ‘‘User Agent’’-style architecture, is presented along with a tutorial level sample application.
Education of applied acoustics for students of automotive engineering
Authors: Foken Wolfgang
Published: July 2002

Every year 120 students of automotive engineering are enrolled at the University of Applied Sciences in Zwickau (Germany). It is extremely necessary to give them an overview knowledge in the field of applied acoustics. The aim of this paper is to present some methodical aspects of these lessons. Practical tutorials are an essential part of these lessons. Exemplary, the tutorial ‘‘Indoor noise of the passenger compartment’’ is selected. For example, the task is to scan the indoor sound field with a 2-D microphone array and to compare the obtained modes with results from FEM/BEM calculations. The students become familiar with practical measuring methods, with the spectral analysis equipment, and, last but not least, with the application of numerical methods in acoustics. For students of automotive engineering having somehow an ‘‘emotional’’ relationship to the object ‘‘car’’ it is always useful to provide a lot of practical appli- cations. The theoretical fundamentals should be trained; however, the lessons must not be overloaded with theoretical treatises. This way it is possible to make the students sensitive to problems of acoustics.
Diagnosis and therapy for brasses. Methods of measurement, evaluation, and improvement of the acoustical quality of brass wind instruments
Authors: Widholm Gregor J.
Published: July 2002

The operation of brass wind instruments and the relationship between their mechanical parameters and acoustical properties are more or less well understood. Problems may arise if one attempts to compare, e.g., measured intonation or response with the judgment of professional players. It can be seen that brass instruments have a measurable objective intonation quality and may have two or more different subjective qualities because of the fact that instrument and player are parts of a closed control loop. Methods are described to obtain objective quality parameters, taking into account the player’s contribution. An example is the dependency of intonation values on the played dynamic level. In the second part of the paper, recently developed software tools for researchers and instrument makers are presented. While in the past most emphasis was put on diagnosis only, today’s increased processing power allows one to focus on therapy tools based on optimization algorithms. Computer optimization requires a description of the instrument shape which is automatically modified in order to improve the instrument quality, as indicated in a user-defined target function. Obtaining the shape of an instrument is difficult unless bore reconstruction from measured input impedance can be performed. Results of current research are presented.
An interdisciplinary study on railway and road traffic noise: Acoustical results
Authors: Moehler Ulrich , Liepert Manfred , Schuemer Rudolf , Griefahn Barbara
Published: July 2002

Former studies have discovered differences in annoyance reactions determined by questionnaire between railway and road traffic noise. The night time disturbance reactions caused by road traffic noise showed greater scores at the same noise levels than those caused by railway noise. Therefore an interdisciplinary study examining questioned annoyance reactions (day and night time reactions) and also measuring sleep disturbance was conducted. In eight areas—four areas with predominant road traffic noise and four areas with predominant railway noise—acoustical, psychological, and physiological data were gathered. Acoustical indices for both sources were calculated for all subjects using German standards. For subjects taking part in the physiological examination, acoustical measurements indoor and outdoor the bedroom have beeen taken in 10 nights per area. The physiological measurements of sleep disturbance have been taken by actimetry. The acoustical measurements show typical differences between railway and road traffic noise. Several acoustical indices have been calculated from the measured data and corelated to both psychological and physiological data. There is high correlation between the acoustical and psychological variables for both sources whereas the correlation between acoustical and physiological data is very low (see also Schreckenberg et al. and Griefahn et al.).
A review of current strategies and criteria for low-frequency noise control from combustion turbines
Authors: Putnam Robert A. , Hetzel Roland , van de Logt Johannes
Published: July 2002

The environmental noise impact on neighboring communities from power generation installations containing large industrial combustion turbines is often dependent upon the level of low-frequency sound emission. Compliance with commonly specified C-weighted far-field criteria can be a particular challenge. An improved knowledge of the low-frequency sound emissions from the combustion turbine exhaust is required, as well as a design approach which accounts for the possible need for future corrective measures. Such design strategies will be defined and described together with the results of actual case histories of successful installations.
Noise emission measurements in situ—A comparison between different methods
Authors: Jonasson Hans G.
Published: July 2002

Within the frame of a European project within the research program Standards, Measurements and Testing, different methods for the determination of emission sound pressure levels and sound power levels have been tested. The different methods have been ISO/DIS 3747, ISO 9614-2, the ISO 11200 series, that is ISO 11201, 11202 and 11204, and a new method, ISO ‘‘11205,’’ using the sound intensity level to approximate the emission sound pressure level. Comparison measurements have been made on several different machines in situ using eight different measurement teams on each machine/test site combination. The results indicate that ISO 11202 tends to overestimate the emission sound pressure level in relation to ISO 11201, that ISO 11204-4 has a limited field of application, that ‘‘11205’’ tends to underestimate the emission sound pressure level, in particular for large machines with noise emitting parts far from each other, that ISO/DIS 3747 works very well, and that ISO 9614-2 tends to underestimate the sound power level in relation to ISO 3741. The results are discussed and possible improvements to the different standards are proposed.
Remarks about the local environmental correction for determination of the emission sound-pressure level
Authors: Sehrndt Gustav A. , Biehn Karlheinz
Published: July 2002

One of the standards for the determination of the emission sound-pressure level (ESPL) uses a local environmental correction K3 which takes into account both the average sound-pressure level (VSPL) on a measuring surface and an average environmental indicator K2 [ISO 11204, ANSI S12.43]. K2 may be determined either by estimation of the absorption area or by measurements with a reference sound source (RSS); these include also determination of the VSPL. K3 is most important for sources with distinct directivity. To investigate bias and errors of K3 for these sources, a few model machines and source-room configurations have been used. On illuminated microphone positions, results show standard deviations of repeatability for the ESPL of the same order of magnitude as these for the VSPL. In the shadow of sound, bias and errors will sum up and are amplified by the characteristics of the K3 calculation method. [Work supported by BauA.]
Timbral effect of parameter interchange between musical instrument types
Authors: Beauchamp James W.
Published: July 2002

One method of studying the perceptual importances of physical parameters is to generate stimuli involving parameter interchange between instrument types. A new method of doing this models each instrument in terms of excitation and filter, derived from spectral analysis data, and includes independent temporal controls for fundamental frequency, spectral centroid, and amplitude. When temporal parameters are interchanged between instrument models, hybrid sounds result where it is possible to recognize perceptual aspects of both original instruments. When a parameter is inserted into a new environment, its value toward suggesting a particular instrument type may be enhanced. This paper explores conditions under which interchanged parameters may evoke particular instrument responses as opposed to simply merging with the new environment. Such salient parameters may assist in efforts to classify automatically instrument types.
Memory for melodies, poetry, faces, and other complicated things
Authors: Dowling W. Jay
Published: July 2002

For over 100 years it has been a well-known ‘‘fact’’ of research on memory that after something is memorized, it is gradually forgotten over time. This is largely true of the relatively impoverished and meaningless materials that memory researchers have typically relied upon. As early as 1913, Ballard showed that poetry can be recalled better and better following memorization (‘‘hypermnesia’’), and recent work by Erdelyi and others supports those results. Hypermnesia in recognition, however, has proved elusive. The present experiments demonstrate hypermnesia in recognition memory for unfamiliar folktunes. The complexity and meaningfulness of stimuli such as melodies, poetry, and perhaps faces evoke memory processes that lead to improvement rather than decay over the early span of time following acquisition.