bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of hearing properties and their connection to psychoacoustical parameters
Authors: Johannsen Kai , Prante Holger
Published: July 2002

The sound quality of products is often evaluated in hearing experiments using the semantic differential and a subsequent factorial analysis. In this study the method is applied to determine basic hearing properties. In order to achieve optimal results of the hearing experiment, special interest has been taken in the choice of adjectives and sounds. This selection is based on the results of a previously conducted survey of sound attributes. The selected 25 sounds were recorded using an artificial head and presented binaurally to a jury of 20 adults with normal hearing. A factorial analysis of the ratings on 24 attribute scales produced six factors representing basic perceptive cognitive and emotional hearing dimensions. In a last step connections between these dimensions and psychoacoustical parameters calculated from the sounds were evaluated using an analysis of correlation. Although the results show high correlations between loudness, sharpness, and pitch strength and equivalent attributes, no such connections could be found for the psychoacoustical roughness and fluctuation strength. In order to find better-correlated parameters, other calculation methods for these properties are investigated.
New approach in measuring auditory source width
Authors: Becker Jörg , Sapp Markus , Görges Frederik
Published: July 2002

Depending on the acoustical surrounding sound sources appear to be broadened. This spatial impression can be rated by a quantity called auditory source width. In this paper a new method for determining this auditory source width is presented. The system is based on the reproduction of an artificial head recording of the examined sound field mixed with a pair of virtual acoustic pointers. These pointers can be moved by test persons to fit the left and right border of the sound source whose ASW has to be rated. The acoustical pointers are implemented as digital signal generators followed by real-time HRTF filters, measured in azimuth steps of 2 deg and cross faded between the directions. Investigations on suitable temporal and spectral shapes of the pointer signals have been made to minimize the localization blur of the pointer. The HRTF measurements and the recordings were done with different artificial heads in order to examine their influence on the determined ASW. Furthermore the influence of different sound field reproduction systems—headphone and crosstalk cancellation—are examined.
Volume scattering realizations from ocean sediment sound-speed and density inhomogeneities
Authors: LePage Kevin D. , Schmidt Henrik
Published: July 2002

Synthetic scattered field calculations can serve as a useful tool for evaluating the practicality of estimating bottom scattering properties from in-situ measurements. Here the temporal and angular characteristics of early time reverberation from volume inhomogeneity scatterers in the sub-bottom are investigated using perturbation theory in the framework of a spectral integral approach. In order to model realistic sediments more accurately, the theory treats the scattering from both sound-speed and density fluctuations in the presence of a background sound-speed gradient. To allow the simulation of realistic experimental geometries, the scattered field is propagated to various receivers through a general multilayered waveguide. Results show that there are several distinctive characteristics of the fields scattered by the different mechanisms which depend both on the scattering properties of the bottom and the unperturbed properties of the overall waveguide.
Sediment critical angle estimation via in situ acoustic measurements
Authors: Maguer Alain , Fox Warren L. J. , Bovio Edoardo , Schmidt Henrik
Published: July 2002

The basic physics of sound penetration into ocean sediments is a current area of active research since a good understanding of this phenomenon is essential for designing sonar systems that can detect, localize, classify, and identify buried objects. The sound speed of the sediment is a crucial parameter since the ratio of sound speeds at the water–sediment interface determines the critical angle. Sediment sound speed is typically measured with core samples using high-frequency (100’s of kHz) pulsed travel time measurements. Simulations using Biot theory and taking into account sediment permeability have shown that there may be a significant frequency dependence to sediment sound speed in the range 1–100 kHz. Here, sediment sound speed and critical angle estimation are investigated through the analysis of in situ acoustic measurements. Acoustic energy in the frequency range 2–16 kHz was directed toward a sandy seabottom, and a buried 14-element hydrophone array measured the incoming signals. The critical angle is estimated by analyzing both the variations of the penetration ratios and signal arrival times versus frequency, burial depth, and grazing angle. The influence of bottom roughness and sonar beamwidth on the penetration ratio is also investigated.
Repulsion phenomena in the phase-velocity dispersion curves of circumferential waves on elastic cylindrical shells
Authors: Überall Herbert , Maze Gérard , Léon Fernand , Ripoche Jean
Published: July 2002

The complex eigenfrequencies of an evacuated, fluid-immersed infinite cylindrical shell, when plotted in the complex frequency plane, have been grouped into families corresponding to different types of circumferential waves. The real parts of these eigenfrequencies have been used to obtain dispersion curves versus frequency of the phase velocities of these circumferential waves, which are analogous to those of the Lamb waves on an elastic plate in vacuo labeled A0,A1,... and S0,S1,..., but which contain an additional branch reminiscent of the fluid-borne Scholte–Stoneley wave. This branch forms together with the A0-analog an interacting pair of dispersion curves which will be called A0+ (upper branch) and A0− (lower branch). These exhibit a repulsion phenomenon near the ambient fluid sound speech analogous to that in perturbed, quasi-degenerate atomic levels. This is explained here by perturbation theory, showing that during repulsion the wave character gets exchanged so that at frequencies above the repulsion point A0+ is a flexural and A0− a fluid-borne wave, and vice versa below the repulsion point.
The geometric room model as a surround-sound auralization resource
Authors: Driscoll Michael Thomas , Reuter Eric L. , Campbell Richard H.
Published: July 2002

A large church near the WPI campus was chosen as an experimental site for its splendid acoustics as reported by musicians who perform there. The church was modeled using the CATT-Acoustic software, and the resulting computed acoustic parameters compared favorably with MLSSA measurements taken in the church. A brass choir was recorded in the church using a surround-sound multitrack microphone technique. The brass players were also recorded as individuals with acoustic isolation between the instruments. Each layer’s actual position in the church during the recording session was defined in the model as a CATT source with its associated directivity pattern, and positioned in the church CATT model. Impulse reponses were computed from each source location to a set of CATT receivers which duplicated the surround-sound microphone array. The isolated brass instrument recordings were then convolved with these impulse responses and auralized to a surround-sound mix. The auralized version and the actual recorded version were compared for authenticity by a panel of listeners.
Acoustical modeling and auralization as a design tool for concert hall renovation
Authors: Brooks Bennett
Published: July 2002

A 400-seat university concert hall was modeled using the CATT-Acoustic software system. Good agreement was found between objective measurements and model predictions for the original hall. Also, the subjective quality of the auralized model was judged by music faculty to be an accurate representation of the original hall. These results provided confidence in the model as a design tool for hall renovations. Design decisions were made based on objective parameters, such as early reflection density, and the subjective quality of the sound for a series of model configurations. The final design was largely realized and the renovated hall has been well received by both faculty and community. Sound samples illustrating auralized design options will be presented.
Application of CEN prediction models to German building situations
Authors: Metzen Heinrich A.
Published: July 2002

The calculation models for airborne and impact sound transmission specified in the European standards EN 12354-1 and -2 were applied to a number of common German building situations. Most of the buildings investigated were constructed from heavy elements made of brick or concrete. The measured results for the various situations were taken from qualification tests carried out by German acoustical laboratories or consultants. The calculations were performed by use of the new, commercially available software program bastian, which enables, besides the calculation of airborne and impact sound transmission, the calculation of sound transmission across facades from the outside. Input data not delivered within the bastian database has been estimated. Special interest was focused on the influence of element area and assumed structural reverberation time in situ on the calculated final result.
Vocalization analysis during the castration of pigs
Authors: Marx Gunther , von Borell Eberhardt , Horn Thomas , Thielebein Jens
Published: July 2002

Castration is usually carried out on young male pigs by surgical means to prevent boar taint in older males. The specific structure of vocalizations of piglets may provide some information on the extent of pain experienced by the animal. A total of 96 piglets from 24 litters out of a commercial herd were allotted to four different treatments between the age of d 7 and 19: (a) castration without anesthesia [C], (b) castration with local anesthesia [CA], (c) fixation without anesthesia [F], (d) fixation with local anesthesia [FA]. Vocalizations were recorded with a calibrated microphone (B&K4133) and a DAT recorder (SONY-TCD-D8). Analysis was done with Entropics Signal Processing System (ESPS5.0) software on a workstation (SGI Indy) and provides a multiparametric description of call characteristics. Plasma catecholamines were analyzed from plasma taken immediately after each treatment. Call structure within vocalizations of castrated piglets [C] changed during periods of tearing and cutting of the spermatic cord (call energy: 92.030.41 vs 88.750.31 dB before tearing; p<0.01). CA treatment reduced peak levels (CA: 95.090.65 vs C: 99.350.35 dB; P<0.01). Correlations between call structure and physiological stress parameters indicate that these behavioral characteristics are useful for measuring stress by means of a noninvasive method. Several parameters from numerical analysis of calls were found to be sensitive to stressful treatments during castration.
Do echolocating bats use the acoustic flow field?
Authors: Denzinger Annette , Schnitzler Hans-Ulrich
Published: July 2002

In transfer flight, CF bats continuously emit signals consisting of a long CF and a short terminal FM (tFM) component. So far, the CF component is only discussed in the context of the perception of fluttering insects. However, changes in the relative movement between the bat and the targets it passes create systematic changes in the amplitude and frequency of the echoes. These changes represent an acoustic flow field containing spatial information. To establish whether CF bats evaluate flow-field information, the echolocation and flight behavior of Pteronotus parnellii and Rhinolophus ferrumequinum was studied when flying on known flight paths in the field. In undisturbed flight, signals with a prominent CF and a weak tFM component were emitted (CF mode), well suited for analyzing the available flow-field information. An obstacle introduced directly into the flight path caused an evasive flight maneuver and a distinct change in echolocation behavior indicated mainly by more prominent tFM components allowing a better target localization. New data suggest that bats avoid obstacles positioned aside of the flight path without leaving the CF mode. It is assumed that information encoded in the CF component (possibly flow-field information) is sufficient to guide the bat on known flight paths and around newly appearing lateral targets.
Auditory categories for the perception of echo spectra in bats
Authors: Schmidt Sabine
Published: July 2002

Bats obtain an auditory representation of their environment by sonar. The categories relevant for the perception of echo spectra by Megaderma lyra, a species using multiharmonic sonar calls, were studied in a series of 2-AFC experiments with complex tones. First, the bats classified complex tones on the basis of absolute pitch rather than by their relative pitch. Absolute pitch, combined with a long lasting memory representation of echo spectra, may form the basis of an acoustical library for object identification. Second, evidence was provided for the spontaneous perception of a collective pitch at the fundamental of the complex tones, as well as for the use of a vowellike quality based on the broadband spectral composition of the complex tones. In addition, the bats could be trained to concentrate on the spectral pitch of a single component in complex spectra. Collective pitch, vowel timbre, and spectral pitch perception may all be vital for acoustical orientation in this ground gleaning bat which has to sort out multiple echoes. The collective pitch of the echo allows one to relate each echo to its respective call. The timbre and the spectral pitches of sonar call echoes carry information about object structure. [Work supported by SFB 204.]
The role of selection in marine mammal biosonar: Why pinnipeds don’t echolocate
Authors: Schusterman Ronald J. , Kastak David , Levenson David
Published: July 2002

Pinnipeds inhabit dark and sometimes murky water, as do dolphins; however, they have not evolved sonar. Why? What factors resulted in pinnipeds evolving a different Umwelt from echolocating dolphins, even though at a superficial level, it seems that similar environmental pressures should select for similar Umwelts? Pinnipeds don’t echolocate, because, unlike aquatic dolphins, pinnipeds are truly amphibious. Thus the hearing of seals and sea lions is adapted for sound detection at the low- and mid-range frequencies both in water and air, while dolphins are specialized to hear, localize, and differentiate aspects of high-frequency sounds only in water. Pinnipeds are adapted to combine a variety of sensory cues with spatial memory in order to navigate, forage, detect predators, and communicate under water. Some pinnipeds rely heavily on their vibrissae to forage benthically, while others are specialized in terms of visual sensitivity. Experiments have shown that an elephant seal can become completely dark-adapted in the time it takes (∼5 min) to dive from the bright surface to foraging depths of 500 m. Clearly, the ‘‘apparent’’ selective pressures that would give rise to echolocation in pinnipeds have not been in operation, presumably because pinnipeds perform many reproductive activities on land or ice. [Work suported by ONR.]
Seafloor characterization using a low-frequency multibeam echo sounder: Ambiguities in backscattering strength interpretation
Authors: Lurton Xavier , Guillon Laurent
Published: July 2002

This paper presents the seafloor characterization difficulties and methodological requirements met when dealing with apparent discordances between acoustical data and geological observations. The poor spatial resolution of low-frequency multibeam echo sounders used for deep-water seafloor mapping precludes access to small-scale feature descriptors (spectral, or non-Rayleigh statistics); only average angular backscattering strength (BS) measurements are then available. However, since a given acoustical response may ambiguously represent various geological realities, precise modeling of angular BS accounting for seafloor inner structure and properties is crucial. Oriented medium-scale roughness of the interface may cause level biases, observed as azimuth-dependent BS variations. More noticeably, sound penetration inside the sediment volume may affect strongly the overall response; this is modeled through an equivalent input backscattering strength from buried layers, accounting for propagation phenomena inside sediment stacks. Only confrontation with both accurate sediment coring, in situ geotechnical measurements, and thorough investigations of the geological context may remove these interpretation ambiguities: such a situation is presented and discussed for a difficult experimental case from a deep-sea fan area, where a sandy zone shows lower BS levels than the surrounding clay areas. An interpretation is proposed, based upon the acoustical properties of nonconsolidated sands.
Sediment geoacoustic properties determined from local and spatially integrated measurements of interface waves
Authors: Berger Thomas K. , Hahn Thomas R. , Buckingham Michael J.
Published: July 2002

In Aug./Sept. 1998, as part of a sediment classification exercise at a site near Panama City, Florida and coordinated by NRL, Stennis, a vertical hydrophone array was deployed at mid-water depth to measure the velocity and directionality of interface waves. An airgun, 20-m deep on the seabed and at a range of approximately 1 km, excited head waves, and the received signal was used to invert for the sound speed using two methods: first, by comparing the arrival times of the water wave with those of the interface wave, and second, by considering the critical angle computed from the vertical directionality of the received signal as found from a cross correlation of signals from the hydrophones at known separations. The first method gives an average of the sound speed integrated along the path length, while the second method establishes the sediment properties near the array. The array was allowed to drift, giving measurements along various paths and at different local positions. By comparing the local and averaged properties of the sediment, the heterogeneity was established and the spatial variation determined more completely than could be achieved by either purely averaged or local measurements alone. [Work supported by ONR.]
Seismic depth imaging and remote sensing of rock properties
Authors: Sidorovskaia Natalia A. , Lockard Emmitt S.
Published: July 2002

An inversion of time-domain seismic data to the depth domain is used to enhance the structural signatures of complex geological features. Currently available algorithms for building three-dimensional depth-velocity models are overviewed. It is shown that the accuracy of the numerical model is sensitive to several important factors. First, the quality of the numerical model depends upon the amount of well control incorporated into the inversion algorithm. Second, velocity dispersion in seismic data may be an important parameter for predicting bottom elastic properties, such as porosity, permeability, fluid saturation, etc. The scattering and intrinsic attenuation of the acoustic signal by the Biot and the squirt-flow mechanisms at the macroscopic and microscopic levels for elastic geological structures are reviewed. A new numerical approach based on the scattering from aggregates of fluid-filled elastic objects is also introduced. Currently available numerical models, taking some aspects of elastic scattering into account, and their further development are discussed. The results indicate the first step in remote sensing of complex anisotropic geologic features from broadband seismic data.
Digital signal processing in hearing aids
Authors: Agnew Jeremy
Published: July 2002

For individuals with a hearing impairment, digital signal processing offers the promise of implementing previously unavailable methods of manipulating sound to compensate for hearing loss. However, hearing aids also present a complex technical challenge for the incorporation of DSP technology. Modern hearing aids are powered by zinc-air cells, since this chemistry produces one of the highest energy densities of all battery technologies and results in the most power for the smallest size. However, the use of these cells places severe limitations on the DSP technology that may be incorporated into a hearing aid. The available operating voltage is 1.25 V and, in order to provide an acceptable battery lifetime for the consumer, the available current drain is severely limited. An additional design challenge is that the entire DSP hearing aid must fit into the human ear. This presentation will focus on the complexity of achieving DSP technology in hearing aids within these electronic and mechanical limitations. General discussion will focus on circuitry necessary to achieve DSP in a hearing aid and on the various considerations and limitations that must be taken into account when making design decisions.
A four-microphone noise reduction system for hearing aids
Authors: Kompis Martin , Feuz Peter , Valentini Gregory , Pelizzone Marco
Published: July 2002

A novel four-microphone noise reduction scheme for conventional hearing aids and cochlear implants is investigated. The acoustic field is sampled with a total of four microphones. Two microphones are mounted on either side of the head in behind-the-ear hearing aid housings. Each pair of microphones forms a fixed beamformer, and the outputs of the two devices are post-processed by an adaptive beamforming scheme. The adaptive beamformer is programmed to further enhance target signals emitted in the front of the listener while suppressing noise arriving from other directions. The system has been implemented in real time on a custom-built portable digital signal processing system. The output of the system can be used to drive headphones or the audio input of a number of conventional hearing aids and cochlear implant speech processors. The four-microphone noise reduction system has been evaluated in two different acoustic environments with speech recognition tests conducted on four normal-hearing listeners. Preliminary results indicate an improved directional pattern and significantly enhanced speech recognition in noise, when compared to either a fixed or an adaptive beamformer by itself. In a moderately reverberant room, signal-to-noise advantages of up to 17 dB were observed. [Work supported by the Josephine-Clark Foundation.]
Modeling of acoustics of hearing aid earmold systems
Authors: Szwoch Grzegorz , Kostek Bozena
Published: July 2002

The earmold system of hearing aids guides an amplified and compressed sound into the ear canal. The description of the propagation of acoustical waves in this system is complex because of the fact that the auditory tube is not straight and the eardrum does not form a perfectly flat end. In more advanced hearing aids, the earmolds are acoustically fitted, according to the patient’s needs. However, this is done experimentally during the fitting process. Modeling of earmolds with irregular shapes can be based on the approach widely used in speech acoustic and in digital sound synthesis, namely the physical modeling of acoustical waveguides. The elaborated model uses fragments of tubes of different diameters and lengths. The difference in acoustic impedance at the boundaries of each two fragments is described by the reflection coefficient. The acoustic wave propagation is modeled using a pair of delays. The model enables the finding of a spectral response characteristic of a hearing aid earmold system in the process of its matching to the patients needs. The details of the proposed approach and some results will be presented in the paper. [Work supported by KBN, Poland, Grant No. 8 T 11E 03415.]
Use of immersive sound in a museum exhibition
Authors: Coulter Peter
Published: July 2002

Studies have shown [Schaffer, World Sound Project (1997)] that in our environment, which includes our community, traffic and motorized sounds are growing at a faster rate than nonmotorized human sounds, suggesting that because motorized sound is low-information, high-intensity, it tends to desensitize the populace and results in less social interaction. One role of museums is to preserve a balance of sounds, as a sanctuary from our environment, and explore the consequence of our motorized culture. At the Powerhouse Museum, an exhibition has opened, December 1998, entitled ‘‘Cars and Culture’’ which examines the consequence of cars. In the exhibition there is an immersive sound space that has been created using an ambisonic sound system. This soundscape is discussed. An experiment was devised where the degree of sound immersiveness was varied for a number of visitors and their reactions were measured.
Loudness evaluation of urban soundscapes by a cross-modal matching method
Authors: Susini Patrick , Maffiolo Valerie
Published: July 2002

In a previous study, loudness of a time-varying pure tone was evaluated using a cross-modal matching method. In this procedure, the loudness was matched to an equivalent muscular force. Subjects had to judge the instantaneous and global loudness using a proprioceptive input device with force feedback. Using this technique, subjects could respond easily, rapidly, continuously, and with feedback concerning their evaluation. The present study examines the relation between instantaneous and global loudness of 16 urban soundscapes lasting about 20 s using the same method. First, the procedure is individually calibrated with 1-s soundscapes presented at different sound-pressure levels. The data obtained for each subject fit well with a linear relation on a log–log scale between the sound-pressure level in dB and the associated force in log Newtons. Then, the global judgments are performed under two experimental conditions: one with instantaneous loudness evaluation during stimulus presentation and one without. Good correlation was found between these two judgments. The global judgment and the average over the instantaneous matching contour are nearly identical. In addition, a fluction factor (FI) calculated on the loudness judgment contour reflects the degree of movement produced by the subject as well as the presence of discriminable sources.
Is pleasantness for soundscapes dimensional or categorical?
Authors: Maffiolo Valerie , Castellengo Michele , Dubois Daniele
Published: July 2002

This paper focuses on methodological issues regarding the dimensional or categorical properties of pleasantness for soundscapes. Sixteen sequences of urban soundscapes were recorded and reproduced with their real sound intensity, using techniques previously validated to produce the illusion of a real environment. The sequences were processed using two methods: free categorization and pair comparisons. The categorization method consisted of asking subjects to sort out the sequences according to pleasantness and to verbally qualify their categories. In the pair comparison task, subjects had first to choose, for each pair, which sequence was the most pleasant, and then to rate the pleasantness dissimilarity between the two sequences on a nine-point scale. Categories and ratings were processed through a cluster analysis and interpreted in connection with a psycholinguistic analysis of the verbal comments. Binary choices were transformed onto a dimensional representation of pleasantness. The main results lead to the discussion of the influence of procedures and data representations of the interpretation of pleasantness for soundscapes, and suggest that the dimensional aspect of pleasantness is more an artifact of representation than an intrinsic property of soundscapes. Unpleasant soundscapes seem to be more adequately represented as a specific category of sounds rather than values ranging on a scale.
Practical approach to ANC of fan noise with feedback compensation
Authors: Koníček Petr , Jiříček Ondřej
Published: July 2002

Attenuation of low-frequency noise is a difficult task using passive methods. This paper presents the results of a fan noise reduction in a duct with circular cross section and a small diameter using active noise control. The control algorithm is designed for the optimum least square control in the time domain and contains acoustic feedback compensation. This algorithm was used for the attenuation of noise generated by a small axial fan. The discrete components of noise were totally canceled and the broadband component was reduced. The results of our project will be used for betterment of the working environment.
Noise from airborne air conditioning system
Authors: Zaporozhets Oleksander I. , Tokarev Vadim I.
Published: July 2002

A prediction model for noise produced by an air conditioning system in an aircraft pressurized compartment is described. It is based on analysis of the sound flow energy in air conditioning system channels, including both the generation attenuation effects of the acoustic oscillations within the system. Differences in calculations from those usually used in stationary air conditioning systems for industrial, public, and residential buildings are discussed. The mechanism of noise generation by compressors, cooling turbine, separated flows in regulator, and jet flows from the pipe nozzle are investigated. The calculation results are obtained and carried out for different operational airplane conditions. Optimum tasks for operation conditions of an air conditioning system for noise impact criterion are formulated and solved.
On the determination of dynamic properties of elastic rail fastenings
Authors: Diehl Rolf J. , Hofmann Paul
Published: July 2002

The dynamic properties of the resilient layers of rail-fastening systems play an important role for sound and vibration emission from railway lines. In order to achieve low sound radiation from the rails, a rather stiff fastening for the rail is advisable, whereas for vibration minimization rather soft fixtures would be preferred. The dynamic properties of fastening systems are determined from measurements. In order to have comparable results, a CEN standard is currently being written which is consistent with the method described in ISO 10846 for laboratory measurements of the dynamic stiffness. The method and examples for results will be discussed. For the optimization of the setup for a given situation [track, vehicles, speed(s), operating conditions, surroundings], theoretical models are useful tools. In addition, such models can be used to predict the future impact. Apart from the prediction model itself, the quality of a prediction depends on the reliability of the input data. Results of calculations with the rail/wheel impedance model RIM will be shown to demonstrate the effect of different vertical stiffnesses of the rail fastening and its frequency dependence on the emitted sound and vibration levels.
Directivity of flap side-edge noise as observed with a phased microphone array on landing aircraft
Authors: Michel Ulf , Qiao Weiyang
Published: July 2002

The sound emissions of a large number of aircraft landing at the airport of Frankfurt/Main, Germany, were studied with an 8- by 8-m phased microphone array consisting of 111 irregularly distributed microphones. The data reduction procedure takes account of the motion of the sound sources. The measurement procedure is described and results for the directivity of flap side-edge noise of various aircraft types are reported. Flap side-edge noise is an important airframe noise source on many aircraft and can be clearly identified with the phased array. The variation of this noise source between different aircraft types is considerable, which indicates a substantial noise reduction potential. a)Permanent address: NW Polytechnical Univ., Xian, PROC.
The noise spectrum of isotropic turbulence
Authors: Lilley Geoffrey M.
Published: July 2002

Proudman’s solution for the noise radiated from isotropic turbulence at low Mach numbers and high Reynolds numbers was reviewed by Lilley (1994) following the simulation of Sarkar and Hussaini (1993). It was suggested (Lilley, 1996) that the Lighthill–Proudman theory could be used for the prediction of the radiated acoustic power from turbulent free shear flows in the absence of shock waves. In this approximation the Lighthill ‘‘filter function’’ was used with distributions of the turbulent kinetic energy, the temperature fluctuations, and the turbulent length scale. The results were compared with experimental measurements. But the method (Lilley, 1996) was only concerned with the total acoustic power. Modifications to this theory are required for the estimation of the spectrum and directivity of the radiated sound. The frequency resolution in time-dependent RANS calculation (TRANS) is limited by the grid used. In most, the large scale structure of the turbulence is resolved and consequently the energy containing scales captured. But the high-frequency part of the spectrum is poorly defined. Present work discusses two models for the high-frequency spectral decay and some of the properties of the high-frequency spectrum in turbulent shear layers.
Studies of scattering from differently shaped objects using the TLM technique
Authors: Kristiansen Ulf , Brachet Nicolas
Published: July 2002

The transfer line method (TLM) can be regarded as a discretized version of Huygen’s principle. Wave energy propagates along a system of lines connecting regularly spaced node points. An energy packet reaching a node along a certain line will at the next time step be split up and reradiated into all the lines connected to that node. Wave propagation is therefore regarded as a discretized process in space and time with local updating rules. Special rules are applied for reflecting, absorbing, and partially absorbing surfaces. The method has been used for some time in electromagnetic wave propagation, but not so much in acoustic studies. The present study is a 2-D investigation of the scattering of sound pulses from objects having different shapes: circular, triangular, and rectangular. Performing this in the time domain allows the following of the scattering process in detail.
Scattering from cylindrical structures with various end-cap shapes
Authors: Sarkissian Angie , Dragonette Louis R.
Published: July 2002

The scattered field from a cylindrical structure near the forward direction is computed using the Kirchhoff approximation of scattering from a screen. The effects of varying the shape of the end-caps are examined by carrying out target strength computations for various shapes. The cylindrical region is modeled to be impenetrable while the effects of varying the reflectivity of the end-cap regions are examined. [Work supported by ONR.]
Parameter space of single-bubble sonoluminescence for various liquid temperatures
Authors: Gaitan D. Felipe , Holt R. Glynn
Published: July 2002

In a previous paper by the authors [Phys. Rev. Lett. 77, 3791 (1996)], the region of parameter space (acoustic pressure, ambient bubble radius) in which stable single-bubble sonoluminescence (SBSL) occurs in an air–water system driven at 20.6 kHz was described as a function of the dissolved gas concentration. In this paper, new data (ambient radius, maximum radius, expansion ratio, as well as the emission and extinction thresholds) will be presented for the SBSL parameter space at various liquid temperatures for different gases and liquids. [Work supported by the Office of Naval Research.]
Noise quality of transient sounds: Perception of ‘‘hiss’’ and ‘‘cough’’ in a flue organ pipe
Authors: Rioux Vincent , Västfjäll Daniel , Yokota Munetaka , Kleiner Mendel
Published: July 2002

According to an expert organ builder, the onomatopoeia ‘‘hiss’’ and ‘‘cough’’ must be distinguished from the well-known general term ‘‘chiff’’ in order to describe the characteristic bursts of noise occuring during the transient of many flue organ pipes. These particular sounds can be adjusted and aligned to a certain aesthetic, but this matter has not yet been much discussed by organ experts. This exploratory study mainly relies on a computer-based listening test which has been carried out on two groups of people (musicians and acousticians). The experiment focused on the participants perception of ‘‘hiss’’ and ‘‘cough’’ and also on their ability to extract the ‘‘noisy’’ part from the harmonic components. Even though the sounds were quite similar, the noise/harmonic separation task was successful for a large number of subjects. This supports the hypothesis of a natural perceptual difference between the noise bursts and the concomitant harmonic setup and also the validity of this decomposition. To differentiate and identify ‘‘cough’’ and ‘‘hiss’’ sounds, however, is a much more elaborate task which requires much experience.
A virtual reconstruction of the trumpet
Authors: Tronchin Lamberto , Cocchi Alessandro
Published: July 2002

Virtual reconstructions of musical/instruments have already been analyzed in past years on violins. The ‘‘virtual’’ instruments can be used in subjective listening tests for the evaluation of the sound quality of different instruments, as well as in the restoration of ancient instruments, and for preliminary listening tests on new designed instruments. In this paper, the trumpet is treated as a linear system, characterized by its impulse response. From the IRs measured in different positions in the trumpet, an inverse numeric filter of three trumpets has been obtained, through a new developed technique. From the recording of some original pieces of music, sampled directly inside one of the trumpets, an ‘‘anechoic’’ signal has been obtained by convolution with the inverse filter calculated in the same position. The ‘‘anechoic’’ signal, convolved with the IRs just measured in the other trumpets, produced a signal containing all the acoustic characteristics of the instruments, avoiding all nonacoustic phenomena, and allowed the realization of ‘‘virtual’’ reconstruction of the trumpet. The first results of the listening tests confirm the similarity between the direct acoustic recording and the convolution technique also for the trumpet, as well as already found for the violins.
The wave digital filter brass mouthpiece model
Authors: van Walstijn Maarten , Campbell Murray
Published: July 2002

Wave digital filter (WDF) techniques are applied to develop an efficient discrete-time two-port mouthpiece model that can be used in traveling-wave based modeling of brass instruments. WDF’s were principally developed for simulation of analog networks, and are used here to discretize the classical first-order lumped element mouthpiece model [J. Backus, J. Acoust. Soc. Am. 60, 470–480 (1976)]. The model is segmented into two-port units that are individually mapped to the digital domain using the two-port WDF approach [S. Lawson and A. Mirzai, Wave Digital Filters (Ellis Horwood, London, 1990)]. The realizability of the filter structure is ensured by choosing the port resistances in between the units such that delay-free loops are avoided. The two-port mouthpiece can be directly coupled to models of the lips and leadpipe, although special care must be taken concerning the local characteristic impedance. The WDF mouthpiece model is easy to plug in, its parameters are very intuitive, and it has low computational costs, which makes it particularly suitable for physical modeling with musical sound synthesis purposes. The functioning of the WDF brass mouthpiece model will be further illustrated in a digital wave guide modeling application of a trumpet, wherein all model parameters are derived from measured data.
Limits of utility of dosage-response analysis for predicting the Prevalence of annoyance
Authors: Guski Rainer
Published: July 2002

Dose-response analyses from field studies are essential parts of the information necessary for establishing limits for tolerable noise immissions within the sites (e.g., residential areas with certain immissions) and persons actually studied. But they have their limits when (1) dose-response data are compared between independent studies, (2) annoyance data are extrapolated to other sites, other immission types, levels resp. numbers of noise events, other people, or future times, and (3) the effect of noise abatement programs is predicted. These limitations are presented, using empirical data for illustration purposes. The discussion concentrates (a) on methodological aspects of measuring annoyance, (b) methodological aspects of converting continuous annoyance scales to the percentage of highly annoyed people, and (c) on the contribution of nonacoustic factors to annoyance and to empirical dose-response relationships. It is concluded that dose-response analyses must not be discarded, but their limited utility should be kept in mind.
Measurements of noise annoyance: Decisions on appropriate evaluation procedures in field and laboratory settings
Authors: Schulte-Fortkamp Brigitte
Published: July 2002

The complicated context of noises that are annoying has to be taken into account to measure annoyance adequately. The measurement has to provide insight information improving the understanding of the complex processes causing the annoyance judgments built up in ranking results, e.g., based on categorical judgments. Another problem will be defined by asking which procedure is more or less sufficient to solve the problems of annoyance measurements or should those measurements be carried out in studies combining both field and laboratory. There is the necessity of a consensus that studies on annoyance have to include the context of activities or interference of activities. Two laboratory studies based on a field study evaluating noise from different sources are carried out in different countries. The results point out the context sensitivity of any judgment as well as the measurement procedure guarantee a detailed characterizing of the noises. The subjective judgments correlate with those parameters relevant for the living situation of each subject. For the laboratory experiments the context is defined by associations evoked by the noises presented. Results of both of the studies strongly demonstrate the need for measurements including the context evaluation and an integrative procedure of field and laboratory studies.
Inviscid and viscous computations of supersonic jets
Authors: Lin San-Yih
Published: July 2002

Numerical investigations of unsteady flow fields and associated sound radiations due to supersonic jets are performed numerically. The axisymmetric Euler and Navier–Stokes equations are solved by two numerical methods, modified Osher–Chakravarthy and WENO. The Reynolds numbers based on the jet diameter and the axial velocity are from 700 to 70000. For higher Reynolds number flows, the large-eddy equations are used to accurately capture the large-scale vortical structures. The Smagorinsky model is chosen and the Smagorinsky constant is carefully chosen to avoid excessive damping of large-scale fluctuations. The boundary condition treatments are also studied. Two numerical methods are compared with each other to see the effect of dissipation of each method. Kirchhoff’s integration method is applied to calculate the far-field noise, with the sound source obtained from the calculated time-dependent near field. Details of the flow structures, such as mean flow distributions, shear layer, and the corresponding sound pressure level, are investigated. It is noted that the sound-pressure level obtained by the Euler solver is very high even in the downstream of the jet. Three-dimensional computations are also performed roughly to understand more complicated structures of jet flows.
The confounding influence of collapsing the ear canal on audiological assessment of noise-exposed workers
Authors: Picard Michel , Tremblay Chantale , Dumont Veronique
Published: July 2002

Collapsing of the ear canal resulting from using supra-aural earphones has been studied in a group of 52 noise-exposed workers. Prevalence and audiometric manifestations of collapsing the ear canal were determined based on comparison of pure-tone air-conduction thresholds obtained when insert earphones are substituted for supra-aural ones in the same individuals. Results indicate that as many as 17% of candidates showed in one ear or the other, threshold elevations of 6.6 dB on average at 3 kHz, of 8.1 dB on average at 4 kHz, and of 9 dB on average at 6 kHz as a result of shifting from insert to supra-aural earphones. This finding is of special concern when considering the particular attention paid for the correct positioning of the two types of devices, and the systematic tearing of the tragus in the anterior direction to force the ear canal opening in the positioning of supra-aural earphones. It suggests supra-aural earphones may partially collapse the entrance of the ear canal as a result of the excess pressure applied to the pinna. A model that may help predict the effects of this insidious yet pervasive condition of collapsing ear canals on hearing thresholds of noise-exposed workers will be discussed.
Effects of gas mixture on a thermoacoustic refrigerator driven at high amplitudes
Authors: Poese Matthew E. , Garrett Steven L.
Published: July 2002

Measurements of a thermoacoustic refrigerator driven at pressure ratios up to 6%, with a He/Ar gas mixture have been reported [M. E. Poese and S. L. Garrett, ‘‘Performance measurements of a thermoacoustic refrigerator driven at high amplitudes,’’ Proc. 16th Intl. Congress Acoust. and 135th meeting Acoust. Soc. Am. 2, 809–810 (1998)] and show a 15% lower heat pumping power at 6% pressure ratio compared to the fourfold increase in heat pumping power expected by doubling the pressure ratio from 3%. To further characterize the high-amplitude performance, measurements with other gas mixtures (He/SF6 and He/Xe) were made. These experiments show that while the He/Xe mixture enables the machine to operate with a larger COPR than with a He/Ar mixture, the nonlinear cooling power degradation is more severe: 10% at a 3% pressure ratio and 20% at 6%. Experiments with a He/SF6 mixture show no significant increase in COPR compared to a He/Ar mixture, only a positive shift of the COPR curve with cooling power of about 1.5 in 15 W. [Work supported by Office of Naval Research, NASA, through the Pennsylvania Space Grant Consortium and the Applied Research Lab through the Enrichment and Foundation Program. The authors thank Scott Diehl for generous help with making these measurements.]
Atomic force acoustic microscopy: Acoustical imaging on the nm scale
Authors: Rabe Ute , Hirsekorn Sigrun
Published: July 2002

High-resolution imaging techniques are important tools in materials evaluation and nondestructive testing. Conventional acoustical imaging techniques allow the determination of elastic properties and defect detection with a spatial resolution dependent on the wavelength of the imaging ultrasound. Research work over the last years has shown that this limit can be overcome by combining atomic force microscopy (AFM) with acoustic microscopy. Inducing ultrasonic vibrations in the contact formed by the sample surface with the sensor tip of an AFM opens its high lateral resolution to ultrasonic imaging. Different measurement techniques in which linear and nonlinear effects play a role are possible and have been demonstrated experimentally. An overview of the imaging techniques will be given. Theoretical models which allow the explanation of the image contrast and the derivation of quantitative surface qualities will be discussed.