bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of objective assessment methods for tonal noise from wind farms
Authors: Ostendorf Holger , Weber Reinhard
Published: July 2002

The perceived impact of wind farm noise depends not only on the overall level of noise emitted, but also on the character of the noise. In particular, the presence of tonal components increases the subjective annoyance. Procedures for the detection of tonal components in the environmental noise and for the assessment of the annoyance due to these components have been proposed in national standards and legislation, e.g., German norm DIN 45681 (draft), Joint Nordic Method. To validate tonality calculation procedures, noises from a representative sample of nine wind turbines of German wind farm sites were recorded by means of a dummy head at the emission measuring point nearby the turbines. Together with a set of five synthesized pink noises with tonal components of different strengths, ten selected wind turbine noises were randomly presented at equal loudness over headphones. Sixteen subjects had to assess categorically the tonality of each noise, which occurred six times in two sessions. The resulting subjective answers showing high inter- and intraindividual agreement could serve as an excellent validation basis for eight selected tonality calculation procedures. It will be shown that the prominence ratio-based methods are the best in modeling subjective tonality assessments.
Psychat—A program for psychoacoustical tests
Authors: Scholz Matthias , Rioux Vincent , Västfjäll Daniel , Kleiner Mendel
Published: July 2002

Sound quality investigations require flexible sound and graphic handling, available on usual personal computers. Psychat is a program designed to fulfill requirements of flexible sound quality testing. The core idea of this program is to offer a fully modular system manipulating objects like audio-players, functions that present visual stimuli or other I/O devices and adaptive descriptor scales. With the help of a graphical editor test leaders can create their own test configuration. Several tests can be linked to a whole project and can be saved as templates and used in other projects. Standard sound quality experiments and more complex tests can be created without programming skills. The principle of modularity allows growing functionality, keeping compatibility, and adapting the system to the users needs. The program collects raw data, includes some basic statistical methods, and offers possibilities to export data in a number of formats.
Sensory dissonance of two-tone complexes
Authors: Rakowski Andrzej , Miskiewicz Andrzej
Published: July 2002

Sensory dissonance, a basically unpleasant auditory sensation related to amplitude or frequency modulation of sound, is an element of a broader concept of musical dissonance. The present study was carried out to determine the magnitude of sensory dissonance produced by beats in two-tone complexes. The method of absolute magnitude estimation was employed for scaling. The measurements were obtained for tone frequencies ranging from 32 to 4000 Hz and beat frequencies ranging from 2 to 2000 Hz. The results show that at beat frequencies higher than 20 Hz, sensory dissonance is equivalent to roughness. The beat frequency at which the maximum of roughness and of sensory dissonance is observed increases with the frequency of the low tone in a complex, ranging from 20 for a 32-Hz tone to about 100 for a 4000-Hz tone. At beat frequencies lower than 20 Hz, sensory dissonance is produced by audible fluctuations of loudness. The effect of loudness fluctuations on sensory dissonance is most pronounced in the range of lowest audible frequencies.
Influence of condition variation on learning in auditory backward masking
Authors: Wright Beverly A. , Fitzgerald Matthew B. , Johnston Paul A. , Reid Miriam D.
Published: July 2002

The influence of condition variation on learning rate in an auditory backward-masking task was assessed by measuring pure-tone detection thresholds in 24 different trial blocks in five groups of eight normal-hearing adults assigned to different conditions midway in the testing sequence. Thresholds for a tonal signal (10 ms, 1000 Hz) presented immediately before a noise masker (300 ms, 200–1800 Hz, 40 dB SPL spectrum level) were evaluated in blocks 1–9 and 19–24. The decrease in threshold observed between the means of blocks 1–3 and blocks 19–24 depended upon the condition tested in blocks 10–18. Mean threshold decreased by nearly 20 dB for listeners who detected a backward-masked tone presented in a temporal gap between two maskers, by around 15 dB for listeners who detected a backward-masked tone at a higher frequency or a forward-masked tone, and by around 12 dB for listeners who did the standard backward-masking task or who rested for 20 min. This information may be useful for the development of interventions for elderly persons and children with language impairment who have been observed to have excessive auditory backward masking. [Work supported by NIDCD and the McDonnell-Pew Program in Cognitive Neuroscience.]
Wavelets transform in oscillation and optimal feedback control of smart cantilever thin-walled beams
Authors: Poterasu Victor Florin , Librescu Liviu L.
Published: July 2002

Based on the recent results obtained by Na and Librescu concerning the dynamic response characteristics of thin-walled cantilever beams made by smart materials subjected to transient loadings, this paper proposes to use the technique of wavelets transforms. As smart materials, the piezoelectric elements in the optimal feedback control of adaptive structures are considered and the oscillations are induced by the action of the blast loading. Wavelets provide a new tool for analysis, control, and identification of localized phenomena and vibrations. Instead of seeking to break down a signal into its harmonics, which are global functions that go forever, the signal is broken down into a series of local basis functions called wavelets. Each wavelet is located in a different place on the time axis. Several families of wavelet functions were studied. Haar, Meyer, Mallat, Daubechies, and Newland are in pattern recognition, image processing, turbulence, etc. This paper uses the Haar wavelets in order to perform the optimal control law with input voltage constraint and input power consumption. The influence of the inclusion of the excitations in the quadratic performance criterion of size and location of piezoactuator patches on the dynamic response of thin-walled beams subjected to blast pulses are studied.
Active noise and vibration control for a high-speed railcar: Rolling rig measurements
Authors: Schirmacher Rolf , Hölzl Georg , Scheuren Joachim
Published: July 2002

The feasibility of active noise and vibration control (ANVC) of the low-frequency interior noise (around 100 Hz in the case presented) of a high-speed railcar is studied. The car chosen for this study is the first generation of the German Intercity Express (ICE) trains. Based on the design of the car, the bogie, and the bogie/car body interface, an active control system combining some aspects of active vibration isolation and active structural acoustic control was proposed and studied by model experiments and simulations [Schirmacher et al., Proc. Active 97, 557–564]. Based on these results, an active system with four actuators fitting into the secondary suspension was installed at one bogie, and the whole railcar was tested at the rolling rig of Deutsche Bahn in Munich. Test drives on the rig cover speeds up to 250 km/h with and without railway line track simulation. For wheel harmonics in the critical frequency range, global sound-level reductions of more than 12 dB have been achieved in the whole passenger compartment, with peaks of more than 20 dB at single passenger seats. For dominant wheel harmonics, global reductions of 6–8 dB can be expected, averaged over the whole passenger compartment.
Linear and nonlinear responses to speech rate in left and right temporal cortex
Authors: Wise Richard , Bailey Dale , Leff Alex , Scott Sophie
Published: July 2002

Aspects of speech processing in the temporal lobes were investigated in a functional neuroimaging study using a parametric design, where the rate of hearing single words was varied. A previous study distinguished regions in left and right temporal cortex where activity varied linearly with rate (up to 90 wpm) from a single region, in the left posterior temporal cortex, where activity was maximal at 10 wpm [Price et al., Neurosci. Lett. 146, 179–82 (1992)]. A fMRI study of left and right primary auditory cortex (PAC) and posterior dorsolateral temporal cortex [Dhankhar et al., J. Neurophysiol. 77(1), 476–483 (1997)] showed a decline in activity at rates above 90 wpm. In the current PET study, speech rate was varied up to 180 wpm, and the consequent curves in activity were investigated for the shape of the consequent nonlinearity in activity. These curves are described and related to hypothesized hemisphere specialization in speech processing. This result raises important issues about the responsiveness of the auditory system in relation to the rate at which it can process speech input.
Brain function in spasmodic dysphonia: A functional MRI study
Authors: Kumada Masanobu , Mencl Einar , Pugh Kenneth R. , Constable R. Todd , Bell-Berti Fredericka , Honorof Douglas N. , Gracco Vincent L.
Published: July 2002

The symptoms of spasmodic dysphonia (SD) are caused by the hyperadduction or hyperabduction of the vocal folds, but its mechanism is unknown. The purpose of this study is to locate dysfunctional regions in the brains of SD patients by functional MRI (fMRI) and to identify the mechanism of this disorder. The extrapyramidal system works normally as a stabilizer of muscle activities. This hypothesis is that its dysfunction (especially in the basal ganglia and brainstem) causes instability of the activity of the vocalis muscle which induces symptoms (voice break, etc.). The data for four normal subjects have been obtained, and sessions for four SD patients are planned. The tasks are: isolated phonations of /a/ in chest register (Ch); isolated phonations of /a/ in falsetto register (Fa); and breathing naturally for baseline (Br). Subjects phonate in Ch and Fa to visual cues given every 2 s. Each scan consists of nine 20-second blocks of tasks (2 Chs, 2 Fas, 5 Brs), and is repeated four times with counterbalanced task order. Imaginary phonation scans for Ch and Fa, in which subjects just imagine phonation without actually setting the vocal cords into vibration, are also repeated four times.
Attention to auditory feedback during sentence production by speakers with and without stuttering
Authors: Barac-Cikoja Dragana , Squire Shrita , Ludlow Christy L.
Published: July 2002

As participants repeated a target sentence, their speech was processed in real time and fed back through the headphones either (a) unaltered, (b) spectrally altered to simulate alien origin, or (c) replaced by a recording of the target sentence triggered by the participant’s speech. White noise from bone conduction maskers, in addition to the speech from the headphones, masked air-conducted speech. Gaps 100-ms long were randomly inserted in speech feedback to participants as they uttered each sentence. Detection accuracy was compared across a group of fluent speakers and a group of people with mild to moderate stuttering. Error rates for each of the three feedback conditions were calculated across six repetitions of the five target sentences. While the incidence of errors was higher in the group with stuttering, the pattern of errors was the same for both groups: misses (undetected gaps) prevailed in the unaltered feedback condition; and false alarms (incorrect gap identifications) predominated under alien feedback conditions (i.e., the spectrally altered and the replaced speech). The role of voice familiarity in speech monitoring will be discussed.
The adaptive modified rhyme test
Authors: Zera Jan
Published: July 2002

This paper discusses an application of the adaptive maximum-likelihood procedure (MLP) [Watson and Pelli, Percept. Psychophys. 33, 113–120 (1983)] to speech intelligibility measurements conducted with the modified rhyme test (MRT) [House et al., J. Acoust. Soc. Am. 37, 158–166 (1965)]. The MLP procedure allows the experimenter to preset the target intelligibility at any value and determine the corresponding speech-to-noise (S/N) ratio. This makes it an efficient tool for estimating the change in the S/N ratio required to maintain identical intelligibility in different noise conditions of the communication channel. The MLP-MRT was tested on a group of 12 listeners. The S/N ratio corresponding to intelligibilities of 50%, 70%, and 88% was determined in five test runs of 30 items each. Subsequently, the S/N ratios estimated by the adaptive procedure were verified by measuring the intelligibility scores by a nonadaptive method. Results showed that intelligibility scores obtained by the nonadaptive method differed by less than 5% from the intelligibility preset in the adaptive procedure. [Part of the work was done as a collaborative project between NRC and the Defence and Civil Institute of Environmental Medicine, during the author’s stay with the Acoustics and Signal Processing Group, NRC, Ottawa, Canada.]
Requirements to signal processing for visualizing surfaces from three-dimensional ultrasound data sets
Authors: Sakas Georgios
Published: July 2002

Three-dimensional ultrasound can be regarded as the generalization of the traditional 2-D technique with the aim to provide a ‘‘tomographic’’ acquisition of the body interior, and moreover, to visualize surfaces of internal organs and pathology, such as fetuses, bone, liver, vessels, skin, brain, but also cysts, tumors, etc. The first requirement for visualizing a surface is obviously the ability of a system to provide mostly clear, sharply defined, high contrast surfaces of internal interfaces between tissue types. The presence of speckle (e.g., parenchyma within liver, amniotic fluid, etc.) greatly reduces the ability of presenting surfaces. ‘‘Ideal’’ surfaces from the visualization point of view have a small width (i.e., narrow transition zone between different tissues), are smooth, high contrast, continuous, gapless, and show the same gradient and average intensity. Although these requirements can hardly be fulfilled all at once, one wishes/expects that selective image processing can help overcome several of these difficulties. Numerous examples of this group’s previous works demonstrating all 3-D surface visualization drawbacks listed above, together with some image-processing-based improvement techniques proposed so far, will be presented.
Neural network-based spatial filtration algorithm for a 2-D microphone array
Authors: Czyzewski Andrzej , Lasecki Jacek
Published: July 2002

In order to process acoustic signals obtained from a 2-D microphone array, a neural network-based system was developed. The neural network provides a nonlinear filtration of acoustic signals transformed into the frequency domain. The neural network was trained in such a way that it is performing a spatial filtration of sounds arriving to microphones from various directions. It was trained in acoustically diversified rooms with phonemes edited from speech which were played back by loudspeakers placed at various angles in relation to the microphones. A standard error back-propagation algorithm (EBPA) was used in the supervised training procedures. The desired amplification was defined for each sound pattern. As a result, some sharp directivity characteristics were obtained. The results demonstrate that such a spatial filter ensures a substantial increase in the signal-to-noise ratio and a significant improvement in the intelligibility of speech obscured by background noise and by undesired signals coming from various directions. A comparison between the results obtained using the neural network algorithm and results obtained using some standard beamformer algorithms was also made. The developed algorithm details and results of spatial filtration based on the neural network approach are demonstrated. [Work supported by KBN, Poland, Grant No. 8 T 11E 03415.]
Time-dependent scattering from bubble clouds: Implications for the use of acoustic pulses
Authors: Clarke James W. , Leighton Tim G. , Heald Gary J. , Dumbrell Hugh A.
Published: July 2002

A theoretical model has been developed to investigate the ring-up times, or time taken to reach steady-state oscillation, of gas bubbles in fresh water. The model utilizes numerical solutions of the Herring–Keller bubble model and damping values after Prosperetti’s 1977 analysis to calculate the extinction cross-sectional area of a bubble as a function of time in response to a continuous harmonic sound field. The model has also been extended to determine the extinction cross-section area of multiple bubbles of varying population distributions assuming no bubble–bubble interactions. The results have shown that the ring-up time of a bubble is dependent on its closeness to resonance and the driving pressure amplitude. Investigation of various bubble populations has shown that the ring-up time of the resonant bubbles may be masked by the presence of large off-resonant bubbles and that high-amplitude sound fields enhance this effect. The implications of these findings for the use of acoustic pulses are explored. [Work supported by DERA.]
A time-domain path integral method for analyzing reflections from a rough sea surface
Authors: Forsythe S. E. , Piquette Jean C. , Badiey Mohsen , Simmen J.
Published: July 2002

Recently, experimental data were gathered for broadband (500 Hz–20 kHz) sound transmissions in shallow water over a period of seven days. The processed data form a good approximation to the impulse response of the environment, including direct signal paths, surface interactions, and bottom interactions, from a source to both local and remote receivers. Since the signals resulting from a single interaction with the ocean surface can be cleanly separated from other arrivals, these signals become a rich source of information about surface wave motion and thus about the state of the sea. To analyze the effects of surface waves (surface wave height, period, wave number, wave direction) on the received signal, including frequency dependence, a tool for efficiently calculating broadband response of a rough sea is needed. Instead of solving for the wave field at many frequencies and synthesizing the result into a broadband response using Fourier techniques, a direct computation of the response uses raylike techniques to sum over all significant paths in the time domain. For some problems, this technique is much more efficient than frequency-domain approaches such as PE or wave number integration, while providing the low-frequency accuracy that is only approximated by ray theory approaches. [Work supported by ONR.]
Surf zone breaking wave air entrainment and noise generation
Authors: Su Ming-Yang , Wesson Joel C.
Published: July 2002

During two field experiments conducted at CERC (Coastal Engineering Research Center) at Duck, NC in 1997 and 1998, NRL made simultaneous measurements of air void fraction and sound intensity due to wave breaking across the surf zone under various weather conditions with or without wind forcing. The void fraction sensors, wave pressure gauges, and hydrophones were deployed by two distinctly different methods. The first method used a new and unique swinging-bar which has the top end attached to a surface float, with its bottom end attached to a universal joint anchored in the sandy bottom. The second method used the CERC Sensor Insertion System (SIS), to place the instruments in the water at various points and depths along the 600-m-long pier at the facility. This paper presents the characteristics and statistics of the spatial and temporal variations of these void fraction measurements associated with surface wave profiles, and power spectra and time-frequency spectra of sound intensity under wave breaking. The corresponding relationship between the void fraction variation and sound intensity shall also be presented.
Good acoustics: A target for the new School of Architecture
Authors: Viveiros Elvira B.
Published: July 2002

A competition for a new building for the School of Architecture is being commissioned in Florianopolis, Brazil. The project involves classrooms for theoretical classes, ateliers, library, auditorium, laboratories, staff offices, and support rooms. It consists of a 6000-sq.-m building. The site faces a noisy road, which is bound to become even noisier as the whole area develops. The provisional existing building already presents inadequacies, as for instance lecturers have complained they need to stop talking while a lorry passes along. The paper presents the proposed solutions to acclimate the new school to its environment, as well as the project details to provide good acoustic quality for the different rooms. For instance, taking into account particularities of this kind of school, absorption mechanisms play simultaneous roles in the classrooms. As the projects being developed by the students need to be hung up for oral presentation, wooden panels were planned for the side walls. Acting as vibrating membranes, the reverberation time is adequate, whilst the panels hold the posters for presentations. Solutions to avoid noise break-in are also shown.
Discrimination of phantom targets by an Atlantic bottlenose dolphin (Tursiops truncatus)
Authors: Aubauer Roland , Au Whitlow W. L. , Pawloski Jeff L. , Pawloski Deborah A. , Nachtigall Paul E.
Published: July 2002

The ability to make fine distinctions in properties of targets is one of the outstanding characteristics of the dolphin sonar system. Behavioral experiments with these animals can reveal target echo features that can be used to model the biological sonar in order to evolve technical systems with equivalent capabilities. A phantom echo generator was developed in order to obtain programmable control over echo parameters in the time and frequency domains. Dolphin sounds are recorded with a hydrophone, transformed into the desired phantom echoes, and played back with a projector hydrophone. The signal transformation is based on the acoustic impulse response of a target and is executed on a DSP system in real time. In the first experiment the capability of a dolphin to discriminate between acoustically simulated phantom replicas of targets and their real equivalents was tested. Phantom replicas were presented in a probe technique during a materials discrimination experiment. The animal accepted the phantom echoes and classified them in the same way as it classified real targets.
Comparison of seafloor character as measured by calibrated vertical-incidence profiler and sidescan sonar
Authors: Fleischer Peter , Jans Wolfgang , Wood Warren T.
Published: July 2002

Sidescan sonar backscatter from a variety of continental shelf bottom types reveals considerable divergence from vertical-incidence reflection coefficients. Acoustic data are from a 300-kHz sidescan sonar and a calibrated, constant beam width, 10–50 kHz vertical incidence profiler, and are supported by extensive physical, geoacoustic, textural, and morphologic measurements. Bottom types include a wide range of quartzose and carbonate sands and silts, seagrass, coral heads, coral reef, and hardbottoms. The two systems show notable divergences over seagrass and carbonate hardbottoms, which produced low normal-incidence reflection coefficients but high backscatter from sidescan sonar, and smooth, packed sands, which gave high normal-incidence reflection coefficients but low sidescan backscatter. The divergences appear to be caused by bottom roughness. Narrow-beam, vertical incidence systems are subject to signal loss from out-of-beam scattering over rough bottoms, whereas roughness increases backscatter at the low grazing angles over which the sidescan system operates. Although both systems will accurately map bottom character, there is no direct correspondence betwen the two vis-à-vis bottom type. Therefore, to extend seafloor classification from vertical incidence profiling into an areal approach with sidescan sonar requires more than simple lateral extrapolation. [Work supported by ONR.]
In situ, laboratory, and modeled permeability of unconsolidated sands
Authors: Lavoie Dawn L. , Reed Allen , Briggs Keven
Published: July 2002

Bulk physical sediment properties, especially permeability, are required to predict sediment geoacoustic and geotechnical behavior. Of the variables controlling permeability in surficial sediments, pore space distribution is probably the most significant. The objective is to quantify the relationship between sediment microfabric and sediment flow properties. Relatively undisturbed samples were collected by divers from the upper 25 cm of seafloor from several locations on the Florida shelf and near Bimini in the Bahamas. The undisturbed sediment microfabric was maintained by impregnating the samples using a polyester resin. Sediment microfabric was examined using petrographic and scanning electron microscopes. Representative images were scanned and analyzed using Image Tool and Image Tool Plug Ins. Using erosion-dilation analysis, the 2D imaged pores and pore network were defined and quantified. CT images were used to determine sediment isotropy and to generate 3D structural images, which were used as input to effective medium theory to predict single-phase flow within the sediment. The modeling results are compared to laboratory-measured permeability from the same samples, and with permeability measured in situ using a falling head permeameter. [This work was supported by the Naval Research Laboratory.]
Transfer of an exact number of molecules into cells by shock waves
Authors: Delius M. , Adams G.
Published: July 2002

Shock wave application to cells in vitro causes a transient increase of the permeability of the cell membrane which does not lead to cell death. The transfer of molecules into the cytosol was quantified with florescein dextrans by flow cytometry. It was much higher than the uptake by endocytosis. It did not change over the next hours; there was no efflux. It depended linearly on the dextran concentration in the medium. In addition, transfer of a low number of dextran molecules of high molecular weight was equal to a high number of low weight. In conclusion, shock wave transfer reflects directly the amount of fluid transferred. It is in the femtoliter range. The number of molecules acoustically transferred by a certain fluid volume into a cell depends on their concentration in the medium. The protein gelonin was used to transfer different numbers of molecules into the cytosol and to assess the cell proliferation. Acoustic transfer of a single molecule or of any other defined number of molecules into the cell is a simple method to assess dose-response effects. It might be widely applied in disciplines such as physiology, biochemistry, and drug design.
Aspects of pressure pulse lithotripter measurements
Authors: Ueberle Friedrich
Published: July 2002

Although pressure pulse waves have been used as the standard treatment of kidney stones (ESWL) for the last 15 years, the relevance of their different physical parameters is not fully understood. The new approach of tissue treatment for pain reduction (ESWA, ESWT) raises even more questions. In 1998, the IEC document 61846 ‘‘Ultrasonic-pressure pulse lithotripters—Characteristics of fields’’ was internationally accepted. It contains the descriptions of all the parameters which may be measured, as well as the different hydrophone types which may be used. Additional work was done, e.g., by the FDA and in the ‘‘German society for shockwave lithotripsy’’ (DGS) to define a standard set of pressure pulse data, measured according to the IEC standard. The standard parameters may be measured using different hydrophone types and using either (only) the positive parts of the waves or the complete wave, including rarefaction parts for the calculation of energy parameters. Choosing a hydrophone capable of serving the demands of lifetime, signal confidence (including time parameters and rarefaction pressure), as well as cost efficacy is the most delicate task. Various aspects necessary for the interpretation of standard parameters measured using different hydrophones will be discussed.
Generation of a very high pressure pulse at the surface of a sandwiched piezoelectric material
Authors: Sferruzza Jean-Pierre , Cathignol Dominique
Published: July 2002

New clinical concepts in lithotripsy demand small size shock heads. Reduction of piezoelectric shock head is only possible if accompanied by a corresponding increase of the pressure generated at the surface of each transducer, so that the total pressure at the focus remains the same. Because the pressure generated by a transducer is proportional to the electric field applied between its two electrodes, a higher pressure could be generated by using greater electric fields. Nowadays, the value of the usual fields is no more than 2 kV/mm and the generated pressure at the surface is about 10 bars. Unfortunately, higher pulsed fields applied on the transducer lead to breaking phenomena. For the first time, a proposal is presented to increase the pressure using sandwiched transducers, which are a combination of several stacked transducers excited at such times that the pressure waves generated by each one are fully added at the interface transducer–propagating medium. This new and patented technique has been successfully tested. More than 30 bars were obtained with a two-layer transducer each 5-mm thick, and working under an 8-kV excitation voltage. Using this new elementary transducer a piezoelectric shock head of only 20-cm diameter is expected.
Acoustical analysis on the performance of digital hearing aids
Authors: Qi Yingyong , Dittberner Andrew
Published: July 2002

The acoustic spectral distances were computed for phonemes, /p/, /t/, and /k/ recorded under a variety of recording conditions, which include: a low (50 dB SPL) and high (80 dB SPL) signal level, a quiet and noisy listening environment, and no processing and processing by three different signal-processing algorithms of a hearing aid. All recordings were obtained using a Zwislocki coupler inside the Knowles Manikin for Acoustic Research. The purpose of this study was to determine whether the acoustic distance between confusable phonemes can be used to evaluate the performance of speech-processing algorithms used in nonlinear, digital hearing aids. The acoustic distance was the rms amplitude difference in the short-term spectra between any two speech segments after they were optimally aligned in time. It was hypothesized that: (1) There would be a significant reduction of acoustic distance among the selected phonemes when speech signals were filtered to simulate a given hearing loss configuration. (2) The use of a hearing aid would significantly alleviate the reduction of acoustic distance among these phonemes. Results, in general, were supportive to these hypotheses. It is, therefore, feasible to assess the information-processing function of a nonlinear, digital hearing aid using an instrument-based approach.
The implementation of ISO/IEC guide 25 for acoustical standards at NRC Canada
Authors: Wong George S. K. , Wu Lixue
Published: July 2002

Since the publication of ISO/IEC Guide 25, national acoustical measurement laboratories are under pressure to follow the recommendation of the Guide to update the calibration procedures to ensure confidence in the calibration services offered. The uses of the Guide (currently under revision as DIS 17025: General requirements for the competence of testing and calibration laboratories) promote cooperation between laboratories, acceptance of measured data in industries and in the harmonization of standards and procedures. In the international scene, the acceptance of calibration and test results between countries will ease the removal of nontariff barriers to trade. This presentation provides a brief discussion on the requirements and the strategy used to enhance the acoustical standards program at the National Research Council.
Presenting noise information to community decision-makers
Authors: Dubbink David T.
Published: July 2002

Resolving community noise problems requires not only accurate data about noise impacts, but also demands an effective means of communicating this information to decision-makers. The Interactive Sound Information System (ISIS) is a ‘‘new media’’ package designed to explain and demystify the complex metrics used to describe noise impacts. Central to the ISIS package is the idea that ‘‘real’’ noise examples, shaped to reflect local situations, are the very best way to build an understanding of noise management issues. The system has been used effectively by governmental agencies and noise management specialists as a means of delivering information that is both understandable and technically accurate. The United States Air Force, in association with the FAA, has supported development of an expanded version of the program that incorporates state-of-the-art multimedia technology. The new version of the program is designed for a wide audience, and its operation does not demand technical expertise. It uses the 3-D viewing capabilities of the Virtual Reality Modeling Language (VRML). The updated software is built on the Java platform, giving the package both modularity and Internet capabilities. The program links to airport and highway noise prediction models.
Noise abatement in urban areas
Authors: Beeks A. A. F. M. , Dittrich M. G. , Kooijman P. P.
Published: July 2002

Two studies on noise abatement in urban areas, performed for the Dutch Ministerie of Transport (SSZ program), are presented. The first is a feasibility study on noise reduction of a range of vehicles. Buses and lorries were found to have comparable noise levels, whereas delivery vans and taxis were found to be much quieter. Specific noise sources can be high. More stringent (European) regulation or governmental stimulation measures are required. A survey was held amongst 396 inhabitants in two cities. Most noise disturbance was shown to be caused by buses (low-frequency acceleration noise). The second study was on noise disturbance during goods delivery to shops. This was initiated after the extension of business hours and the introduction of stricter regulations (60 dB peak limit). Current measured peak A-weighted noise levels at 7.5 m were found to vary between 60 and 95 dB. The study concluded that noise control measures for most sources are technically achievable within three years. Initial estimates indicate 10%–20% higher investment on vehicles and handling equipment. Lorry diesel engine noise is about 15 dB too high. Well-designed quiet electric traction systems are a quieter alternative.
Experimental study of rasping noise in internal combustion engine exhaust systems
Authors: Ayadi Mondher , Frikha Slaheddine , Hennion Pierre Yves , Coulon Jean Michel
Published: July 2002

The abnormal noise, known as rasping noise by several exhaust muffler designers, is a metallic intermittent noise which irritates the ear and has an adverse effect on vehicle marketability. It occurs in small cars having no more than two boxes in their exhaust systems. This phenomenon is highly noticed during a rapid acceleration or deceleration in cold conditions. However, it is sharply attenuated when the exhaust system is warmed up. An experimental study has been undertaken. Several exhaust systems, ranging from a simple pipe to a complete exhaust line, are tested. Pressure measurements in the line are performed by piezoelectric transducers. The tail pipe noise measurements are performed by a microphone. It has been observed that, unlike the usual exhaust noise that contains essentially second and fourth orders, the perception of the so-called rasping noise is associated with high-frequency components in the signal and needs higher-order analysis to be fully characterized. The experiments also show the steepening of the waves when rasping noise is listened. The high axial temperature gradient causes an increasing of that effect and probably a generation of shock waves which excite the main muffler and cause the metallic noise.
Efficient boundary element calculations using thin-plate acoustic elements
Authors: Fahnline John B. , Koopmann Gary H.
Published: July 2002

Thin-plate elements are commonly used to represent structural components whose thicknesses are much smaller than the structural wavelength. This simplifies the analysis, because otherwise several elements are required to represent correctly the strain distribution through the thickness, leading to much larger models. Thin-plate elements also have advantages when they are used in acoustic boundary element calculations. By using dipole sources at the midline of the elements to generate the basis functions for the acoustic analysis, the boundary condition can be enforced such that the opposite sides of the plate are forced to move together. The surface velocity boundary condition then only has to be enforced over one side of the elements (even though both sides are in contact with the acoustic medium). Mechanical radiation impedance calculations can also be simplified because the dipole source basis functions create the same pressure field on opposite sides of the plate elements and thus impart no force to the structure. The only exception is for ‘‘self-element’’ terms, where the dipole sources create equal, but opposite, surface pressures. Several example problems are used to validate the calculations, including a vibrating strip, a transversely oscillating disk, and a cantilever plate.
Improvement of the lateral resolution of finite-size hydrophones
Authors: Boutkedjirt Tarek , Reibold Rainer
Published: July 2002

In recent years, there has been an increasing number of ultrasound applications which utilize frequencies well above 10 MHz. Piezoelectric hydrophones are commonly used for the characterization of the respective fields. With the exception of specially designed laboratory devices, limits are set to the hydrophones currently available due to their finite size. Instead of measuring the acoustic pressure at a point, these devices furnish a value integrated over the sensitive aperture. The adverse averaging effect is particularly prominent in the Fresnel zone of the sound field and at frequencies above 10 MHz, where the aperture dimensions are of the order of several acoustic wavelengths in water. This problem can be solved by numerically deconvolving the aperture function from the observed response of the finite-size receiver. The efficiency of the deconvolution process is shown for both numerical simulations and experimental investigations. Special regard is paid to the methods of noise reduction by means of averaging, smoothing, and filtering.
Elastic modules modification and phonon focusing in zinc oxide
Authors: Zubrytski Uladzimir V.
Published: July 2002

Despite the direct observations of the acoustic waves focusing in different solids [J. P. Wolfe, Phys. Today 48, 34–40 (1995)], the properties of the phonons’ propagation and possibility of these control have not been studied in hexagonal media. To check this statement [U. V. Zubrytski, Z. Tekhn. Fiz. 67, 59–64 (1997)] and obtain striking demonstrations of drastic changes in the phonon focusing patterns at elastic properties, modification of such solids’ phonon focusing is simulated in zinc oxide grown by the hydrothermal method, in the vapor state at and without doping with lithium, and magnetron sputtering, in this paper. Simulation shows that elastic modules modification within the accuracy of available experimental data causes both sharp increasing of the intensities and defocusing of the individual phonon modes. Quantitative dependences of the effect have been established for bulk acoustic waves in the samples investigated. The findings allow one to elaborate not only the equilibrium but the dynamic method to control selectively both intensities and angular distributions of the acoustic energy fluxes in the crystals and thin layers as well. Besides, the elastic constants recovering from the measuring of the focusing factor can be realized. [Work partially supported by the Belarusian Republican Foundation for Fundamental Research.]
Gap detection thresholds of Laura cochlear implant users for complex patterns of stimulation
Authors: van Wieringen Astrid , Wouters Jan
Published: July 2002

The ability to detect silent intervals on single and multiple electrode pairs was examined for different types of speechlike stimulus configurations in four postlingually deafened Laura cochlear implantees. Gap detection thresholds were determined in function of stimulus complexity, spectral disparity within and across the markers bounding the gap, stimulus asymmetry (cf. consonant–vowel versus vowel–consonant patterns), and pulse rate. All stimuli were roving in duration from 200 to 600 ms to ensure that subjects could not use overall duration as a cue. In addition, all the experimental conditions were balanced in loudness. Preliminary results have shown that stimulation of single electrode pairs yields smaller gap detection thresholds than stimulation of multiple electrode pairs, and that gap detection thresholds on multiple electrode pairs increase as the distance between the electrodes increases. Subsequent measurements illustrate that gap detection thresholds across multiple electrode pairs can decrease substantially after sufficient training, and that the spectral composition of the stimulus only affects gap detection when the spectral disparity occurs across, not within, markers. These findings, together with others concerning stimulus asymmetry and pulse rate, are of fundamental importance to understand the biophysical limitations of electrical stimulation related to the coding of sound by the auditory system.
Acoustics tools for ocean pollution research and monitoring in the MAST program
Authors: Ollier Gilles
Published: July 2002

The monitoring of ocean pollution as well as coastal waters monitoring and management is a growing interest of the European Commission (EC). Among several methods, acoustical measurements remain the preferred one for insight observations. In the framework of the MAST program (Marine Science and Technology, Directorate General for Research, DGXII), the EC has supported several programs dealing either with the understanding of physical phenomena and the development of new acoustic instruments or with the development of integrated systems (and mainly survey ROVs) where the acoustics plays an important role for sediment characterization. Among others, the following projects will be presented: TRIDISMA (three-dimensional sediment transport measurement by acoustics), MAUVE (miniaturized and reconfigurable instrument for multipurpose survey with a mini autonomous underwater vehicle; includes a multifunction acoustical unit for the survey of coastal waters), ARAMIS (advanced ROV package for automatic mobile inspection of sediments; includes bathymetric sonar, obstacle avoidance sonar and vertical sounder), and BIOSONAR [sonar technology for monitoring and assessment of benthic communities; acoustic determination of bottom type (sand, eelgrass, mussels,...)]. The paper will review the past research activity of the EC-funded projects in pollution monitoring and will show the emphasis of the fifth framework program in this area.
European Committee for Medical Ultrasound Safety (ECMUS): Tasks and activities
Authors: Rott Hans-Dieter
Published: July 2002

The European Committee for Medical Ultrasound Safety (ECMUS, ‘‘The Watchdogs’’) is an interdisciplinary group of European scientists who are permanently engaged in monitoring the safety of diagnostic ultrasound. The task of the Watchdog Group is to inform the members of the European Federation of Ultrasound in Medicine and Biology (EFSUMB) about potential risks of ultrasound and to give advice for its appropriate use. The group meets at least once a year. Its activities include literature reviews, publication of tutorial articles and guidelines, organization of EFSUMB Congress safety sessions, and preparation and publication of a safety statement which is regularly reconfirmed or amended. The Watchdogs can be contacted through the EFSUMB office in London [http://www.efsumb.org/ecmus.htm] or directly to any of the members who are prepared to comment on any question concerning safety issues of medical ultrasound. The present Watchdog members are: Prof. Philippe Arbeille, Physicist in Tours, France; Prof. Ulrich Cobet, Biophysicist in Halle, Germany; Dr. Francis Duck, Physicist in Bath, UK; Prof. Karel Marsál, Obstetrician Gynecologist in Lund, Sweden; Prof. Hans-Dieter Rott, Human Geneticist in Erlangen, Germany; and Dr. Kjell Salvesen, Obstetrician and Epidemiologist in Trondheim, Norway.
Temperature elevation generated by ultrasound in soft-tissue, bone, and transcranial phantoms
Authors: Wu Junru
Published: July 2002

Ultrasound imaging has been widely used in medicine and many new procedures are being developed to obtain images of regions in a human body once considered beyond the reach of ultrasound. To address the safety issue related to the thermal effects of ultrasound, the American Institute of Ultrasound in Medicine and the National Electrical Manufacturers Association have developed simple equations to calculate thermal indices (TI) that indicate the worst-case temperature elevations for various clinical situations. To experimentally verify the equations, soft-tissue, bone, and transcranial phantoms were constructed. The measured results of temperature rise in the phantoms generated by diagnostic ultrasound were compared with various thermal indices. In general, TI underestimated temperature rise in situ. The disparity can be attributed to transducer surface heating.
Boundaries to effective acoustic output regulation from acoustic saturation
Authors: Duck Francis A. , Starritt Hazel C.
Published: July 2002

Acoustic saturation limits the pressure amplitude which may be reached at any position in an ultrasonic beam. The saturation pressure, psat, is a function of acoustic frequency, distance from the source, and the acoustic nonlinearity parameter. It is independent of the source pressure. An approximate expression has been used [Naugol’nykh and Romanenko, Sov. Phys. Acoust. 5, 191–195 (1959)] to predict psat at the focus of spherically focused medical diagnostic beams in a lossless medium. psat typically lies in the range 1–10 MPa, lower values being associated with higher frequencies and longer focal depths. Mechanical index and spatial-peak intensities are also subject to saturation effects, being calculated from acoustic pressure. A significant range of conditions exist for which acoustic saturation prevents MI, and derated I(spta) and I(sppa), from exceeding the regulatory limits set by the Food and Drug Administration in the USA. Action limits set by IEC 61157 are sufficiently low to be unaffected in the majority of cases. It is concluded that the existence of acoustic saturation presents a strong argument to review present procedures for regulating acoustic output from diagnostic ultrasound equipment.
Surface acoustic waves and devices—A brief overview
Authors: Robinson Harold C.
Published: July 2002

This paper will provide a basic introduction to surface acoustic waves and devices. Surface acoustic waves have been employed in a broad spectrum of devices, from filters and oscillators used in communications, to chemical and biosensors. This tutorial will detail the fundamentally important properties of surface acoustic waves which make them useful in devices. The principal methods of generating them will be discussed. A broad overview of their areas of application, as well as the types of devices which are possible using them, will be given.