bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulation and optimization of smart piezoelectric structures
Authors: Gabbert Ulrich , Weber Christian-Toralf
Published: July 2002

In this paper an overview about a finite-element-based simulation tool for smart structures is given, which includes also optimization procedures (e.g., for sensor/actuator placement) as well as control strategies. The focus of the paper is on piezoelectric materials (wafers and fibers) as active components, which are controlled by electric fields and consequently, the coupled electro-thermo-mechanical field equations have to be solved. The element library contains 1-D, 2-D, and 3-D multifield finite elements as well as special layered elements to simulate thin-walled structures with different layers of passive and active materials based on a layerwise constant shear angle theory. A substructure/superelement technique can be used in static as well as dynamic applications. In the optimization of actuator distributions a discrete-continuous optimization procedure will be presented, where the actuator positions at the structure are described by dicrete 0-1 variables, and the control parameters are included as continuous variables. Mathematical solution algorithms for nonlinear, mixed optimization problems are used to solve the optimization problem. Test examples (e.g., active vibration damping to reduce noise radiation) and comparisons with experimetal results will be presented to discuss the quality of the finite-element simulation and optimization tool.
Active noise reduction for steel bridges
Authors: Berkhoff Arthur P. , de Beer Fred G. , Looijmans Karel N. H. , van Overbeek Michiel W. R. M. , Doelman Niek J.
Published: July 2002

Experimental and computational results are given for active control systems minimizing sound radiation from steel bridges for trains. The performance of the active systems with respect to noise reduction, convergence, stability, and actuator requirements is described. At frequencies above approximately 300 Hz passive means can be used to reduce the radiation of noise from railway track. At lower frequencies, however, passive means to reduce acoustic radiation are not possible due to various reasons. Additionally, the main source of acoustic radiation at low frequencies is the steel bridge instead of the railway track. Therefore, the active noise control system for the steel bridge is based on the active isolation of track vibration by minimizing the mean-squared force between the steel bridge and the support for the rails. This is accomplished by controlling the distance between the rail supports and steel bridge with piezoelectric stack actuators. Transfer functions, load impedances, and actuator characteristics obtained from finite-element analysis and measurements lead to noise level reductions of 10 to 20 dB, depending on the control strategy and the available computational resources of the real-time implementation.
A coupled finite-element–normal modes expansion method to model Lamb waves generated with integrated transducers in composite plates
Authors: Moulin Emmanuel , Assaad Jamal , Delebarre Christophe , Balageas Daniel
Published: July 2002

The use of miniaturized piezoelectric transducers integrated to a host composite material could enable the development of an on-line ultrasound health monitoring system for composite structures. Preliminary testing has already demonstrated the suitability and practical feasibility of this kind of integrated system, but a better control of these features now seems to be necessary. And especially, since the exploited ultrasonic vibration modes for plate-shaped structures are Lamb waves, the generation of desired Lamb modes should be mastered. Therefore, an original modeling approach has been developed, in order to help to design and optimize these ‘‘smart materials.’’ This modeling technique aims at determining the amplitude of each Lamb mode excited in a composite plate with surface-bonded or bulk-embedded piezoelectric elements. It consists of a coupling of the numerical finite-element method (FEM) and the normal modes expansion method. Indeed, a limited finite-element mesh of the transducer and its close vicinity is built. Then the numerically computed mechanical field is introduced as a forcing function into the normal modes’ equations. In addition, the adequacy and accuracy of this modeling method have been experimentally demonstrated by using composite specimens containing small integrated piezoelectric elements.
Analysis and synthesis of F0 contours by linear prediction coding
Authors: Mersdorf Joachim J. , Schmidt Kai U.
Published: July 2002

At present, there is still a lack in integrated methods for automatic analysis, coding, prediction, and generation of F0 contours. The use of linear prediction coding could be a first step in that direction [Mersdorf et al., ESCA Tutorial and Research Workshop on Intonation: Theory, Models and Applications, 235–238 (1997)]. The approach allows an automatic extraction of different parameters (e.g., accents) from intonation contours by means of appropriately simplified residual functions using rectangles. Such a signal approximation can be regarded as an excitation signal for prosodic accents and sentence mode. In that source-filter approach [cf. H. Fujisaki, in The Production of Speech (Springer-Verlag, New York, 1983), pp. 39–55] the resulting filter coefficients can be interpreted either as physiological parameters or as individual features in the intonation shape. The method was developed for both prosodic data analysis and acoustical contour resynthesis. Its structure is easy to describe and allows a very simple editing and modifying by shifting position, length, and height of typical rectangles. Furthermore, accents can be detected automatically at positions where the sign of the approximated rectangles changes. Perceptual evaluation indicated that the approximated and resynthesized F0 contours sound very natural.
Acoustical correlates of near-term suicidal risk
Authors: Özdaş Asli , Shiavi Richard G. , Wilkes D. Mitchell , Silverman Marilyn K. , Silverman Stephen E.
Published: July 2002

In the course of many years of clinical work in emergency rooms and office consultation with suicidal patients, clinicians have often successfully predicted suicidality based on the vocal patterns of the patients, independent of the content. Vocal sound and clinical substance reciprocally augmented each other in determining the near-term risk [M. K. Silverman and S. E. Silverman, ‘‘From sound to silence: A preliminary investigation of the use of vocal parameters in the prediction of near-term suicidal risk,’’ submitted to J. Med. Psychotheraphy]. Vocal patterns heard as representing a ‘‘hollow,’’ ‘‘toneless’’ sound were designated unanimously as the most compelling feature in suicidal voices. Motivated by qualitative descriptions of experienced clinicians, a quantitative study was carried out that investigated the acoustic correlates of near-term risk. The audio tapes selected for this research were suicide notes left on tapes donated by survivors, recordings of several patients who had been hospitalized, and recordings of 911 suicide in progress calls. This research is concerned with realistic speech data encountered in real-life situations due to the inability to study suicidal behavior in any kind of controlled setting. To compensate for spectral variability introduced by different recording environments, robustness techniques such as long-term mean removal and frequency warping were utilized. The relative significance of resonant frequencies and frequency bands in terms of their ability to predict the near-term suicidal risk was evaluated. Preliminary results suggest that the frequency spectrum patterns of the suicidal voice may have utility in the assessment of near-term risk.
Cross-modal integration in speech and nonspeech tasks
Authors: Weisenberger Janet M. , Kreidler Sandra M.
Published: July 2002

Studies of audiovisual speech perception show that both modalities contribute to the speech perception process. One salient example of this is the McGurk effect, in which visual /ga/ and auditory /ba/ might produce the fused percept of /da/. The present study investigated whether similar multimodal integration occurs for tactile–visual presentation via tactile speech perception devices, and whether these integration effects are specific to speech, or can also occur for nonspeech stimuli. The first experiment tested visual, auditory, tactile, and multimodal presentation of speech and nonspeech stimuli. Results indicated McGurk-type integration effects for both audiovisual and tactile–visual speech tokens, as well as some evidence of similar effects for nonspeech stimuli. Overall levels of tactile–visual integration were lower than audiovisual levels, possibly because of minimal subject training with the tactile aid. A second experiment provided two months of tactile aid training prior to integration testing. Preliminary results show an increase in McGurk-type integration for tactile–visual presentation. Overall findings suggest that the integration process is not restricted to audiovisual presentation. [Work supported by NIH.]
Method for the development of sentence materials for efficient measurement of the speech reception threshold
Authors: Versfeld Niek J. , Daalder Laura
Published: July 2002

Due to technological advancements, modern hearing aids may have many adjustable parameters, multiple memories, and the ability to house all sorts of signal-processing algorithms. To enable a systematic evaluation of the speech intelligibility for a variety of hearing-aid settings, large sets of speech materials are required. This paper reports on the creation and evaluation of a set of 1272 sentences uttered by two male and two female speakers. Two subsets were formed (one for a male speaker and one for a female speaker) to enable efficient measurement of the speech reception threshold in stationary speech-shaped noise. Each subset consists of 39 lists, each comprising 13 sentences. The properties of the new subsets are comparable to the existing sets that are used in clinical practice. [Work supported by the Heinsius Houbolt foundation.]
The learning of tactile syllables as reflected by blink rate and skin conductance variations
Authors: Arnhold Thomas , Piroth Hans Georg
Published: July 2002

In a series of experiments the learning of tactile speech has been investigated. The experiment to be reported was concerned with the role of physiological measures in interpreting perceptual stimulus processing. Five untrained participants underwent seven sessions of an identification test on six tactile syllables. The electrocutaneous stimuli representing three fortis and three lenis fricatives followed by a schwa were constructed as dynamical patterns and delivered to the left forearm (place of articulation from labial to velar: distal to proximal stimulation, fortis patterns moving faster than lenis patterns). Correct and incorrect answers as well as skin conductance reactions (SCR) and eye blinks were registered. For statistical analysis SCR-peak amplitudes and blink rate (BR) were calculated from stimulus onset to end of interstimulus interval. A MANOVA on SCR and blink rate shows significantly decreasing SCRs and increasing BRs over sessions. BR is higher in the case of correct identification. On the other hand, SCRs reveal a main effect of the stimulus factor based on higher amplitudes for front (distal) consonant equivalents. BRs (increasing with learning) are interpreted as reflecting cognitive activity, whereas SCRs (habituating over sessions) seem to represent orienting behavior.
Application of the continuous wavelet transform to the angular location of jet aircraft
Authors: Ferguson Brian G. , Lo Kam W.
Published: July 2002

For a fast moving source and widely spaced sensors, the passive wideband cross-correlation method for time delay estimation requires compensation for the relative time scaling between the received signals, otherwise the time delay estimates will be in error. Passive wideband cross correlation with differential Doppler compensation is equivalent to evaluating the continuous wavelet transform, which is an operation that transforms a function (represented by the output waveform of one sensor) by integrating it with time-scaled and time-delayed versions of some kernel function (represented by the output waveform of the other sensor). When the signal-to-noise ratio is high, the coordinates of the wavelet transformed global maximum provide reliable estimates of both the time delay and the ratio of the time scales of the signals received by the two sensors. The wavelet transform is used to process real acoustic data recorded from an orthogonal configuration of three microphones during the low altitude transit of a jet aircraft. The resulting time delay estimates are used to calculate the variation with time of the azimuth and elevation angles of the aircraft during its transit.
Software for estimation and processing simulation of microphone line arrays
Authors: Sevastiadis Christos , Chamzas Christodoulos C. , Kalliris George M. , Papanikolaou George V.
Published: July 2002

Software for estimation and processing simulation of microphone line arrays was developed, based on the fundamentals of sensor array theory and the basic concepts governing the array beamforming. Periodical, nonperiodical, and logarithmic microphone line arrays can be designed in a convenient way. Spatial structures, directivity patterns, and other properties of the microphone arrays are shown and examined diagrammatically. Optimization of the microphone array directivity index through the entire audio spectrum, using the logarithmic design and the apropriate filters, is shown as well. All properties can be easily examined and dynamically changed via a useful user interface. The designed microphone arrays can also be simulated using sound recordings of a single microphone or WAV files in PCM format. The program’s output is an audio processing simulation of the acoustic field which can be accessed through WAV file registering. This stand-alone, fully adjustable simulation software can be a user-friendly tool in understanding the basic concepts of the microphone array design theory.
Evaluation of various infrasonic array detectors
Authors: Smart Eugene
Published: July 2002

Several signal detectors are evaluated for infrasonic array data: (a) power detector that reviews a suite of array beams; if the mean square excursion in the window exceeds that of a longer preceding interval by an arbitrary threshold factor, a detection is declared. (b) Time domain F-detector, similar to the power detector, except that F is the detection criterion; F is proportional to the estimated S/N ratio. (c) f−k detector, similar to the time domain F-detector, except that it operates in the frequency–wave number domain. (d) Closure detector: cross-correlation lag times minus delay times of the best-fitting plane wave approach zero when a plane wave is present. Statistical distributions of waveform characteristics critical for signal detection are measured in a large, representative set of infrasonic data covering all hours of the day, four seasons of the year, and various geographic locations. The measurements are required for modeling detector performance: (a) The power detector uses data preceding the detection window to estimate the expected mean square excursion in the window itself, assuming continuity. The statistical distribution of such estimates is measured. (b) The mean-square excursion in a randomly chosen time window varies from channel to channel in real data. The statistical distribution of such variation is measured.
The influence of marine surface films on underwater sound
Authors: Pogorzelski Stanislaw
Published: July 2002

Essential characteristics of wind-generated ambient noise at sea depend on a few aerodynamic parameters of the sea surface–atmosphere interaction process. The film smoothing effect attributed to a reduction of the friction velocity and wind wave growth rate is shown, for model marine films, to be expressed in the corresponding changes of the sound-level intensity versus wind speed and frequency characteristics. Naturally generated ambient noise in the ocean is also created by breaking waves, resonating gas bubbles, spray, precipitation, or solid impacts, and has particular features. The spectrum of rain shows a peak at 13–15 kHz with the spectral level SL, in dB, linearly dependent on the log rain rate. The effect of a monomolecular film covering the surface exposed to splashing water droplets, uniformly distributed, and modeled as incoherently radiating dipoles, is evaluated assuming the Marangoni damping mechanism of surface disturbances by a viscoelastic film. The result is a pronounced reduction of SL beneath the film by 10 log K, 3–20 dB, for realistic systems, where the damping ratio K is a complex function expressed by the surface activity, elasticity, concentration, and diffusional coefficient of surfactants composing the film.
The influence of identical room dimensions on the sound insulation at low frequencies
Authors: Kropp Wolfgang , Kihlman Tor
Published: July 2002

At low frequencies the sound insulation between rooms is only valid for the specific case under consideration as shown in works by different authors. The expression ‘‘low frequencies’’ implies a frequency range where the rooms’ dimensions are comparable with the wavelength of sound in the rooms (i.e., normally below about 250 Hz for normal rooms). Both theoretical studies as well as experimental studies in the laboratory show that there is a substantial decrease of the sound insulation when the dimensions of the sending and receiving rooms coincide. The question arises if this decrease of the sound insulation can also be observed for the sound insulation of partitions in the field. The results are often biased by other effects such as flanking transmission or smaller differences in the fabrication of the partitions. By means of statistical studies field measurements are analyzed to show the influence of the room dimensions on the sound insulation in the field. To avoid the deterioration of the sound insulation, changes in the dimensions would be required which do not allow for symmetrical building designs as it is often preferred in practice.
A plausible mechanism of acoustic click production in the dolphin
Authors: Dubrovsky Nikolai A. , Giro Lyudmila R.
Published: July 2002

A mechanism of click production has been studied. Three steps were considered: experiments with Tursiops truncatus, calculations to determine the source position, and physical and mathematical models for simulation of a physical mechanism of click production. It was found that the acoustic source is situated in close proximity of the right nasal plug. A physical model of a nasal passage was composed of a rubber tube open on one end and connected to a pressurized gas container on the other. A rubber ring was put on the underwater part of the tube, which blocked the air passage at small access pressure. By varying this pressure of the elastic properties of the tube and the ring, one can put the model in a self-oscillation mode of vibrations. The displacement curve (DC) of the ring has a triangle shape and duration of about 700 mks. There were three noticeable acoustic pressure clicks with duration of 50–80 mks, phase-locked to pronounced changes in the DC. A mathematical model was developed to explain the origin of clicks and their locking to the bends of DC. The characteristics of clicks formed by the models are similar to the clicks of the dolphin.
Why do whales communicate at the frequencies they do? Lessons from underwater acoustic signal processing
Authors: Heaney Kevin D. , Clark Chris
Published: July 2002

The combination of frequency-dependent attenuation of acoustic energy and the ambient noise field of the deep ocean provides a window of opportunity for acoustic communication ranging from 10 to 1000 Hz. Why do pelagic whale species choose to use center frequencies between 20 and 50 Hz rather than higher frequencies in the window of opportunity? It is not a size limitation, because similar size whales which reside nearby in shallow water have center frequencies of propagation from 400 to 700 Hz. Experience in underwater signal processing has shown that internal wave scattering can be significant for acoustic frequencies above 50 Hz. Here the postulate is presented that deep-water whales (blues and fins) have chosen to send acoustical signals at 20 Hz to minimize internal wave scattering of their acoustic energy. The implications to range of detection will be made from a signal processing point of view and the impact that this would have on marine mammal biology will also be presented. Similar arguments, though based on different physics, will be employed to discuss the shallow-water whales’ (bowhead, humpback, gray) choice of 400 Hz.
Aspects of near-real time acoustic sediment characterization
Authors: Jans Wolfgang , Wood Warren T. , Smith Eric
Published: July 2002

Quantitative near normal incidence acoustic measurements were made with a calibrated, broadband, narrow-beam echo sounder at a variety of natural sediment sites along the Florida coast. The measured reflectivity of the water–sediment interface along track lines was converted into a map-view image, using recently developed interpolation and visualization software. The computed reflectivity was then compared to sediment samples and visual observations recovered from the same area. The measurements demonstrated that areas of different bottom type within a site could be clearly distinguished using acoustic techniques. At some sites, conventional expectations that softer sediments show a lower reflectivity than harder sediments were fulfilled. However, at other sites, the expectation superficially appears to be violated presumably due to the influence of bottom roughness. The presence of turtle grass also reduces reflectivity. To gain an understanding of these findings, histograms of the received echo signal and frequency spectra for different areas have been compared. The rapid 2.5-D visualization of bottom reflectivity and bathymetry has been shown to provide improved capability for near-real time decisions in seafloor investigations. [Work supported by ONR and BWB.]
Effects of differing sediment types and structures on normal incident acoustic reflections
Authors: Wood Warren T. , Jans Wolfgang , Smith Eric
Published: July 2002

Data acquired during a recent survey of coastal Florida and the Bahamas have provided an opportunity to correlate normal and near normal incidence acoustic returns with distinguishing seafloor sediment characteristics. These include physical property measurements (both in situ and laboratory) as well as bottom textural measurements derived from diver observations and from video and stereo photography. Measurements were made with a calibrated 1–3 piezocomposite transducer, which offered a very narrow (∼8 deg) beam width over the 10–50-kHz transmitted chirp. In addition, a roll and pitch sensor mounted on the transducer and 0–5 deg ship motion allowed for a monostatic backscatter experiment. This resulted in quatitative measurements of reflectivity versus angle over a relatively broad frequency band. Interestingly, the measured reflection coefficients were significantly lower (especially at high frequencies) and exhibited a greater range in values than those obtained in laboratory tank measurements with a flat, level interface. Also, the range of reflectivity at any fixed angle and anchor location was greater than the systematic dependence on angle. This suggests that very slight ship motion combined with either bottom roughness or discrete scatterers is responsible for the variable reflectivity. [Work supported by ONR.]
Acoustic classification of a shell-covered seafloor
Authors: Stanton Timothy K.
Published: July 2002

Acoustic scattering by the seafloor is sometimes influenced, if not dominated, by the presence of discrete volumetric objects such as shells. Classification of a shell-covered seafloor requires understanding of the acoustic scattering properties of the shells. A series of measurements of target strength of a type of benthic shelled animal and associated scattering modeling have recently been completed. In addition, a simple formula has been derived that expresses the area scattering strength of the seafloor in terms of the reduced target strength (RTS) of the discrete scatterers and their packing factor (where RTS is the target strength normalized by the size of the scatterers). The formula shows that, to first order, the backscattering at high acoustic frequencies by a dense layer of shells (or other discrete bodies such as rocks) depends principally upon material properties of the objects and packing factor, and is independent of size and acoustic frequency. There are reasonable comparisons between scattering data from shell-covered sections of seafloor and predictions using this formula and the measurements/modeling of shell target strength. The functional dependence of this and other seafloor scattering formulas upon shell and shell-bed characteristics are discussed to assess one’s ability to classify a shell-covered seafloor. [Work supported by ONR.]
Relationship of shock wave lithotripsy (SWL)-induced lesion size to renal hemodynamics at differing SWL parameters
Authors: Evan Andrew P. , Willis Lynn R. , Connors Bret A. , Blomgren Philip , Lingeman James E.
Published: July 2002

The present study was designed to determine the relationship between lesion size and hemodynamic changes by altering the kV level, shock number, and pre-treatment status of the kidney. Six-week old pigs were divided into groups based on treatment protocol: 12, 18, and 24 kV at 2000 shocks, 24 kV at 8000 shocks, pyelonephritis 24 kV at 2000 shocks and sham. Following anesthesia each pig was prepared for clearance determinations of glomerular filtration rate, renal plasma flow, and PAH extraction. The lower pole of one kidney was treated with an unmodified HM3 lithotripter except the sham group. Renal function was measured 1 h before and 1 and 4 h after SWL followed by renoval of both kidneys for morphological analysis. Lesion size increased as kV (0.27±0.1%, 2.28±0.3%, 6.1±1.7%, respectively) and shock number (6.1±1.7%, 13.6±1.4%) increased. Renal hemodynamic changes occurred independent of lesion size. Pyelonephritis potentiated the hemodynamic changes seen with 2000 shocks and therefore, more closely mimicked 8000 shocks. Thus two separate mechanisms may be responsible for vascular and tubular injury induced by SWL, and that pre-existing renal disease may potentiate the lesion induced by a clinical dose of SWL. [Work supported by NIH Grant No. PO1 DK43881.]
Use of two pulses to localize and intensify cavitation in lithotripsy
Authors: Sokolov Dahlia L. , Bailey Michael R. , Crum Lawrence A.
Published: July 2002

A single electrohydraulic lithotripter pulse excites a cigar-shaped cavitation field that plays a role in both stone comminution and tissue damage during kidney stone treatment. The diameter and length of such a field (in water) are approximately 1 and 10 cm, respectively, and the lifetime is ∼500 μs. A second, time-delayed pulse can be used to suppress cavitation during growth. As a result, by using two lithotripters facing each other and firing simultaneously, a cavitation field can be created for which the lithotripsy pulses sum coherently at the center to enhance cavitation and counteract each other off-center to suppress cavitation. The result is an intense and localized cavitation field, contained entirely by a cylinder of diameter ∼3 and length ∼4 cm, and having a lifetime twice that of a single-pulse field. When produced in vivo, such a localized cavitation field may increase the rate of stone comminution while mitigating damage to surrounding tissue. Experiments were undertaken in vitro with a Dornier HM3 experimental lithotripter, using a Kodak EktaPro 4540 digital high-speed motion analyzer for data acquisition. [Work supported by NIH PO1 DK43881.]
Clinical trials of a hybrid adaptive beamformer (HAB) for improved speech understanding in noise
Authors: Gibian G. L. , Koroljow Walter , LaRow Andy , Shaw Scott , Nelson Peggy , Sherlock LaGuinn
Published: July 2002

A wearable, hybrid adaptive beamformer (HAB) device has been developed using a four-microphone array and a combination of adaptive and fixed-weight beamforming. The HAB is being evaluated with hard-of-hearing (HoH) listeners in a variety of environments. Pilot tests used HINT test sentences and noise from separate loudspeakers (106-deg angle) in an audiological booth (AI-weighted direct-to-reverberant ratio 9.1 dB). Measured sentence reception thresholds (SRTs) indicated that the HAB provided 14.5, 16.1, and 12.8 dB improvement over the single microphone for two normal-hearing and one HoH listener. Results will be reported for ongoing objective and subjective testing of elderly listeners with mild to moderate hearing losses. Subjects are fitted monaurally with a commercially available behind-the-ear hearing aid with a dual microphone array following the NAL-R fitting algorithm. Comparisons are made between listeners’ SRTs in noise, using: (a) conventional single-microphone, (b) dual microphone, and (c) four-microphone HAB devices. HINT sentences are presented with single and dual noise sources at two arrival angles in three room environments: (a) sound booth, (b) favorable environment, and (c) noisy/reverberant environment. Listeners rate the three hearing aid systems and indicate their preference in paired comparison testing. SRTs, ratings, and preference judgments will be reported. [Work supported by NIH.]
Qualitative and quantitative results from a speech enhancement scheme assessed by hearing-impaired subjects
Authors: Shields P. W. , Campbell D. R.
Published: July 2002

A multi-microphone sub-band adaptive system for binaural preprocessing of speech signals for potential processing in future hearing aids has been investigated. Results are presented from both quantitative and qualitative assessments of the performance of the processing scheme as recorded from hearing-impaired subjects. The quantitative assessment is based on intelligibility testing of the algorithm using real-room recordings, T60=0.3 s, with multi-talker babble as the unwanted noise source. This evaluation has been conducted by using the four-alternative auditory feature test developed by Foster and Haggard [J. Br. Audiol. 21, 165–174 (1987)]. A corresponding mean opinion score on speech quality from each test subject provides the qualitative analysis. A response time measure was included with the qualitative measure. The processing scheme uses the least mean squares (LMS) [S. D. Sterns and R. A. David, Signal Processing Algorithms (Prentice–Hall, Englewood Cliffs, NJ, 1988)] adaptive noise cancellation algorithm in frequency-limited subbands. The inputs from each microphone are split into 16 contiguous subbands using a cochlear distribution according the function provided by Greenwood [J. Acoust. Soc. Am. 87, 2592–2605 (1990)]. Each frequency-limited subband is processed using a LMS adaptive noise cancellation filter operating in an intermittent or continuous mode depending on input signal characteristics. The results show a statistically significant and practically valuable improvement in both intelligibility and perceived speech quality using the proposed scheme.
Headphones as near-field electromagnetic radiators and probable health impairing objects
Authors: Koenig Florian M.
Published: July 2002

The progress in electroacoustics offers a miniaturized, head-related sound source to produce spatial auditory events [F. M. Koenig, AES Preprint No. 4495 (1997)]. These objects, so-called headphones, are working as dynamic (electromagnetic) or electrostatic transducers. Irrespective of this exists knowledge by epidemic studies about low-frequency electromagnetic fields and their health-impairing effects on biological organisms worldwide. A well-known result is the ‘‘TCO (’95) environmental labeling of displays’’ or radiation reduced computer monitors and screens. Independent efforts point out that the TCO idea should be valid also for other electronical consumer products like halogen headlights, clock radios, or housing machines. Is it necessary to add the near-field reinforcing headphone? First measurements over 23 headphones gave the answer, Yes [F. M. Koenig, 24. DAGA (1998), in preparation]. Using a pink noise C-weighted signal by a usual SPL of 70 dB reveals that the majority of customary headphones generate an electromagnetic field emission at the human head, which crosses the border level of the TCO’95 or German recommendation for the housing area [VDE-DIN No. 0848, part 4A1/11/90]. Continued investigations underline this earlier result. The steps’ contrary high-field dispositions will also be shown.
Adjustment factors for assessing long-term aircraft and other noise environments
Authors: Schomer Paul
Published: July 2002

LEQ and DNL are commonly used to assess the long-term noise environments around airports, roads, etc. Frequently, the measure used is the long-term (e.g., yearly average) DNL or long-term daytime LEQ, etc. Schultz and others have related the long-term DNL or LEQ to community response as measured by the percent of a community that is highly annoyed. These relations exhibit a large scatter to the data. It is possible for a specific community to exhibit many times the percent highly annoyed predicted by these ‘‘standard’’ relationships. Some have suggested adjustments to LEQ or DNL to better explain community response and reduce the scatter in the relations between DNL and percent highly annoyed. These adjustments include ‘‘busy day,’’ a ‘‘nave’’ community (not familiar with the sound), a ‘‘quiet rural setting,’’ and the presence of ‘‘rattles.’’ This paper uses experimental data, case histories, and logic, to examine the efficacy of these adjustments.
Military aircraft jet overflights and children’s hearing—Allegations, issues, and measurement uncertainties
Authors: Wheeler Peter D. , Matkovits Nikki
Published: July 2002

The scientific literature of the past 20 years contains several references to the use of high-frequency audiometry for investigating susceptibility to, and early diagnosis of, noise-induced hearing loss. More recently, the measurement of high-frequency hearing acuity in children has been cited as an important tool in the identification and attribution of noise-induced hearing loss from alleged exposure to transient noise sources such as low-flying military jet aircraft. The enormous range of hearing thresholds found above 8 kHz, even in young adults, has been reported by many researchers. Measurement uncertainties in the range 8–16 kHz can be substantial, and detection judgments at such frequencies for inexperienced subjects represent a further source of variance. This study aims to quantify the uncertainties associated with high-frequency audiometric measurements on children and adults in order to inform the interprtation of existing data and assist in the design of new studies. The outcome will be reported and taken into account in a review of the conclusions of recent published work involving high-frequency audiometry for the measurement of children’s hearing in areas subjected to low-altitude military jet overflights.
Motion perception and loudness judgments
Authors: Hellmann Andreas
Published: July 2002

Besides its acoustic properties, many other nonacoustic properties have been shown to influence the judgments of loudness, noisiness, and noise effects of sounding events. In the environment, one finds moving as well as nonmoving sound sources. The sound emitted may be either constant or dynamic. In an experiment, the effect of the perceived motion of a sound source or sound event on loudness judgments was investigated. Sounds were presented which were ambiguous and could be perceived both as moving and as nonmoving events. In different experimental conditions, the same sound stimuli were presented and introduced as moving or nonmoving events. The subjects judged the loudness of the events. At the end of the experiment, it was reported whether they had perceived the sound events as moving, nonmoving, or both. The results show an effect of perceived motion on judged loudness: Loudness judgments are higher if the sound events are perceived as moving than if they are perceived as nonmoving.
An intersensory approach to urban analysis and design
Authors: Couic Marie-Christine , Deletre Jean-Jacques
Published: July 2002

Cresson laboratory’s research on sound in urban space led to the development of a theorical model called ‘‘sonic effect’’ that takes into account not only the physical and space aspects of the sound but also the user’s perception. With this model, some interactions between senses were observed that have been analyzed from an intersensory standpoint. The first step of the method is to register on tape the feeling of candidates when walking through a selected area of the city. This raw material is then analyzed by dedicated software that extracts a few classes where expressions are closed from a semantic standpoint. These classes correspond to specific areas and overlap in transition zones where intersensory perception is expected. Physical measurements (sonic, thermodynamic, luminous) confirm these locations. Further analysis is then performed to reveal dynamic schemes of interaction. The evolution of the relationship between the most salient urban objects and the user is examined in order to consider the evolution between expression (description, evocation,...), motion, and senses. A limited number of protocols was found when meeting an object, but the articulation between the main components of intersensory perception (expression, motion, and senses) is still being analyzed. [Work supported by CNRS/PIR-VILLES.]
Adaptive decision method for acoustical turbomachinery diagnostics
Authors: Bezvesilna Olena N. , Gelman Leonid M.
Published: July 2002

Acoustical turbomachinery diagnostics is advisable to do automatically and complexly using simultaneously different methods. The mentioned diagnostics is condition monitoring diagnostics. Such diagnostics is necessary to do at all operation regimes of turbomachinery and therefore with changes of interfering data of turbomachinery and of environment condition in which diagnostics is carried out. However, in the presence of variable interfering data, optimum properties of decision methods are not realized. In addition, features used for diagnostics are usually statistically dependent. To provide diagnostics in the mentioned conditions it is necessary to apply the adaptive approach. A new automatic adaptive sequential method for acoustical turbomachinery diagnostics is proposed and developed for: (a) presence of variable interfering data; (b) changes in the space of these data limits of erroneous test probabilities; (c) availability of statistical dependencies between features. A new procedure to account for the statistical dependencies between features is proposed and developed. Acoustical diagnostics of the gas-turbine engine based on noise emission is presented. [Work supported by the MacArthur Foundation.]
Application of wavelet decomposition (space-wave number) to sound radiation 1D
Authors: Martinet M. , Hamzaoui N. , Guyader J. L.
Published: July 2002

The purpose of this presentation is to study the contribution of a multiresolution analysis based on a decomposition in wavelets, so as to predict the acoustic radiation of a vibrating structure. In order to analyze the sensitiveness of different parameters of this approach, it is suggested that it be applied to the radiation of a heterogeneous beam in flexion. After an analysis of the radiation associated with different forms of wavelets, the displacement field of the beam is decomposed on a wavelet basis, and its radiation will be then computed and faced with a result stemming from a classical technique. First, the interest, researched by this approach, is linked to the reduction of the number of points of mesh of the vibratory field of the beam, and second, to a physics analysis giving way to access to the spatial localization of the radiated parts. The formulation of the one-dimensional problem, the physics concepts of the multiresolution analysis, and a confrontation with a bibliographic reference, analyzing the advantages and the drawbacks of this approach, are thus presented here.
Using the equivalent sources method (SUP) for multibody radiation problem
Authors: Tomilina Tatiana M.
Published: July 2002

The radiation problem for a finite body vibrating in a fluid near rigid scatterers and for elastic structures is discussed. It is shown that the ESM is the most appropriate method for treating the problem. Formulation of the boundary conditions on the surfaces of elastic scatterers is the key point of the method here. New results of computer simulation and laboratory experiment concerning the energetics of sound radiation are presented. The comparison of two modifications of the ESM is considered in this paper: one modification is based on the Rayleigh multipole expansion and the other uses the equivalent sources of the monopole type.
Numerical modeling of axisymmetric sources in infinite baffle
Authors: Zoltogorski Bronislaw , Dobrucki Andrzej , Szmal Cecylia
Published: July 2002

According to standards, characteristics of loudspeakers should be measured in an anechoic room with the use of sufficiently great rigid baffle. To achieve accordance of numerical calculations to results of measurements, the numerical algorithms for a source in an infinite baffle are needed. In the paper three boundary integral methods—the Huygens–Rayleigh (HR) integral method, the Kirchhoff–Helmholtz (KH) integral method, and the simple-source density (SSD) method—are explored for the sources of revolution with optional surface velocity distributions and shapes of cross sections (cone, flat piston, dome). It was shown that solution of the boundary-value problem for the KH and SSD methods exists and is unique for all frequencies. The HR method is numerically the simplest and is free of existence/uniqueness problems but is theoretically founded for a flat piston only, whereas for sources of other shapes it gives erroneous results. The problem of inclusion of an infinite baffle into the numerical model is easy to overcoming for the SSD method because an auxiliary source-density function rapidly decreases out of source and only a small fragment of the baffle influences the final result. For the KH method that question is more difficult because pressure on the baffle surface does not decrease sufficiently fast. The improved KH method that overcomes this deficiency is described.
Investigation of effective geometrical parameters for a pulse-echo linear array with cylindrically curved, focusing surface
Authors: Wu Ping , Stepinski Tadeusz
Published: July 2002

Linear arrays with cylindrically curved, focusing surfaces working in pulse-echo mode are currently being used for applications in nondestructive testing. Such commercial arrays are usually specified with nominal geometrical parameters (GPs), such as width, length, and radius of curvature (focal length), which, when used in the conventional piston source model, may result in an inaccurate prediction of the actual radiated field. Like a spherical focused transducer which has been extensively investigated for determining its effective GPs, a linear array with cylindrically curved, focusing surface has its effective GPs which allow the piston source model to provide a more realistic prediction of the actual radiated field. The goal of this paper is to investigate effective GPs for such a linear array used in pulse-echo mode. The effective GPs are determined by comparing the fields predicted by the extended angular spectrum approach (ASA), which is applicable to curved transducers, with the measured fields. Pulse-echo fields from the array were measured in water using a pointlike scatterer, and calculated using both nominal and effective GPs in the extended ASA. The results show that effective GPs do permit the piston source model to yield a more precise prediction of the measured fields.
Fiber-optic dielectric multilayer hydrophone for ultrasound detection
Authors: Wilkens Volker , Koch Christian
Published: July 2002

Fiber-tip sensors have proved to be useful for the investigation of ultrasonic signals since they, in principle, overcome some limitations of common piezoelectric hydrophones. A high damage threshold of the sensor is obtained, measurements are not disturbed by electromagnetic influences, and a high temporal and lateral resolution is possible. An optical hydrophone is presented that comprises a fiber tip coated with a dielectric multilayer system of the Fabry–Perot type. The acoustic pressure measurement using the sensor is based on the elastic deformation of the layer system by an incident ultrasonic wave and the detection of the induced change of the optical reflectance. Measurement results obtained by sensors with different layer numbers providing different sensitivities are shown, and the variation of the sensor characteristics depending on the size and shape of the fiber tip is investigated. The appearance of optical loss modulations caused by the stimulation of flexural waves in the fiber in certain measurement configurations is discussed. Several sensor designs are considered to improve the performance of the system in different fields of application, for instance the characterization of lithotripter shock waves, the investigation of cavitation phenomena, and the detection of ultrasound cw signals.
Measurements of near-bed current flow and suspended sediments using acoustics
Authors: Thorne Peter D.
Published: July 2002

In recent years the development of: (i) multifrequency acoustic backscatter systems to measure suspended sediment particle size and concentration, (ii) coherent Doppler and correlation techniques to evaluate flow, and (iii) high-frequency scanning systems to obtain bed microtopography, have significantly advanced the capability to examine the fundamental processes of sediment entrainment and deposition. The outcome from these observations is beginning to make an important contribution to the understanding of the basic mechanisms of sediment transport. In this report, highlights of acoustic measurements of sediment processes collected in both the marine environment and in the laboratory are presented. The particular attribute of acoustics to nonintrusively provide high temporal and spatial resolution profiles of intrawave, and turbulence processes are particularly focused upon, and the scientific output from contemporary studies discussed. [Work supported by the coastal protection division of MAFF through the CAMELOT program, NERC, and the EC contract TRIDISMA, MAS3-CT95-0017.]
Thermal test objects and the measurement of temperature rise produced by diagnostic ultrasound
Authors: Shaw A. , Pay N. M. , Preston R. C.
Published: July 2002

Although the AIUM/NEMA TI (or thermal index) values are now widely used as an indicator of the heating potential of diagnostic ultrasound fields, they are open to criticism on a number of grounds. As an alternative to the TI approach, substantial effort at NPL has gone into developing both reference thermal sensors and tissue mimicking materials for use in thermal test objects (TTOs) to actually measure the temperature rise produced by diagnostic exposure under standardized conditions. In a major project for the UK Department of Health, 20 pulsed Doppler fields have been measured with both soft tissue and soft tissue/bone TTOs under worst case and AIUM-equivalent derated conditions. Results were compared with calculated TIs, with NPL predictions of temperature rise and, when available, with the scanner’s on-screen TI value. Under worst case conditions, up to 3°C was measured in soft tissue mimic and up to 10°C in bone mimic; AIUM-equivalent measurements were generally three to five times lower. Calculated TI values were generally intermediate between AIUM-equivalent and worst case values. This presentation will briefly describe the design and performance of the TTOs and discuss the comparison with other methods and the significance of the findings.