bluuebunny/crossref_metadata_2025 huggingface dataset:
Applications of virtual auditory space in psychoacoustics and neurophysiology
Authors: Hartung Klaus , Sterbing Susanne J. , Keller Clifford H. , Takahashi Terry T.
Published: July 2002

Virtual auditory space (VAS) refers to a technology where the source signal is convolved with filters called head-related transfer functions (HRTFs) and presented over headphones to recreate the signal at the eardrum that would have been received from a source in the free-field. VAS is a powerful tool because it allows the simulation of complex and realistic scenarios (e.g., echoes, reverberation, moving sources) that are impossible or too complicated for free-field setups, which often contain distortions caused by the setup itself (e.g., stereotactic bench, headholder). Crucial points of VAS are the measurement, equalization and interpolation of the HRTF. Different methods will be reviewed and the results of VAS and free-field stimulation for humans, guinea pigs, and barn owls will be compared. For barn owls, the amplitude spectra of virtual sounds were within ±1 dB of amplitude spectra of free-field sounds measured near the eardrum. The neuronal responses to free-field and VAS presentations were nearly indistinguishable. For research with humans and guinea pigs, it was necessary to use the HRTF of each individual, whereas in the barn owl, only minor differences between the neuronal responses to the individual and nonindividual HRTF were observed. [Work supported by DFG, NIDCD, and NATO.]
Measurement of 3-D scattering from buried targets in very shallow water
Authors: Schmidt Henrik , Maguer Alain , Bovio Edoardo , Fox Warren
Published: July 2002

The objective of the GOATS’98 experiment was to determine the three-dimensional, spatial characteristics of seabed target scattering and reverberation in coastal environments with water depth less than 15 m. The experiment was carried out at Marciana Marina, Elba Island, in May 1998 in a joint effort between SACLANTCEN and MIT. Artificial targets were buried at various depths into the sandy bottom and insonified by a parametric source mounted on a 10-m tall tower which could be repositioned on a bottom-mounted rail under remote control. This arrangement allowed for insonifying the targets at a wide range of incident angles, including both the sub- and supercritical regimes. The scattering and reverberation were measured using a suite of fixed and mobile arrays. Specifically, an eight-element line array was mounted on an MIT Odyssey-II autonomous underwater vehicle (AUV) in a ‘‘swordfish’’ configuration. The AUV was launched from R/V Alliance, anchored off-shore, to perform survey patterns in the target area, way-point navigated using a long baseline acoustic navigation network. During these surveys the parametric source would insonify the seabed at a high repetition rate, allowing for dense mapping of the 3-D scattering and reverberation. This paper reviews the experiment and the results, with particular emphasis on the versatility of using the new AUV technology for shallow-water target scattering measurements.
Target classification in shallow waters by time-frequency filtering
Authors: Gache Nicole , Chevret Patrick
Published: July 2002

Efficient sonar target recognition must be based on a set of relevant parameters extracted from the echoes and directly related to the geometrical and mechanical properties of the target. Previous studies have shown that a wideband approach based either on simple spectral modeling or on time-frequency analysis is particularly suited to the understanding of echo formation mechanisms and to the classification in the free field (recognition rate as high as 96%). In shallow waters, the influence of the boundaries considerably reduces the performance of these methods due to the presence of several spurious echoes superimposed to the target echo components. Classification performance can be improved by using a method based on time-frequency filtering matched to a free-field reference target response. This method will be described and applied to experimental data issued from tank experiments. Several typical configurations have been first investigated: free-field, semi-infinite space for a set of targets (shells and solid targets of different shapes). It gives more than encouraging results, especially for the recognition of a spherical shell (about 100% of recognition). The method is now extended to a shallow-water configuration including seabed interaction.
Numerical simulation of transient scattering from bodies and shells in a layered fluid–solid medium
Authors: Karasalo Ilkka , Mattsson Johan
Published: July 2002

Results from numerical simulation of transient scattering by 3-D objects immersed in seawater or buried in the bottom sediment are presented, and compared with data from a shallow-water experiment in the Baltic in which a bottom-penetrating parametric sonar was used for detection of submerged or buried objects. A range-independent fluid–solid model of the medium is used. The scatterers have smooth shape and are modeled as acoustically impenetrable or alternatively penetrable fluid-enclosed thin elastic shells. The dynamics of such shell-structured scatterers are described by Love’s equations for thin shells. A recently developed numerical technique, based on a frequency-domain boundary integral equation (BIE) formulation of the scattering problem, is used to compute the scattered field. The Green’s function of the layered medium is obtained by an adaptive transform integral method. The BIE is discretized by high-order B-splines, point collocation, and global numerical quadrature. The incident field may be excited by a point source, a point source array, or a plane wave. Scattering of transient fields is computed by Fourier synthesis of monofrequent field components. The composite simulation being highly parallelizable, a version for execution on workstation clusters under MPICH has been implemented, allowing for convenient handling of also computationally demanding broadband excitations.
Measurement of K
ij with free-standing masonry walls
Authors: Hopkins Carl P.
Published: July 2002

Measurements have been carried out to determine Kij values for masonry blockwork wall elements in the laboratory. Structural coupling measurements in the laboratory required investigation of the energy flow on the test construction in conjunction with the laboratory as well as determination of the coupling/material parameters. Experimental work was carried out on full-size masonry wall elements that were free-standing upon a concrete floor base. Measurement procedures used to determine Kij were based upon proposals made by CEN/TC126/WG6. The intended use of the measurements was to investigate structural coupling between masonry walls for the generic T-junction with two different junction connection details, interleaved blocks and butted and tied blockwork. To compare the two different types of junction connection, an H-block construction was used that consisted of a single separating wall element with four flanking elements. When the modal overlap determined from measurements was less than unity, the general trend was that the laboratory measurements overestimated Kij in comparison to values quoted in prEN12354-1.
Vibration response of building elements in wood frame constructions when excited along an edge
Authors: Nightingale T. R. T. , Halliwell R. E.
Published: July 2002

When predicting the apparent sound insulation in wood frame buildings it is necessary to obtain accurate measures of both the junction attenuation and any attenuation of the structure-borne sound in the surfaces connected to the junction. Most walls and floors in wood frame constructions can be viewed as being rib-stiffened plates and as such they can not be treated as homogeneous and isotropic. The framing members, joists in the floor and studs in the wall, may break the surface into a series of smaller subpanels. Measured velocity data are presented to show that if structure-borne energy is propagating at right angles to the framing members, then the vibration response of the surface will not be uniform and there will be a strong gradient in the energy density. More energy is stored near the source. It is also shown that a gradient exists for the case where the direction of propagation is parallel to the framing members. In both cases internal losses are insufficient to account for the gradient. This has several important implications, as it may bias measures of junction attenuation and framed surfaces may have to receive special treatment in prediction models. These issues will also be discussed.
Vertical flanking sound transmission loss by timber-framed-glass facades
Authors: Schumacher Rolf , Sass Bernd
Published: July 2002

The results of measurements both of the airborne and the structure-borne flanking sound transmission by timber-framed-glass facades are reported following the new European drafts standards for flanking transmission of lightweight partitions in the laboratory [document of CEN/TC 126-N 284...286 (1989)]. Several practical types of junctions of these facades to a massive concrete wall/ceiling have been investigated by airborne and structure-borne excitation to discuss the question, if this junction resp. the vibration reduction index Kij has a substantial influence on the transmission loss of the junction or not. The results, especially by using the vibrational excitation method, show effects of a structural absorption decrease along the length of the element, the differences in the structural reverberation time Ts due to the different materials of the single elements of the facade, and the description of the overall transmission loss as an additional combination of the detailed parts of the element. Comparison with the mathematical model of overall sound transmission between adjoining rooms in a building due to prEN 12354-1:1996 with and without junction loss will be discussed. [Work supported by DGfH and NABau.]
Prediction equations of isolating systems: Gypsum panels
Authors: Recuero Manuel , Gil Constantino , Minguez Antonio Antonio
Published: July 2002

Several prediction equations of acoustic noise isolation are presented and applied to gypsum structures of one, two, and three plates, with different thickness. On the other hand, acoustic noise isolation for simple, double, and triple gypsum panels is measured in transmission loss chambers officially recognized. The experimental results obtained are compared with the values obtained with the prediction equations in order to evaluate the error. The measurements are done in 1/3-octave bands as the ISO 140-3 proposes, using B&K equipment. It has also measured the panel vibrations with accelerometers with acoustic intensity techniques in order to explain several panel behaviors. Taking into account the former results, some prediction equations have been obtained versus mass and frequency, for values below 50 kg/m2 so the measuring process can be done easily.
Sub-band imaging and mapping for seabed characterization using a wideband synthetic aperture bathymetry prototype
Authors: Chatillon Jacques
Published: July 2002

Seabed was surveyed by means of two side-scan arrays. Echo processing was based on synthetic aperture technique and cross correlation for providing high-resolution maps. The paper deals with some results obtained by means of this sonar with several processing techniques. The use of synthetic aperture processing leads to sonar images with a constant resolution; the bathymetry processing permits the retrieval of the elevation of the resolution cells in order to reconstruct the relief of the seabed. The use of wide band signals (6–12 kHz) has allowed the development of time-domain algorithms for processing high-resolution images and maps. Additional information on the seabed was extracted from the spectral signatures of the echoes. First, splitting the global bandwidth into several sub-bands permitted the evaluation of the sound penetration into the sediment. This led to several images of the same area with additional spectral information. Second, the bathymetry was used in order to compensate the influence of the grazing angle on the echo spectrum. This processing gives the spectral coloration of the bottom echoes directly, and leads to an efficient method for seabed characterization and classification.
Wavelet imaging of temporomandibular joint in motion for real-time diagnosing system
Authors: Lis Waldemar , Moszynski Marek , Salamon Roman
Published: July 2002

The new inexpensive method of diagnosing the temporomandibular joint by analyzing acoustic emission signals generated by the joint in motion was presented previously [W. Lis et al., ‘‘Application of processed acoustic emission data for investigation of temporomandibular joint pathology,’’ Proc. of 47th ICB Seminar on Ultrasound in Biomeasurements, Diagnostics and Therapy (1998)]. Moreover, the advantages of wavelet techniques over classical Fourier analysis were observed for this case. The time-frequency imaging of such signals has clear anatomic interpretation of pathological diseases. The paper presents the adaptation of discrete wavelet transform (DWT) for analysis of signals acquired from the temporomandibular joint in a real-time system. Additionally, it is shown that common PC hardware is sufficient for collecting data and real-time display. Specially designed software for acquisition and analysis of acoustic emission of this joint was developed and results of its use are presented. The software package was equipped in small database for managing the measurements of clinical cases.
Speech and hearing demonstrations in m
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Authors: Cooke Martin P. , Brown Guy J.
Published: July 2002

Education can be greatly enhanced by the provision of tools which allow students to interact with, explore, and manipulate key elements of the phenomena under study. Such facilities are even more important in areas such as the perception, production, and recognition of sounds, whose subject matter is difficult to convey by words or pictures alone. Consequently, a collection of software applications has been developed, each adopting either an ‘‘experiment-replication’’ or a ‘‘white box’’ paradigm. The first category includes demonstrations of audiometric testing, perceptual separation of concurrent vowels, perception of alternating two-tone stimuli, and auditory induction. In the ‘‘white box’’ paradigm, students interact with the parameters of an algorithm or model, such as endpoint detection of speech, cepstral analysis, and models of peripheral auditory function. The applications are written in matlab, which provides a high-level interface to signal processing tools, graphical user interface components, and sound handling functions. As part of an ongoing action research study, the value of this work is being assessed against our learning objectives for final-year undergraduate and masters-level courses in speech and hearing technology. [Work supported by EU ELSNET Language Engineering Training Showcase.]
Mechanical response of artificial buzzing lips
Authors: Cullen John S. , Gilbert Jöel , Campbell D. Murray
Published: July 2002

Brass instruments sound when the coupling between the acoustical resonator (the instrument) and the mechanical oscillator (the lips) results in a self sustained oscillation. It is the aim of this investigation to characterize experimentally the mechanical response of the lips and to examine its influence on the lip motion observed under near-threshold playing conditions. In this investigation artificial latex rubber lips replace the lips of a human player. Particular emphasis is placed on studying the development of the mechanical response as the embouchure is tightened or as airflow through the lips is introduced. The effect of the acoustical coupling provided by the mouthpiece is investigated. Also presented are playing test measurements, carried out at a level just above the threshold of oscillation. The artificial lips are used to excite resonators of various acoustical lengths; for each resonator the relation of the playing frequency to the nearest lip and resonator resonance frequencies is examined and the measured phase difference between lip opening area and mouthpiece pressure is compared with the phase angles of lip mechanical response and resonator input impedance at the playing frequency. The observed oscillation threshold behavior is compared with that predicted by theoretical physical models.
Joint noise annoyance: A field evaluation of models concerning road and railway exposure
Authors: Lercher Peter , Widmann Ulrich
Published: July 2002

There is still controversy about how to deal appropriately with a noise exposure situation where two noise sources are of equal importance to an exposed population. Reanalyzing an older German study [Planungsbro Obermeyer (1983)] Ronnebaum et al. (1996) have shown that in a situation where no source is dominant and both sources produce more than 53 dB, Leq, overall annoyance is less than annoyance of the most annoying source. In an ongoing large-noise survey (N=2000) in the Austrian part of the Alps (TYROL) legal requirements force noise ingenieurs to use simple energy summation models in the absence of state of the art alternatives. Selected models [Flindell (1983), DELTA Acoustic & Vibration (1995)] are evaluated in a complex topographical situation (narrow valley with residential areas on the slopes) where noise annoyance due to railway noise has increased over the last decade in spite of a constant number of train passages. The results of this evaluation will be reported and discussed in terms of its usefulness for environmental risk assessments.
Social survey of the annoyance of low-frequency aircraft ground noise
Authors: Fidell S. , Silvati L. , Lind S. , Pearsons K.
Published: July 2002

Concerns about the appropriateness of representing low-frequency aircraft ground and near-ground noise in A-weighted units, and about the adequacy of standard interpretive criteria for assessing community response to low-frequency noises, are becoming more common at large civil airports. Residents of a neighborhood adjacent to a busy runway were interviewed to determine the annoyance of runway sideline noise at frequencies below 100 Hz, and of its audible manifestations inside homes. Extensive measurements were made to estimate low-frequency noise contours in the interviewing area, and street addresses of respondents were geo-coded to permit assignment of low-frequency noise levels to each household. Residents who were highly annoyed by low-frequency sideline noise were concentrated in areas with maximum sound levels summed in one-third octave bands between 25 and 80 Hz (inclusive) that were in excess of 75–80 dB. These levels are consistent with Hubbard’s (1980) estimates of low-frequency airborne sound levels capable of inducing secondary emissions in light architectural elements of residences.
Hearing conservation for workers in British Columbia and Canada
Authors: Harrison Christine
Published: July 2002

Comprehensive hearing conservation programs for noise-exposed workers in British Columbia have existed since 1978. From 1978 to 1996, a program consisted of engineered noise controls, hearing protection use, and annual hearing tests. In 1996 more statutory components were added: exposure monitoring of workers, posting of noisy work areas, education and training, and annual review of the program. Several administrative aspects of the province-wide program are unique; for example, all hearing tests are recorded on a single, standardized computer form and submitted to the central data base of the Workers’ Compensation Board. Industries which have submitted hearing tests include forestry, construction, and manufacturing. The construction program itself is unique in a number of aspects. As of 1998, well over one million audiometric records (each of which includes information regarding occupation, years of noise exposure, threshold values, hearing protection use, nonoccupational noise exposure, age, gender, and more) are in the data base. Analysis of this data has only begun, but interesting trends have been identified. These trends will be presented, with a discussion of methods of program evaluation, as well as an overview of hearing conservation practices across Canada.
Assessment of hearing conservation program implemented in chosen plants in Poland
Authors: Pawlas Krystyna
Published: July 2002

In Poland, as in other industrialized countries, noise is a serious problem of occupational medicine. On the basis of the Polish state law, managers of noisy plants are obliged to implement the hearing conservation program. The program consists of noise measurement, noise reduction by technical means, periodical hearing examination of workers exposed to noise, use of hearing protectors, and training of workers. Nevertheless, 30% of all new cases of occupational diseases recognized every year in Poland are the noise-induced hearing loss (NIHL). Most cases of NIHL are recognized in the mining and metallurgical industries. One of the projects previously carried out analyzed the efficiency of medical prophylaxis [J. Grzesik and K. Pawlas, Ochrona Zdrowia Publicznego 96, 516–523 (1985), in Polish]. Hearing conservation programs performed in chosen plants (mines and foundries) were evaluated. Each point of the hearing conservation program was investigated on the basis of the data collected in the plants. Hearing protector devices used by workers were examined, too. The researchers discovered weak points in the activities of health services and occupational hygiene departments as well as of managers and workers.
Assessment of methods for determining field-equivalent sound levels from real-ear and manikin measurements
Authors: Hammershoei Dorte , Moller Henrik
Published: July 2002

The usual method of measuring noise with a sound-level meter at the position of the exposed person, but with the person absent, is not applicable for sound sources placed close to the ears. For measurement of the noise emission from such sources, the coupling between the sound source and the ear must be similar to that of the real life situation. This can be achieved by using the microphone in real ear technique (the MIRE technique) or the manikin technique as described in the upcoming ISO 11904, parts 1 and 2, respectively. For evaluation and comparison with traditional criteria, the measured ear or manikin sound-pressure levels are subsequently converted into either free-field or diffuse-field equivalent sound-pressure levels. The uncertainty of the final result depends on the method used. For the MIRE technique, the uncertainty is mainly related to the statistical uncertainty as determined by the variation between humans and the number of subjects used. For the manikin technique, the uncertainty is mainly related to the deviation of the manikin’s acoustical characteristics from those of humans. The paper presents an overview of the methods and examples of practical results.
A pistonless Stirling engine—A new direction in thermoacoustics
Authors: Backhaus Scott N. , Swift Gregory W.
Published: July 2002

Due to its thermodynamic reversibility, the Stirling cycle has an inherent advantage in thermal efficiency over the standard, irreversible standing-wave thermoacoustic cycle. The main disadvantage of the Stirling cycle has been the need for high-pressure, sliding piston seals. Building significantly on the ideas of Ceperley [J. Acoust. Soc. Am. 66, 1508 (1979)], a thermoacoustic version of a 1-kW Stirling engine has been constructed and tested. This engine enjoys both the efficiency advantage of the Stirling cycle and the no-moving-parts advantage of thermoacoustics. In this first attempt, experimental data show that the engine has an efficiency above 35% of the Carnot efficiency, much higher than that of any prior thermoacoustic engine. [Work supported by the Office of Basic Energy Sciences in the U.S. DOE.]
Measurements of thermoacoustic functions for unusual stacks
Authors: Petculescu Gabriela , Wilen Larry A.
Published: July 2002

Following earlier work [G. Petculescu and L. A. Wilen, J. Acoust. Soc. Am. 103, 2841(A) (1998)], a volume-modulation technique is employed to measure directly the complex compressibility of gas in a stack. When a temperature gradient is imposed on the stack, the complex compressibility is sensitive to thermoacoustic effects which can be measured to high precision. These effects depend on both thermal and viscous properties of the gas. Direct measurements of the thermoviscous functions analogous to F(λ) and F(λT) will be presented for unusual geometry stacks, such as conical shapes or stacks constructed from reticulated vitreous carbon (RVC). The behavior of a stack with a sharp temperature gradient approximating a temperature discontinuity will also be described. Time permitting, nonlinear effects may also be discussed. [Work supported by the Office of Naval Research and Ohio University Research and Sponsored Programs.]
Architecture and music: A laboratory
Authors: Dutilleux Pierre , Müller-Tomfelde Christian
Published: July 2002

A museum exhibit gives the visitors an opportunity to experience the relation between sounds and performance space. A catalog of dry recorded sounds is available, as well as two categories of performance spaces: The so-called complex shapes (i.e., concert hall, roman theater, living room, natural echo) and the so-called basic shapes (i.e., free field, tube, cube, sphere). The visitor is free to combine any sound with any space. A computer processes the sounds as if they were heard in the selected space. The impulse responses of the complex shapes have been measured and a room simulator (Spatialisateur) has been programmed to imitate these spaces. The basic shapes are imitated using simpler algorithms. The resonances of the sphere are distributed according to the roots of the first derivative of the Bessel functions. The room selection is such that most people can recognize or identify a space after listening to a few sounds. Visitors, musicians, and even acousticians can learn intuitively how a piece of music sounds in one place or in another. Music students are fascinated to hear how a room can modify the sound of their instrument. The basic shapes allow the demonstration of modal acoustics.
Some aspects on fairly objective results of subjective tests
Authors: Wogram Klaus
Published: July 2002

When performing tests with playing subjects on musical instruments it is neccessary to regard that the musicians judge under the influence of prejudices and the appearence of the instrument under test. This obviously affects the results which are no longer generally accepted. To avoid those difficulties the PTB has developed a method which delivers mostly reproducible results for the compared instruments. The aim of this method is to create a psychological situation in which the subject is no longer interested to identify the manufactor and the type or model of the specimen, but will concentrate strictly on the musical parameters like tone color, response, intonation, and others.
On the effect of phase relations for the perception of pitch and timbre of bass tones
Authors: Galembo Alexander , Askenfelt Anders , Cuddy Lola L.
Published: July 2002

In contrast to the old classic statement that the human ear is insensitive to phase relations, many results have been published by psychoacousticians that demonstrate the influence of phase on timbre and pitch perception in experimental situations. The experiments usually involve artificial complex tones consisting of high order (unresolvable) harmonics restricted to a specific region of fundamental frequencies. A musically important question is whether or not the effects of phase on pitch and timbre perception are sufficiently strong to be relevant to discussions of the tone quality of real musical instruments. Acoustical analyses and tests of perception in the bass range, where temporal processes are thought to be prominent, provide promising means of studying such effects. Experiments with phase relations in bass tones will be presented. The examples range from harmonic steady multicomponent tones with flat spectrum to inharmonic tones with pianolike spectral dynamics. The results presented have implications for psychoacoustical demonstrations and for a batter understanding of the tone quality of musical instruments, in particular the piano.
Methods of determination of acoustic data in field studies
Authors: Liepert Manfred , Moehler Ulrich , Schuemer Rudolf , Griefahn Barbara
Published: July 2002

An interdisciplinary field study examining the annoyance by rail and road traffic noise with special regard to sleep disturbance was carried out. The noise induced responses were determined by questionnaires and physiological measurement of sleep disturbance. For subjects taking part in the physiological examination, acoustical measurements have been taken inside and outside the bedroom. The individual noise levels for all subjects have been calculated using the German standards RLS90 and Schall03. As input variables (such as number and speed of passing trains or vehicles) for these calculations on one hand measured data and on the other hand official data have been used. Whereas the measured data deliver reliable information about the traffic during the physiological measurements, the official data mostly refer to maximum (e.g., speed) or average values. Furthermore, the noise levels have been calculated for different measurement points. Thus, together with the measured noise levels a variety of subject individual level values have been collected. The selection of these noise levels and the effect on the noise response relationship shall be discussed. Special regard will be taken on indoor and outdoor levels and the aspects of measurement and calculation and its input data.
Strategy for locating the reference sound source and microphones when determining sound power in situ. A theoretical investigation for the revision of ISO 3747
Authors: Jacques Jean R.
Published: July 2002

A present challenge in industrial acoustics is the accurate determination of the sound power of large machines in ordinary workrooms. Such a method is being worked out as the revised ISO 3747 standard. It is a comparison method with sound pressure measurements at a limited number of microphone positions in the reverberant field. The accuracy of the method was studied using a high-performance ray-tracing computer model for the propagation of sound in industrial halls. All parameters influencing the accuracy of the method have been considered: room size and wall absorption, dimensions and shape of the machine, source distribution (one single point source or a distribution of point sources over the machine volume), omnidirectional and directional machines, position of the reference sound source with respect to the machine (on top or to the side), and microphone positions. Results analysis shows that sound power can be determined with grade 2 of accuracy even for large directional machines operating in moderately reverberant workrooms provided a specific methodology is used for locating the reference sound source and the microphones based on a zoning of the room. A criterion for validating a microphone position based on the excess of sound pressure level is proposed.
Noise as indicator of instability in centrifugal pumps
Authors: Čudina Mirko
Published: July 2002

The total emitted noise from the pumping set is generated partially by the pump, partially by the electric motor and partially by the cooling fan, and has four characteristic noise origins: aerodynamic, hydrodynamic, mechanical, and electromagnetic. Emitted noise level of a centrifugal pump depends on its size and the operating conditions (speed and load). At the design point of operation (Qdes) and without cavitation the hydrodynamical and aerodynamical noise in form of the rotational noise due to the rotational frequency and blade passing frequency are predominant noise sources. At the off-design operating condition the dominant noise sources within the pumping set without cavitation of the pump is nonrotational noise due to the rotating stall and surge, at QQdes. When the cavitation within the pump occurs the nonrotational noise predominates within the entire range of operating conditions. The onset of the stall, surge, and cavitation in the centrifugal pump cause instability of a pumping system. Special attention was given to the state of pump operation when the instability due to the stall or surge and cavitation simultaneously occurs, and to the noise generated thereof.
Effects of absorptivity due to fish on transmission loss in shallow water
Authors: Diachok Orest
Published: July 2002

Absorption losses at the resonance frequencies of sardines, 1.3 kHz (18 dB) at night, 1.7 kHz (15 dB) during the day and 2.7 kHz (35 dB) at dawn, were observed at a range of 12 km at a shallow water site in the Gulf of Lion in September of 1995. These observations were made during Modal Lion, a multidisciplinary experiment, which was designed to isolate absorptivity due to fish from other effects on long range propagation. Systematic changes in the resonance frequency of dispersed sardines were consistent with concurrent echo sounder observations of the vertical migration of sardines at twilight. Comparison of transmission loss measurements with a numerical sound propagation model that incorporates absorption layers in the water column permitted estimation of the average absorption coefficient, depth and thickness of absorption layers. Depths and thickness of layers estimated from sound propagation measurements were in good agreement with echo sounder data. Measured resonance frequencies, f0, of dispersed fish were in good agreement with theoretical computations based on measured swim bladder dimensions. The measured resonance frequency of sardines in schools, which were at a depth of about 65 m, was about 0.6 times the resonance frequency of dispersed sardines. The observed frequency shift is consistent with an analytical equation of the fundamental resonance frequency of a “cloud” of bubbles, an average separation between fish in schools of about 0.8 fish lengths and 5×103 fish per school. These estimates are consistent with previously published estimates of these parameters. The resonance frequencies of other absorption lines are consistent with the hypothesis that absorptivity due to sardines generally manifests itself in pairs of absorption lines, which correspond to the resonance frequencies of an ensemble of individual sardines, and the resonance frequencies of an ensemble of schools. Matching of theoretical calculations with inferences of the absorption coefficient permitted estimation of the average number of dispersed sardines per unit volume, which also consistent with previously published estimates. The results presented here suggest the possibility of long term tomographic mapping of fish parameters over large areas using broadband transmission loss measurements.
Diffraction of an acoustic plane wave by a rectangular hole in an infinitely large rigid screen
Authors: Hongo Kohei , Serizawa Hirohide
Published: July 2002

The method of the Kobayashi potential (KP) is applied to evaluate an acoustic field diffracted by a rectangular hole in an infinite rigid screen. The screen thickness is assumed to be negligibly small. The KP method yields an eigenfunction expansion of the present geometry, and the expansion coefficients are obtained from the matrix equation. The intensity pattern of the far diffracted field, the velocity distribution on the hole, and the transmission coefficient are numerically evaluated. The intensity pattern results are compared with those obtained from the Kirchhoff’s diffraction integral. The agreement between them is fairly good. Since no existing method has provided transmission coefficients for a rectangular hole in a rigid screen, these results are compared with the total scattering cross section of the soft disk, which is analogous to a circular hole in a rigid screen. Their frequency characteristics are found to show a similar variation.
Three-dimensional transducer voltage in anisotropic materials characterization
Authors: Lobkis Oleg I. , Chimenti D. E.
Published: July 2002

Air- and fluid-coupled ultrasound has been used to characterize experimentally the elastic behavior of composite materials by employing a 3-D voltage calculation to model transmission or reflection experiments. With sound propagation along material symmetry directions, integration over the incident-plane angle alone is generally sufficient to model the transducer voltage accurately, where a saddle-point calculation is used to evaluate the dependence of the diffraction integral on the out-of-incident-plane angle φ. In general material directions, however, this integration must be extended to account for φ-dependent variations in the reflection or transmission coefficient that give the scattering a strong, asymmetrical dependence on φ. This article presents theoretical and experimental results to illustrate this effect and explores the relationship between the 2-D and 3-D calculations. Experimental results demonstrating viscoelastic property reconstruction in composite plates in both air-coupled and liquid-coupled measurements are presented. It is shown that the influence of the φ-dependent integration on the voltage, embodied in the 3-D calculation, is particularly strong when the incident angles are small and the wave paths are large, as typically experienced in air-coupled measurements.
Robust broadband matched-field localization: Results for a short, sparse vertical array
Authors: Harrison Brian F. , Vaccaro Richard J. , Tufts Donald W.
Published: July 2002

Matched-field localization is typically applied to signals received by long vertical arrays. A much more challenging problem is the application of these techniques to short vertical arrays. Short arrays require the use of multiple frequencies in localization processing to reduce ambiguities. In addition, any practical localization algorithm must also be robust to environmental uncertainties. In this paper, the results of applying the robust multiple uncertainty, replica-subspace weighted projections (MU-RSWP) localization algorithm to the broadband signal/short-array problem are presented. Simulation results for two uncertain shallow-water environments are given using a short five-element array which demonstrate the significant performance improvement in using MU-RSWP over the Bartlett processor. These results serve as an illustration of the applicability of using short arrays, in conjunction with a robust localization algorithm, for matched-field localization in realistic environmental scenarios.
Vocalizations in two captive born Florida manatees (Trichechus manatus latirostris)
Authors: Frisch Katherine J.
Published: July 2002

Florida manatees (Trichechus manatus latirostris) are an endangered species with a population of less than 3000 individuals. They are known to produce sounds. Some attempts have been made to characterize their vocal repetoire. However, little has been documented about intermanatee differences in these vocalizations. This pilot study was undertaken to examine the acoustic differences in vocalizations of two captive born manatees at Mote Marine Laboratory in Sarasota, FL. The manatees were recorded at random intervals while engaged in typical activities. The recordings were analyzed along a number of dimensions. Despite a great deal of overall variability, there was a clear bimodal distribution of frequency characteristics, particularly near the end of the vocalization. This suggests that manatee vocalizations may have an individually determined natural frequency range. These acoustic cues could provide additional means of identifying and distinguishing individuals from each other in the wild. Such a finding has important applications, for example, in the effort to preserve the species as an aid in the cataloging of individual animals.
The influence of African musical traditions on gospel music
Authors: McCrary Jan , Wise Raymond
Published: July 2002

The paper examines historical and cultural influences of African music traditions on African–American gospel and spiritual music. Gospel music is one of several African–American genres of sacred music developed during the 1920’s and 30’s when musicians combined elements of blues and jazz music with church hymns and spirituals. The paper examines scholarly investigations of the impact of African music traditions on the development of gospel and spiritual music in America. In addition, the paper will explore unique African and American cultural influences on specific vocal-style characteristics. The session will feature The Ohio State University African American Music Chorale, which will perform representative short examples of African–American gospel and spirituals. The chorale also will present a short concert of complete works immediately following the session.
Analysis of impact noise of nail ejection in wire nail machines
Authors: Ding Jack , Al-Jumaily Ahmed , Wilson Doug
Published: July 2002

A wire nail production machine can be classified as one of the punch press machines. By nature, the production of wire nails involves the development of a series of force impulses, which in turn generate various sound pressure levels with different frequencies. Typically, the machine operations generating impact noise include pressing, cutting, ejecting, wire gripping and feeding. The punch pressing is the movement of punch header to press forming the nail head. It produces a large force impulse, which in turn generates a high level of impact noise and consequently high levels of ancillary impact noise such as the impact noise by the backlashes. It has been found that this type of impact noise is not necessarily the most annoying one. The impact noise generated by nail ejection, however, has been identified as one of the annoying noise components. The ejector used in a nail machine for executing the movement of nail ejection produces ringing noise at high frequencies when it is struck by the punch header in each cycle of the machine operations. This paper presents the analyses of and experiments on the ejection force impulse and the characteristics of the impact noise generated by nail ejection.
Hot jet noise computed using large eddy simulation, computation of compressible free jet turbulence
Authors: Schein David B. , Meecham William
Published: July 2002

A computational fluid dynamics model for free, heated jet flow and resultant far-field sound has been developed which uses large-eddy simulation (LES) and Lighthill’s acoustic analogy. A deductive, subgrid scale model (based on a Taylor series expansion of the weighting function in the Favr E9 expansion) is used for the turbulent simulation. The simulation has been tested using published experimental mean flow field and rms fluctuation data [W. R. Quinn and J. Militzer, Phys. Fluids 31 (1988)] for a turbulent, free, square jet (known to be the same as a round jet of the same area). The ultimate objective is to address large Reynolds number, high subsonic (compressible) flow with realistic geometries, more representative of aircraft engine exhausts than can be considered using direct numerical simulation (DNS). In the simulation, Gaussian random velocity fields are introduced at the jet exit to excite the turbulence. The far-field sound and directivity is computed using the time-derivative form of Lighthill’s source-integral result (formulated in terms of quadruple sources from the simulated flow field), which is integrated in time and contains the fluctuations set up by the time-varying stress tensor. Simulation for a WR 19-4 turbofan engine exhaust (Re-2×106 based on exit velocity and diameter) was performed, and propagated jet noise results compared with experimental acoustics data.
Problems of signal processing in modern wireless terminals and its impact on speech quality
Authors: Diedrich Ekkehard , Gierlich Hans Wilhelm
Published: July 2002

Modern terminal applications in speech communications are more and more including signal-processing technologies, such as switching devices, echo cancellers, nonlinear processors, level control, and compander a.o. Apart from the benefits of such technologies, there are doubtless impacts on the speech transmission quality like echo, level fluctuations, and clipping. Even modern terminal developments, e.g., for mobile communications lead to shorter and compact handset designs with some negative influences on the speech transmission quality from an acoustical point of view. One example is echo because of the stronger internal coupling between microphone and loudspeaker in very short handsets and the need for echo control to avoid the negative impact on speech quality. New test and measurement procedures (subjective and objective) are described and discussed to give the possibility of classifying these impacts on speech transmission quality.
Cortical, auditory, evoked potentials in response to changes of spectrum and amplitude
Authors: Martin Brett A. , Boothroyd Arthur
Published: July 2002

The acoustic change complex (ACC) is a scalp-recorded negative–positive voltage swing elicited by a change during an otherwise steady-state sound. The ACC was obtained from eight adults in response to changes of amplitude and/or spectral envelope at the temporal center of a three-formant synthetic vowel lasting 800 ms. In the absence of spectral change, the group mean waveforms showed a clear ACC to amplitude increments of 2 dB or more and decrements of 3 dB or more. In the presence of a change of second formant frequency (from perceived /u/ to perceived /i/), amplitude increments increased the magnitude of the ACC but amplitude decrements had little or no effect. The fact that the just detectable amplitude change is close to the psychoacoustic limits of the auditory system augurs well for the clinical application of the ACC. The failure to find a condition under which the spectrally elicited ACC is diminished by a small change of amplitude supports the conclusion that the observed ACC to a change of spectral envelope reflects some aspect of cortical frequency coding. Taken together, these findings support the potential value of the ACC as an objective index of auditory discrimination capacity.
Community reaction to aircraft noise: Time-of-day penalty and tradeoff between levels of overflights
Authors: Miedema Henk M. E. , Vos Henk , de Jong Ronald G.
Published: July 2002

A decrease in the level of sound events can compensate for an increase in the level of other events, but noise metrics assume different tradeoffs. Noise metrics also differ in the penalty applied to noise in the evening and to noise in the night, and in the definition of these periods. These two aspects of noise metrics, i.e., the tradeoff and the penalty for the nighttime (23–7h), are investigated. A general model of the relation between SELs of sound events (aircraft overflights) and noise annoyance is presented which allows for a wide range of tradeoffs and time-of-day penalties. The (tradeoff and time-of-day penalty) parameters of the model are fitted to the data from an aircraft noise study conducted around Amsterdam Airport Schiphol, which is especially suited for investigating the tradeoff and time-of-day penalties. It was found that in this study the tradeoff between the levels of events in metrics based on LAeq’s, such as LAeq(24 h), DNL, and DENL, is approximately correct for the prediction of noise annoyance. Furthermore, it was found that the strongest correlation with annoyance is obtained with a nighttime penalty of circa 10 dB. No suitable data were available for further tests of the tradeoff. The result with respect to the nighttime penalty was weakly further supported by the outcome of analyses of the original data from four other aircraft noise surveys (one survey conducted around British airports, and three coordinated surveys carried out around Paris Orly, Amsterdam Schiphol, and Glasgow Abbotsinch).