bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of distance and sound recording system on intelligibility and depth localization in highly reverberant conditions
Authors: Ruiz Robert , Ballet Isabelle
Published: July 2002

Speech intelligibility degrades when the listener moves from the source. In a highly reverberant and empty church, scores are measured at different distances from a loudspeaker and compared with those obtained from recordings of the speech at the same location. The phonetic material is a set of phonetically balanced lists of triphonemic French words. Two monophonic (omnidirectional, cardiod) and one stereophonic (ORTF) systems are used. Listening of recorded lists is performed with the same loudspeaker(s) as in the church. Results of the experiment indicate smaller variations of scores with the distance. An important improvement of scores is obtained with the stereophonic system. A second experiment consists of using a sound material composed of two voices performing a singing exercise edited in monophony in order to create two distinct sound planes. Listening tests allow the quantiication of the depth localization variations with distance and sound recording system. Results show a good respect of distance and reveal a sudden change in depth localization for stereophony. Acoustical properties of the church, distance factors of the microphones, properties of the stereophony against monophony, and real listening conditions are considered to discuss the experiments.
Dependence of scattered acoustical signal intensity on the form of distribution of plankton concentration
Authors: Gorska Natalia , Klusek Zygmunt
Published: July 2002

Sounding of the plankton aggregation which consists of identical statistically uncorrelated particles by a plane monochromatic wave has been studied. Analytical formulas for scattered signal intensity and interference coefficient have been obtained for an arbitrary plankton spatial distribution form. The role of interference of waves scattered by individual plankton targets has been under investigation. The influence of the plankton probability density function form on the sounding signal mean intensity has also been considered.
The magical “wave” seven, plus or minus two?
Authors: Wong Willy , Mori Shuji
Published: July 2002

The idea of the magical number seven has been with us for over 40 years now. During this time, it has been studied extensively by both psychologists and other sensory scientists. One might be skeptical about any new results and ask “What more possibly can we say about this topic?” However, in this paper, an attempt is made to refine the interpretation of the magical number by demonstrating that it is not so much a number, but actually a “wave.” That is, independent of both experimental fluctuations and statistical bias, the magical number takes on a continuum of possible values. This prediction, made theoretically, is supported by existing experimental data. While this prediction does not amount to any significant change to the understanding of the magical number, it may however provide a criterion to judge the acceptability of any theory that purports to explain the magical number phenomenon.
Some considerations concerning replicated spectra
Authors: Assaad Jamal , Rouvaen Jean Michel
Published: July 2002

The aim of this paper is to clarify the effect replicated sources in two-dimensional radiation problems. In fact, it will be shown that the discrete pressure computed by using the angular spectrum approach is equal to the analytical pressure plus error terms arising from the convolutions of replicated spectra of the original spectrum and the Green’s function. A similar result is obtained for the far-field discrete pressure. For the later case, it will be shown that errors can be eliminated by choosing a sampling step smaller to that given by the Nyquist criterion.
Boundary effect on a parametrically excited soliton
Authors: Wang Xinlong
Published: July 2002

It has been proved experimentally that a boundary has the “mirror effect” on a parametrically excited soliton. The numerical simulation with the parametrically driven and damped nonlinear Schrödinger equation reproduces the observed interesting phenomena, in particular, the periodical collisions and reflections of the boundary soliton. The dynamical behaviors of the soliton are further concluded as a stability diagram in the space of control parameters. In addition, the internal dynamics including the collision-reflection mechanism of the boundary soliton is also explored tentatively.
Measurement of several types of ‘‘deer whistles’’ for motor vehicles: Frequencies, levels, and animal threshold responses
Authors: Scheifele Peter M. , Browning David G. , Scheifele Lesa M.
Published: July 2002

Small plastic whistles, commonly called ‘‘deer whistles,’’ which are attached, usually in pairs, to the front bumper of motor vehicles are sold to assist in preventing vehicle–deer collisions, an increasingly common road hazard. At vehicle speeds greater than 30 mph (15 m/s) the air forced through these whistles supposedly produces one or more tones which alert a deer or other wild animal of the vehicles approach in time to, hopefully, avoid a damaging collision. Some whistles are advertised to be in the ultrasonic range (typically 18–20 kHz), while others only mention ‘‘high’’ frequencies. Several have a high-frequency (open ended) and low-frequency (close ended) pair. Measurements of frequency and levels for several different whistles are presented. The possible affect on deer and other animals (such as a dog in the vehicle), based on hearing thresholds and ambient noise conditions, is discussed.
Annapolis Laboratory contribution to reduction and isolation of shipboard noise
Authors: Denham James R.
Published: July 2002

The Annapolis Laboratory of the Carderock Division of the Naval Surface Weapons Center has continually been in the forefront in development of hardware and criteria for reducing and isolation of shipboard noise. The laboratory has achieved major reductions in noise generated by pumps, fans, and valves. Their efforts have also resulted in improved damping treatments for piping and foundations.
N-best breadth search for large vocabulary continuous speech recognition using a long span language model
Authors: Yuk DongSuk , Che ChiWei , Raghavan Prabhu , Chennoukh Samir , Flanagan James
Published: July 2002

In a large vocabulary continuous speech recognition system, high-level linguistic knowledge can enhance performance. However, integration of high-level linguistic knowledge and complex acoustic models under an efficient search scheme is still problematic. Higher-order n-grams are so computationally expensive, especially when the size of vocabulary is large, that real time processing is not possible yet. In this report, the n-best breadth search algorithm is proposed under the framework of the state space search, which can handle higher order n-grams and complex subword acoustic models such as the cross-word triphones. The n-best breadth search is a combination of the best first search and the breadth first search. The proposed algorithm can be extended to handle other types of language models such as the stochastic context-free grammar, and different types of acoustic models including the neural networks. Compared with the conventional beam-search method, this pilot experiment shows that the proposed algorithm decreases execution time with little effect on performance. [This research was supported by ARPA Contract No. DABT63-93-C-0037.]
Low-grazing-angle monostatic acoustic reverberation from rough seafloors
Authors: Greaves Robert J. , Stephen Ralph A.
Published: July 2002

The objective of this research is to interpret matched-filtered, beamformed monostatic acoustic reverberation data acquired when the seafloor is insonified by a bandlimited, low-grazing-angle acoustic pulse. This paper addresses the hypothesis that observed backscatter signals are produced by a combination of seafloor (interface) and subseafloor (volume) scattering from structure having variations at scale lengths comparable to the wavelength of the insonifying acoustic field. Numerical modeling, using a finite-difference solution to the elastic wave equation, is performed to quantitatively predict the monostatic acoustic reverberation signals from rough seafloor, with and without subseafloor volume heterogeneity. Wavelength-scale seafloor roughness and subseafloor volume heterogeneity are defined using stochastic distributions with Gaussian autocorrelations. Modeling results show that scattering from rough, basaltic bottoms is dominated by interface scattering. Subseafloor volume heterogeneity is shown to be capable of producing scattered signals comparable to rough seafloor scattering when the bottom is smooth and/or has a low velocity.
Merrill Auditorium/Portland City Hall Auditorium renovation
Authors: Dugger Edward
Published: July 2002

The Portland City Hall Auditorium, Portland, Maine, built in 1912, was specifically constructed for pipe organ recitals and lectures. Over the years, the hall had gone through several renovations and adjustments to further increase its functional use while keeping the Kotzmar Organ as a key feature of the hall. This paper will discuss the changes in the acoustic character of the hall as it went through the various renovations leading to its final version as a multipurpose venue. Comparisons of the original hall’s acoustic characteristics and measurements will also be used to verify the acoustician’s design criteria to the recently completed project. Additional insights into architectural, structural, mechanical and electrical system design for pipe organ rooms will also be offered.
Shallow-water ambient noise from snapping shrimp and dolphins
Authors: Au Whitlow W. L. , Lammers Marc O. , Banks Kiara
Published: July 2002

Snapping shrimp are among the major sources of biological noise in shallow bays, harbors, and inlets, in temperate and tropical waters. Snapping shrimp sounds can severely limit the use of underwater acoustics since their snaps are very broadband with energy from several hundred Hertz to 200 kHz. Snapping shrimp noise is always present having little diurnal and seasonal variations. Peak-to-peak source levels can be as high as 189 dB re:1 μPa. Dolphin emissions are another common source of biological noise. Dolphin sound emissions can be categorized as whistles, burst pulses, and echolocation clicks. Whistles usually contain energy in the 5–20-kHz range, although higher-order harmonics can extend beyond 100 kHz. Burst pulse signals and echolocation clicks are broadband, short duration signals with frequency components beyond 150 kHz. Peak-to-peak source levels of echolocation signals can be as high as 220–225 dB re:1 μPa. Burst pulses are similar in shape to echolocation clicks but with about 6–10-dB lower amplitude. Interclick intervals for burst pulses are about 2 to 3 ms or less and about 20–30 ms for echolocation signals. Dolphins often swim through an area and then leave, whereas snapping shrimps are forever.
Exploring the form and function of biological sounds in shallow water from the perspective of a systems designer
Authors: Ellison William T. , Clark Christopher W.
Published: July 2002

The potential utility of biological sounds is examined from a sonar system perspective. Evaluation of the temporal, spatial, and spectral properties of these sounds from a system designer’s view can provide significant insight as to their possible function. The broadband sonar equations for both passive and active operations are used to evaluate this functionality with special attention paid to issues of shallow water propagation as well as those sound properties that most affect signal processing; time-bandwidth product, spatial and temporal resolving characteristics, and signal repetition rate. Specific examples are used to illustrate these findings, including blue and fin whale calls recorded off the coast of Southern California, bowhead whale calls from the spring migration off the coast of Barrow, Alaska, and humpback whale sounds recorded off the island of Hawaii. The use of a systems approach to evaluating biological sounds can also provide insight into several related areas of recent interest: (1) the effects biological sounds may have on man-made systems, (2) the effect man-made sounds may have on the ability of animals to communicate as well as acoustically sense their environment, and (3) designing underwater experiments to evaluate these issues.
Determination of the driving signal parameters to maximize the performance of a piezoceramic inchworm actuator
Authors: Frank Jeremy E. , Koopmann Gary H. , Lesieutre George A. , Chen Weiching
Published: July 2002

A series of linear piezoceramic inchworm actuators with various applications have been developed. There are three active piezoceramic elements within the inchworm: two ‘‘clamps‘‘ and one ‘‘pusher,’’ each of which is driven independently with a voltage of up to 120 V. Large displacements are achieved by repetitively advancing and clamping the pushing element, with each small step on the order of 10 μm. A program using labview software is used to generate the driving signals to the clamps and pusher. With this program, experiments are performed to study the dynamics of the system, and in particular to identify the conditions for maximum force and velocity as well as the onset of resonance within the clamp and pusher elements. The maximum frequency, force, and velocity for the inchworm are shown to depend on the end loading condition, the type of load (mass or spring), as well as the input signal parameters, which are the frequency, phasing amplitude, and shape of the waveforms. The result of the experimentation is a set of waveform parameters that optimizes the inchworm performance for a specific loading condition.
Modification of sonic boom waveforms during propagation from the source to the ground
Authors: Bass Henry E. , Raspet Richard , Chambers James P. , Kelly Mark
Published: July 2002

A number of physical processes work to modify the shape of sonic boom waveforms as the waveform propagates from the aircraft to a receiver on the ground. These include frequency-dependent absorption, nonlinear steepening, and scattering by atmospheric turbulence. Reflections from the ground can also affect the waveform received by a listener above the surface. In the past two decades, each of these effects has been introduced into numerical prediction algorithms and results compared to experimental measurements. There is still some disagreement between measurements and prediction, but those differences are now in the range of tens of percent. The processes seem to be understood. The present understanding of sonic boom evolution will be presented along with experimental justification.
Open office acoustics and productivity
Authors: Roy Kenneth P.
Published: July 2002

Since its introduction in the 1960s, open office design has been driven by a need for lower cost, increased flexibility, and enhanced worker productivity. The first two can be easily evaluated, but what about ‘‘knowledge worker’’ productivity? The objective in open office design is to have speech intelligibility within a work space, and speech privacy between adjacent work spaces. This paper presents a first step in evaluating knowledge worker productivity as affected by the acoustic design of the space. Six large companies participated in a study on worker satisfaction and perceived effectiveness both before and after acoustic modifications of their workspace. Even a small increase in worker productivity will warrant incremental investments in acoustic treatments since the productivity payback is relatively short. Accordingly, the facility manager needs to consider the building space as a worker productivity ‘‘tool,’’ and not just a space in which to work.
Speech privacy between closed and open offices
Authors: Roy Kenneth P.
Published: July 2002

Speech privacy between closed and open office spaces is dependent on the noise reduction between the spaces, and the background sound available in the receiving space to mask the intruding speech. System performance was evaluated between both pairs of closed spaces, and closed to open space. Ceilings included both light and air supply devices, and the walls included typical door and utility features. The speech privacy was evaluated based upon both objective and subjective measures of performance. The objective response was calculated based on the articulation index (AI), and the subjective response included both PB word lists and continuous discourse (CD). Proper choice of ceiling and wall materials and system design, in combination with electronic masking sound, will provide adequate speech privacy.
A new approach to seismic wave propagation in unconsolidated and consolidated porous media
Authors: Buckingham Michael J.
Published: July 2002

Compressional and shear waves in porous media, including saturated marine sediments and dry sedimentary rocks, exhibit an attenuation that scales as the first power of frequency. Biot developed a theory of wave propagation in such materials in which the dissipation was taken to be viscosity of the pore fluid. This, however, yields an attenuation that scales as the square of frequency below some threshold frequency, above which it converts to the square root of frequency. Recently, Buckingham developed an alternative wave theory of porous media in which the dissipation arises from stress relaxation at grain boundaries. Such a mechanism is consistent with the fact that stress and strain in porous media do not follow one another instantaneously. With an appropriate choice for the internal material response function, representing a time-dependent stick-slip process between grains, it turns out that the attenuation scales as the first power of frequency, in accord with observations. Moreover, the dissipation also introduces stiffness into the material, allowing it to support shear, even though the elastic modulus of the medium may be identically zero. These new ideas will be explored in the presentation, and the theoretical predictions will be shown to be consistent with experimental data.
Acoustic condition monitoring
Authors: Finch Robert D.
Published: July 2002

For a number of years railroad wheels were used as test objects in developing acoustic signature monitoring techniques. This work will be reviewed as well as later laboratory studies using beams to determine the sensitivity of the method. Cracks and other defects can cause shifting and splitting of resonance frequencies, so that these changes can be used to indicate the presence of a defect. The limitation of the vibration monitoring method is that other conditions, such as uncertainties in the geometry of the test object, its surface conditions, and loading can also affect the vibration response, and it is necessary to distinguish the effects due to harmful conditions from those due to harmless ones. The sensitivity of the method is thus determined by the need to make this distinction. The concepts will be illustrated with experimental results from a test fixture for the case of a slotted steel beam, assuming that a slot can be used as a model for a crack. Some experiments with concrete beams will also be viewed.
Nondestructive free oscillation method of crack evaluation
Authors: Bouraou Nadejda I. , Boyarchuk Anatoliy A. , Gelman Leonid M.
Published: July 2002

For nondestructive evaluation of the relative size of a fatigue crack the acoustical free oscillation method is used. The testing object model as a nonlinear oscillator is considered. Object natural frequency shift is used as a testing data. The maximum likelihood equation is solved. New expressions of the relative crack size estimate are received.
Animal bioacoustics in the lab: Some hows and whys of six-legged listeners
Authors: Farris Hamilton
Published: July 2002

Animal bioacoustics is an interdisciplinary field that may employ concepts from physical acoustics, psychoacoustics, neurobiology, and evolutionary biology to examine the characteristics of sound production and hearing in nonhuman animals. Most of the public’s attention to bioacoustics focuses on the acoustic behavior of some of our close mammalian relatives and birds, but equally elaborate acoustic signals have evolved in a wide variety of taxa including many insects. These signals function in such diverse contexts as communication among conspecifics, detecting and avoiding predators, and locating appropriate habitat. For example, as a consequence of the selective pressure from insectivorous bats which echolocate their prey using ultrasound, several insects have evolved ultrasound sensitivity. When presented with ultrasound, these insects perform evasive behaviors that function in bat avoidance. Demonstrations here will show how the ultrasound-induced startle response is a useful behavioral assay for auditory sensitivity in certain insects (e.g., crickets and beetles). This experimental paradigm can thus be used to teach the laboratory methods required for measuring the characteristics of a sensory system as well as interpreting the evolutionary contexts in which the sensory system has evolved. [Work supported by NIMH.]
Speech acoustics: Vocal tracts, synthesizers, and talking heads
Authors: Rubin Philip
Published: July 2002

This presentation provides an introduction to human speech acoustics for a general audience. Acoustic signals are created in humans by a complex sound production system. The nature of this elegant sound-producing device will be shown in a number of ways, including demonstrations of the source-filter model of sound production and an articulatory model that produces sound by attempting to capture what is going on in the vocal tract during speech production. Real listeners do not attend solely to the acoustic signal. Information is available in a number of domains, including visual and tactile. The multimodal nature of speech will be demonstrated by the McGurk effect. Recently there has been considerable interest in the study of audiovisual speech. A portion of the Talking Heads website will be shown illustrating the international excitement in developing aesthetically pleasing and intelligible ‘‘talking heads.’’ This approach is of interest to a variety of different groups, including those concerned with language training for the hearing-impaired, the film industry which is interested in increasingly realistic virtual actors and animations, and human-interface developers working on avatars and virtual humans. The presentation will close with a mention of other web resources and teaching tools related to speech acoustics.
Acoustic levitation of drops in air
Authors: Holt R. Glynn , Clarke Corey C. , Wyatt Sean C.
Published: July 2002

The nonlinear interaction between an acoustic field and an inclusion possessing acoustic properties that are different from the host medium can, among other effects, yield a net body force on the inclusion. If the vertical component of the field gradient is sufficient (i.e., that of a standing wave) and its amplitude large enough, the force of gravity can be balanced—an effect commonly known as ‘‘acoustic levitation.’’ Acoustic levitation has been used in a wide variety of scientific studies, among them studies of sonoluminescing bubbles and investigations of liquid drop dynamics and surface rheology. A monofrequency air levitator will be demonstrated, and several aspects of drop physics will be illustrated by acoustically manipulating the drops. [Work supported by NASA.]
European product noise emission labeling and reporting requirements
Authors: Hellweg Robert D.
Published: July 2002

There are several different types of European requirements on providing product noise information to the purchaser or user of those products. This paper describes and presents details of existing and proposed European product noise labeling and reporting requirements. They may be classified into five general categories: (1) national, European, and International consensus standards; (2) legal requirements, e.g., European Directives and the consensus standards that have been promulgated in support of them; (3) purchase specifications; (4) manufacturers declaration of conformance standards; and (5) voluntary environmental labels or ‘‘Eco-labels’’ for certain product types which contain acoustical limits and imply the acoustical acceptance of products displaying the Eco-label. Experiences with the European requirements should be considered by the members of ANSI S12 Working Group 38 in the development of an American standard on product noise labeling.
Application of resonant ultrasound spectroscopy to geomaterials
Authors: Matveyev Alexander L. , Sutin Alexander M. , Potapov Andrey I. , Johnson Paul A.
Published: July 2002

Our objective is to apply resonant ultrasound spectroscopy (RUS) for obtaining the full elastic tensor of geomaterials. To our knowledge, RUS has never been successfully applied to complex materials such as rock: materials that are anisotropic and often inhomogeneous, and that contain grain-to-grain contacts, microcracks, etc. The fundamental problem with applying RUS to rock is high dissipation in the material, and the problem of coupling into all possible modes. The high dissipation limits the frequency band, and coupling into all modes controls the outcome of whether or not the full elastic tensor can be obtained. Our current experiment is operable in the frequency band of 3–30 kHz. Numerous sensor positions were tested in order to excite and detect different resonant modes. To date, the method has been applied to a rectangular brick sample. The comparison with theoretical calculation demonstrates that all modes (eigenfrequencies) of the sample were detected with high accuracy. Preliminary testing on cylindrical sandstone samples was also carried out. Duplicating the result from the brick in the rock sample is in progress. [This work is supported by the United States Industry Coalition, with the US DOE Contract W-7405-ENG-36, through the University of California.]
The first pitch-shift effect as a Doppler effect. A simple physical explanation to a complex perceptual phenomenon
Authors: Vassilakis Pantelis N.
Published: July 2002

The first pitch-shift effect describes the relationship between pitch and center frequency of complex stimuli with equally spaced components and fixed frequency spacing: f0. It is described mathematically by a saw-tooth function in a model introduced by de Boer [Doctoral dissertation, University of Amsterdam (1956)]. Researchers usually favor a more ambiguous frequency-shift/pitch-shift relationship that better justifies the generally accepted explanation (perceptual detection of a wave signal’s time-fine-structure). Pilot experiments, however, indicate that: (a) the patterned pitch ambiguities reported by previous studies may be artifacts of experimental design, not challenging de Boer’s model, and (b) no model accounts for the present study’s reported pitch for frequency shifts: f0/2. The explanation introduced presently argues that (a) modulations resulting from wave superposition are waves themselves, with velocity (:VGroup) that is independent from the velocity of their constituent components (:VPhase), and (b) uniform frequency shifts of a complex wave’s components change the relationship between VGroup and VPhase, changing the effective frequency of the emerging modulations relative to a fixed point in the medium of propagation. These relative speed/frequency changes predict pitch shifts that agree with observation (including the case of frequency-shifts: f0/2), making the first pitch-shift effect a version of the Doppler effect.
The effect of middle ear resonant frequency, ear canal resonance, and ear canal volume on TEOAE
Authors: Jupiter Tina , Giacomazza Shannon
Published: July 2002

It is well known that there is a large inter-individual variability in the size of the TEOAE. Quantifying the sources of variability can help to determine the influences of some of the factors that can affect test results. The difference found in TEOAE may be due to the difference in size and shape of the ear rather than cochlear mechanics. The effect of ear canal volume between the probe and the tympanic membrane influences the intensity and spectrum of the stimulus as well as the characteristics of the response. A small ear canal volume should result in a higher stimulus sound-pressure level. This can determine both the effectiveness of the evoking stimulus as well as the response that is measured. We will report results of the study of the relation between ear canal volume, ear canal resonant frequency, and resonant frequency of the middle ear on TEOAE for 20 normal hearing young adults. The purpose is to determine if the characteristics associated with TEOAE are influenced by middle ear resonance and ear canal resonance and volume. By quantifying some of the variables that can effect TEOAE the test interpretation may be clarified.
Multidimensional scaling of judgments on tinnitus and imitation tinnitus
Authors: Zhang Tao , Penner Merrilynn J.
Published: July 2002

Sixteen normal subjects were asked to judge the dissimilarity between any pair of stimuli chosen from 13 imitation tinnitus. Six tinnitus subjects were asked to perform the same task on 13 imitation tinnitus plus their own tinnitus. Multidimensional scaling was used to analyze the dissimilarity data and to provide a geometric representation. For 13 imitation tinnitus, there was no significant difference between the judgments by normal subjects and tinnitus subjects. All subjects distinguished imitation tinnitus mainly based on the overall sensation level. The frequency at the center of gravity of the stimulus spectrum played a secondary role in the judgments. Each tinnitus subject perceived their own tinnitus and its imitation in a similar way. With respect to the current stimulus set, imitation tinnitus was a good, but not the best, simulation of the corresponding tinnitus. [Work supported by NIH.]
Numerical prediction of noise radiated from a panel subjected to boundary layer excitation
Authors: Allen Michael J. , Vlahopoulos Nickolas
Published: July 2002

In this work an algorithm is developed for combining finite element and boundary element techniques for computing the noise radiated from a panel subjected to boundary layer pressure loading. The excitation is presented in terms of the auto and cross power spectral densities [F. Han, ‘‘Measurement of pressure fluctuations under turbulent boundary layer,’’ Ray W. Herrick Laboratories, Report-213, HL 97-14, Purdue University]. The structural finite element model for the panel is divided into a number of sections. A uniform pressure is applied as excitation on each section separately. The corresponding vibration is computed, and is utilized as excitation for an acoustic boundary element analysis. The acoustic response is computed at any data recovery point of interest. The relationships between the acoustic response and the pressure excitation applied at each particular section of the panel constitute a set of transfer functions. They are combined with the spectral densities of the excitation for computing the noise generated from the vibration of the panel subjected to the boundary layer excitation. This development has the potential of computing wind noise in automotive applications, or boundary layer noise in aircraft applications. [Work supported by Rackham School of Graduate Studies, Univ. of Michigan, and Ford Motor Co.]
Radiation efficiency of convected fluid-loaded plates
Authors: Frampton Kenneth D.
Published: July 2002

The radiation of sound from geometrically simple vibrating structures into stationary fluids is well understood. However, to date, very few investigations have considered the effects that a convected fluid has on structural acoustic radiation. The purpose of this investigation is to quantify the effects of various structural and fluid parameters on the sound radiated from a vibrating elastic plate into a convected fluid medium. The discussion will include a description of modeling an elastic plate imbedded in an infinite baffle and coupled to a semi-infinite convected fluid field. Furthermore, the importance of a coupled model approach (where the fluid pressures generated by the plate motion in turn force the plate response) will be discussed. The influence of several system parameters on the plate radiation efficiency will be discussed. Included in these parameters are the fluid velocity, plate aspect ratio, fluid-to-plate mass ratio, and others. It will be demonstrated that the effects of convected fluid loading on sound radiation can be very significant.
Direct numerical simulations of impulsively started jets with application to speech production
Authors: Mongeau L. , Frankel S. H. , Scherer R. C.
Published: July 2002

Many aspects of the conversion of the air flow through the larynx into sound are still insufficiently understood for the purposes of making precise diagnostic decisions in the voice clinic, targeting optimal intervention strategies for voice problems and voice training, and achieving high-quality articulatory speech synthesis. In a previous study, experiments performed using a dynamic physical model of the larynx revealed the presence of a transient pulse occurring immediately after the instant of vocal fold separation, prior to the formation of a quasisteady developing jet [Mongeau et al., J. Acoust. Soc. Am. 102, 1121–1133 (1997)]. The purpose of the present study was to investigate this phenomenon numerically using direct and large eddy simulations of an impulsively started free planar jet. The compressible Navier–Stokes equations were integrated using a two–four compact finite-difference scheme. A nonuniform Cartesian grid was used with Navier–Stokes characteristic boundary conditions. Preliminary results confirmed the presence of an acoustic pulse immediately following the imposition of a pressure gradient across the orifice. The feasibility of extending this conclusion for the case of three-dimensional confined jets will be discussed. [Work supported by NIH.]
The coarticulation of coronal stops: A modeling study
Authors: Ericsdotter Christine , Lindblom Björn , Stark Johan , Sundberg Johan
Published: July 2002

Articulatory data were obtained from x-ray films [P. Branderud et al., Fonetik 98, 168–171 (1998) and www.ling.su.se/fon/publications/] and analyzed by finding the best-matching profiles generated by APEX, an eight-parameter speech production model developed at SU and KTH [J. Stark et al., Fonetik 98, 184–187 (1998)]. APEX was calibrated to reflect the vocal tract characteristics of individual subjects and the vowel-dependent movements associated with dental and retroflex Swedish stops were depicted as trajectories in the APEX parameter space. The mapping of x-ray observations onto APEX parameters provides an opportunity to reexamine traditional issues arising in the context of coarticulation. The results will be compared with quantitative predictions derived from Döhman’s ‘‘uniform coarticulation’’ formula [J. Acoust. Soc. Am. 41, 310–320 (1967)] and from alternative hypotheses based on APEX parameter optimization. [Work supported by the HSFR and RJ research councils of Sweden.]
Open-phase integrated sound pressure as a tool for analyzing factors that affect glottic source wave
Authors: Elder S. A. , Castellanos P. F.
Published: July 2002

For experimental situtions such as Sondhi tube and low-voice anechoic chamber measurements, where head resonance and room reflection contamination of the glottic source wave are small, the open-phase single glottic pulse of integrated sound pressure is a useful tool for assessing conditions of sound generation in the larynx. In some cases this parameter becomes a surrogate glottic area function, while in others it mimics the DEGG, suggesting a second sound source associated with the switching on and off of the glottic jet at the beginning and ending of open phase. Like the EGG, integrated sound pressure (ISP) has the advantage of being noninvasive and could be useful for screening pathological laryngeal conditions. Examples are presented for both in vitro and in vivo phonation of single glottic pulses (SGP).
Detecting hesitations in the automatic recognition of spontaneous speech
Authors: O’Shaughnessy Douglas , Lee Clark Z. , Tolba Hesham , El Meliani Rachid , Li Weiying , Wang Zhong-Hua
Published: July 2002

Practical speech recognizers must accept normal conversational voice input (including hesitations). However, most automatic speech recognition work has concentrated on read speech, whose acoustic aspects differ significantly from speech found in actual dialogues. Hesitations, filled pauses, and restarts (after aborted utterances) are common in natural speech, yet few recognition systems handle such disfluencies with any degree of success. Among other problems, filled pauses (e.g., ‘‘uhh,’’ ‘‘umm’’), unlike silences, resemble phones as part of words in continuous speech. The work reported here further develops techniques to allow identification of filled pauses. The problem of finding and correcting restarts is also examined, i.e., not just determining where the speech interruption occurs, but also estimating which words are undesired. The Switchboard database (of natural telephone conversations, yielding relatively poor recognition rates to date) provided data for the study. While most automatic reognition methods rely entirely on spectral envelope (e.g., low-order cepstral coefficients), identifying hesitation phoenemena requires using a combination of spectra, fundamental frequency and duration.
Real-world performance of headset active noise reduction systems
Authors: Crabtree R. B.
Published: July 2002

Active noise reduction (ANR) in headsets promotes the electro-acoustic cancellation of sound within the ear cups of a hearing protector. Operating at frequencies below 1000 Hz, ANR augments attenuation where passive protection is minimal. Personal ANR can reduce the potential for hazardous noise exposure and can facilitate auditory communications. ANR system performance has been characterized to assist purchasing departments in making informed decisions about commercial devices suitable for use in high-noise environments such as helicopters and tracked vehicles. Test methods were developed to assess: (a) active attenuation properties, (b) issues of fitting integrity, (c) speech discrimination performance, (d) saturation or overload threshold limit, and (e) general suitability for long-term use. When properly designed and applied, personal ANR can enhance the listening environment for the user. Nonetheless, performance limitations have been identified in certain devices. Some tended to overload easily or to cease operating under adverse conditions, and others became unstable when the seal around the ear was broken. Proper fitting is pivotal to satisfactory ANR operation, particularly in units with low overload tolerance. Ultimately, the function of any ANR system must be understood in relation to its intended operating environment.
A new method for calculating temporal intensity correlations in partially saturated scattering
Authors: Gerber James S.
Published: July 2002

Intensity correlations in time for acoustic scattering from internal waves are investigated using path integral methods. A new perturbative procedure for calculating the temporal intensity autocorrelation 〈I(x,0)I(x,t)〉, valid in the partially saturated scattering regime, is introduced. Partial saturation describes a situation in which smaller scales of the scatterer cause the geometrical raypath to fracture into myriad microrays but where the larger scales lead to correlation between these micromultipaths. This situation is of particular relevance in acoustic propagation through internal waves due to the wide range of vertical scales as well as the separability of the internal wave power spectrum. It is shown that the perturbative method being introduced has greater accuracy as well as a wider range of applicability than the standard method [Flatté et al., J. Acoust. Soc. Am. 77, 1723–1731 (1985)]. A computer simulation of acoustic propagation through an evolving internal wave field has been implemented to provide a basis for comparison with the theory. Application to calculation of higher moments of intensity will be discussed. [Work supported by ONR.]
Mode coupling in the presence of random sediments and shallow water variability
Authors: Oba Roger M.
Published: July 2002

The continental shelf west of Florida has a relatively flat bottom over a range of tens of kilometers, and the bottom and water column have fairly well characterized acoustic parameters. Parabolic equation models are used for acoustic propagation in both elastic and purely acoustic cases. The calculated effect of shear contribution is comparatively small. The variation in mode coupling over a frequency range of about 100–400 Hz is evaluated. Even in this flat-bottom case, modal coupling due to the environment occurs, especially at lower frequencies. The water column tends to be downward refracting (especially the bottom half), so that the variation in the penetrability of the sediment leads to strongly changing amounts of mode coupling. In the case of softer bottoms, this can lead to very significant coupling. [Work supported by the Office of Naval Research.]
Geoacoustic inversions using light bulb sound sources and measurements of the bottom-reflected acoustic field
Authors: Taroudakis Michael , Papadakis Panaghiotis , Chapman N. Ross , Jaschke Lothar
Published: July 2002

The paper presents results of geoacoustic inversions obtained using a direct inversion scheme based on the calculation of the reflection coefficient of a stratified elastic bottom. The reflection coefficient has been derived from measurements of the acoustic field at a vertical line array of hydrophones moored in the area of the Haro Strait, during the PRIMER sea trial that was carried out in June 1996. Light bulbs have been used as acoustic sources with peak power around 600 Hz. Inversions for the sound speed, the density, and the shear speed of a sediment layer and a semi-infinite substrate and the thickness of the sediment have been performed by separating the various echoes at the receiver and identifying their type through a multiple stage optimization procedure. The results are compared with matched field inversions and a good agreement is demonstrated especially for the parameters of the sediment layer. The applicability of the new method for different experiment setups is also discussed.
High-frequency forward scatter and propagation experiments in the Delaware Bay
Authors: Qin Wenkai , Badiey Mohsen , Zagar Randy , Simmen Jeff
Published: July 2002

In order to assess the temporal and spatial coherence of transmitted broadband acoustic signals (1–20 kHz) in coastal environments, two acoustic experiments were performed in the Delaware Bay during March and September 1997. Accompanied by measurements of the ocean volume (temperature and salinity) and sea surface roughness (0- to 0.5-m wave height), these acoustic experiments included reciprocal acoustic transmissions over a large band of acoustic frequencies and during a variety of sea states. The connection between the stability and coherence of the single surface bounce and the sea surface roughness is studied. In the presence of rough seas (and therefore bubbles), the coherence decreases rapidly between reciprocal receptions as sea state increases, while for calm sea states a high correlation exists between them. Some preliminary modeling results using a high-frequency parabolic equation (PE) model are used to interpret this frequency-dependent behavior.
Computed time-reversing array retrofocusing in a dynamic shallow-water sound channel
Authors: Dungan Michael R. , Dowling David R.
Published: July 2002

A time-reversing array (TRA) can retrofocus acoustic energy to the location of its original source even when the acoustic environment is complex and unknown. However, array performance is degraded when the acoustic environment is time dependent. Predictions of array retrofocusing performance require an acoustic propagation model for the environment. The model used in this study is a parabolic equation (PE) code (RAM by M. D. Collins). This study addresses the sensitivity of TRA retrofocusing to time variation in the water column of a shallow-water sound channel. These changes include internal waves and tidal fluctuations. Simulated variations are based on measured oceanic statistics. The influence of waveguide complexity on retrofocusing is also determined by adding range dependence and realistic bottom properties to the computational domain. Results are presented for a variety of ranges and acoustic frequencies. [Work supported by the Office of Naval Research, Ocean Acoustics.]
Variability of highway noise barrier insertion loss in the atmosphere
Authors: Hansen Scott D. , Burroughs Courtney B.
Published: July 2002

Measurements of insertion loss of a model highway noise barrier were performed at the Pennsylvania Transportation Institute test track near State College, PA. An array of microphones was used to provide directionality to remove arrivals from other than over the top of the barrier. This eliminated arrivals from the ends of the barrier so that the results can be applicable to an infinitely long barrier. Also, the array is used to identify different propagation paths which contribute to the sound field in the shadow zone. Since the insertion loss depends on distances of the source and receiver from the barrier, measurements were made for different source-to-barrier and barrier-to-receiver distances. An analysis of results was used to determine the dependence of insertion loss on key parameters, e.g., ground impedance, wind speed, and barrier height. Numerical models are exercised to explore the dependencies of insertion losses on parameters not easily changed on site, e.g., ground impedance.
Sound scattering by a stiffened cylindrical shell using elasticity theory
Authors: Baillard A. , Conoir J.-M. , Décultot D. , Maze G. , Klauson A. , Metsaveer J.
Published: July 2002

Previous articles about stiffened cylindrical shells have described acoustic scattering through theory of thin plates and shells. Considering the dimensions of the studied object, these analyses are limited in frequency range (reduced frequency kR<70). The aim of the present work is to first establish a model using elasticity theory and then to validate it in low frequencies with regard to thin shell theory. As this new model allows us to extend the analysis into high frequencies (kR∼50–200), numerical and experimental results are compared in this frequency band in order to determine the effects of the internal plate in the acoustic scattering of the shell. The cylindrical shell is made of stainless steel with an internal-to-external radius ratio b/a=0.98 (medium radius R=25.25 mm). It is stiffened by a wall (of the same material and thickness) which is soldered along two diametrically opposed generatrix of the shell. In the experimental setup, the air-filled shell is vertically immersed in water and normally insonified by a plane wave. The emitter–receiver transducer turns around the object and records the backscattering spectrum at various angles relative to the wall.
Comparison of the acoustic finite element method and the acoustic boundary element method for interior noise prediction
Authors: Sung Shung H. , Nefske Donald J.
Published: July 2002

Comparisons are made of the acoustic finite element method versus the acoustic boundary element method for predicting interior noise in an enclosure. The theoretical formulation of both methods is summarized, and applications are presented of the interior noise prediction in a rectangular box and in the passenger compartment of an automotive vehicle. The accuracy of the predicted results and the computational performance of the acoustic finite element method versus the acoustic boundary element method are compared. The relative advantages and disadvantages of each method are discussed.