bluuebunny/crossref_metadata_2025 huggingface dataset:
A new genetic algorithm technique in optimization of permanent prostate implants
Authors: Yang Guozhen , Reinstein L. E. , Pai S. , Xu Zhigang , Carroll D. L.
Published: July 2002

Real time optimized treatment planning at the time of the implant is desirable for ultrasound‐guided transperineal permanent prostate implants. Currently available optimization algorithms are too slow to be used in the operating room. The goal of this work is to develop a robust optimization algorithm, which is suitable for such application. Three different genetic algorithms (sGA, sureGA and securGA) were developed and compared in terms of the number of function evaluations and the corresponding fitness. The optimized dose distribution was achieved by searching the best seed distribution through the minimization of a cost function. The cost function included constraints on the periphery dose of the planned target volume, the dose uniformity within the target volume, and the dose to the critical structure. Adjustment between the peripheral dose, the dose uniformity and critical structure dose can be achieved by varying the weighting factors in the cost function. All plans were evaluated in terms of the dose nonuniformity ratio, the conformation number and the dose volume histograms. Among these three GA algorithms, the securGA provided the best performance. Within 2500 function evaluations, the near optimum results were obtained. For a large target volume (5 cm×4 cm×4.5 cm) including urethra with 20 needles, the computer time needed for the optimization was less than 5 min on a HP735 workstation. The results showed that once the best set of parameters was found, they were applicable for all sizes of prostate volume. For a fixed needle geometry, the optimized plan showed much better dose distribution than that of nonoptimized plan. If the critical structure was considered in the optimization, the dose to the critical structure could be minimized. In the cases of irregular and skewed needle geometry, the optimized treatment plans were almost as good as ideal needle geometry. It is concluded that this new genetic algorithm (securGA) allows for an efficient and rapid optimization of dose distribution, which is suitable for real time treatment planning optimization for ultrasound‐guided prostate implant.
Nuclear interactions of 160 MeV protons stopping in copper: A test of Monte Carlo nuclear models
Authors: Gottschalk Bernard , Platais Rachel , Paganetti Harald
Published: July 2002

To estimate the influence of nuclear interactions on dose or biological effect one uses Monte Carlo programs which include nuclear models. We introduce an experimental method to check these models at proton therapy energies. We have measured the distribution of charge deposited by 160 MeV protons stopping in a stack of insulated copper plates. A buildup region ahead of the main peak contains ≈20% of the total charge and is entirely due to charged secondaries from inelastic nuclear interactions. The acceptance for charged secondaries is 100%. Therefore the data are a good benchmark for nuclear models. We have simulated the stack using GEANT with two nuclear models. FLUKA agrees fairly well with the measurement but GHEISHA, designed for much higher energies, does not. The experimental method will work for many other materials, including insulators. Therefore it can also be used for light nuclei.
Digital radiography enhancement by nonlinear multiscale processing
Authors: Stahl Martin , Aach Til , Dippel Sabine
Published: July 2002

Today's digital radiography systems mostly use unsharp maskinglike enhancement algorithms based on splitting input images into two or three frequency channels. This method allows fine detail enhancement as well as processing of global contrast (harmonization). However, structures of medium size are not accessible. In extension of a standard algorithm of such type, we develop and test a new enhancement algorithm based on hierarchically repeated unsharp masking, resulting in a multiscale architecture allowing consistent access to structures of all sizes. Our algorithm decomposes a radiograph by a pyramid‐architecture, dividing it into eight or more channels representing structures of different sizes, known as “scales.” At each scale, weakly contrasting structures are then enhanced by suitable nonlinear processing. We emphasize two points: first, backward compatibility to the standard algorithm which is used routinely in clinical practice. This allows reuse of current parametrization know‐how as well as a smooth transition from current to new processing. Second, our enhancement is noise‐resistant in the sense that it prevents unacceptable noise amplification. A prototype implementation of the algorithm is undergoing trials in the clinical routine of radiology departments of major German hospitals. Results strongly indicate the superior performance and high acceptance of the new processing.
Condensation in a steady-flow thermoacoustic refrigerator
Authors: Hiller R. A. , Swift G. W.
Published: July 2002

Condensation may occur in an open-flow thermoacoustic cooler with stack temperatures below the saturation temperature of the flowing gas. In the experimental device described here the flowing gas, which is also the acoustic medium, is humid air, so the device acts as a flow-through dehumidifier. The humid air stream flows through an acoustic resonator. Sound energy generated by electrodynamic drivers produces a high-amplitude standing wave inside of the resonator, which causes cooling on a thermoacoustic stack. Condensation of water occurs as the humid air passes through the stack and is cooled below its dew point, with the condensate appearing on the walls of the stack. The dry, cool air passes out of the resonator, while the condensate is wicked away from the end of the stack. Thermoacoustic heat pumping is strongly affected by the form of the condensate inside of the stack, whether condensed mostly on the stack plates, or largely in the form of droplets in the gas stream. Two simple models of the effect of the condensate are matched to a measured stack temperature profile; the results suggest that the thermoacoustic effect of droplets inside the stack is small.
Conical radiating waves from immersed wedges
Authors: Hladky-Hennion Anne-Christine , Langlet Philippe , de Billy Michel
Published: July 2002

The finite-element approach has previously been used, with the help of the ATILA code, to model the subsonic and supersonic waves in immersed waveguides [A. C. Hladky-Hennion et al., J. Sound Vib. 212, 265–274 (1998)]. This method has given a precise account of the experimental results and has shown the major effects. In this paper, a new representation of radiating waves is presented, leading to a simple understanding of the physical phenomenon: radiating waves are propagating with the same phase velocity on the surface of a cone, the axis of which is the wedge direction.
In situ source level and source position estimates of biological transient signals produced by snapping shrimp in an underwater environment
Authors: Ferguson Brian G. , Cleary Jane L.
Published: July 2002

Biological transient signals produced by snapping shrimp are sensed underwater by a wide aperture array. The instantaneous range and bearing of the source position of each snap is estimated along with a source level equal to the peak-to-peak amplitude of the pressure impulse generated by the snap at a standard distance of 1 m from its point of origin. For a sample of 1000 snaps recorded in Sydney Harbour, the distribution of peak-to-peak sound pressure levels has a mean value of 187 dB (re 1 μPa) and an interquartile range of 185–189 dB (re 1 μPa). Plotting the Cartesian coordinates of the source positions of the biological transient signals over a period of time maps the two-dimensional spatial distribution of the local snapping shrimp population. The principal habitat is found to be geocoincident with a 120-m-long wharf, the closest point of which is 60 m from the middle of the receiving array. The passive ranging performance of the wide aperture array is evaluated by generating mechanical transient signals at selected positions along the wharf. Precise estimates of the relative times-of-arrival of the acoustic wavefronts lead to source range and bearing estimates with standard deviations of only 0.1 m and 0.005 degrees (respectively), in agreement with theoretical predictions.
Middle-ear function with tympanic-membrane perforations. II. A simple model
Authors: Voss Susan E. , Rosowski John J. , Merchant Saumil N. , Peake William T.
Published: July 2002

A quantitative model of the human middle ear with a tympanic-membrane (TM) perforation is developed. The model is constrained by several types of acoustic measurements made on human cadaver ears, which indicate that perforation-induced changes in transmission result primarily from changes in driving pressure across the TM and that perforation-induced change in the structure of the TM and its coupling to the ossicles contributes a substantially smaller component. The model represents the effect of a perforation on the pressure difference across the TM by inclusion of a path for sound coupling through the perforation from the ear canal to the middle-ear cavity. The model implies that hearing loss with perforations depends primarily on three quantities: the perforation diameter, sound frequency, and the volume of air in the middle-ear cavity. For the conditions that produce the largest hearing loss (low frequency and large perforation), the model yields a simple dependence of loss on frequency, perforation diameter, and middle-ear cavity volume. Predictions from this model may be useful to clinicians in determining whether, in particular cases, hearing losses are explainable by the observed perforations or if additional pathology must be involved.
Global damping of noise or vibration fields with locally synthesized controllers
Authors: Yuan Jing
Published: July 2002

A locally synthesized controller (LSC) is one that uses a local feedback signal in a noise or vibration field (VF) to synthesize the actuation signal. The global damping of a VF by available LSCs requires sensor–actuator collocation. This study presents a LSC for the global damping of a VF without requiring sensor–actuator collocation, which is important to noise control applications where a sensor may be placed away from an actuator to avoid the near field effects. It is proven that the LSC damps the entire VF instead of just a local feedback loop. This is different from other LSCs that may control local feedback loops without damping the VFs. A decentralized control law is presented here to extend the LSC to a decentralized damping system using multiple actuators.
A combination of PZT and EMAT transducers for interface inspection
Authors: Na Won-Bae , Kundu Tribikram
Published: July 2002

A PZT (Lead Zirconate–Titanate) transducer requires a couplant to send and receive mechanical waves. This requirement is a major shortcoming of the PZT technique for use in field applications. In the laboratory environment careful considerations and surface treatments are required to use PZT because the couplant can affect the consistency of experimental results. One alternative to overcome this shortcoming is the use of EMAT (ElectroMagnetic Acoustic Transducer). However, EMAT gives relatively low transmitted ultrasonic energy, with low signal to noise ratio, and the induced energy is critically dependent on the probe proximity to the test object. These are not desirable properties for NDT (nondestructive testing) of civil infrastructures. That is why, in this paper, a combination of PZT and EMAT is introduced for investigating reinforced concrete structures. Interface defects between steel bars and concrete are investigated by this technique. It is shown that the PZT–EMAT combination is very effective for steel bar–concrete interface inspection and the guided waves are useful for nondestructive testing of civil infrastructures.
Direct optimization methods, ray propagation, and chaos. II. Propagation with discrete transitions
Authors: Mazur Martin A. , Gilbert Kenneth E.
Published: July 2002

Eigenrays between a source and receiver are classically determined by an initial value or “shooting” approach. In range-dependent environments the ray paths can be chaotic, putting a fundamental limit on the accuracy of classical ray tracing methods. An alternative approach can be based on Fermat’s principle of minimum propagation time. Using the so-called “direct methods” of the calculus of variations, the travel time integral can be minimized directly, rather than by means of the Euler–Lagrange differential equations used in shooting. In the current paper, examples are studied where the changes in a ray’s trajectory occur at discrete points. Discrete mappings, analogous to the Euler–Lagrange equations used in shooting techniques in continuous problems, are introduced. It is demonstrated that direct methods can be applied to the travel time summations in discrete problems, just as they can be applied to the travel time integral in continuous problems. It is shown that direct methods can be used to calculate certain arrivals (e.g., “head waves”) that cannot be produced by shooting. Using discrete examples, direct methods are compared to the more conventional discrete mapping (shooting) approach, without the complications of numerical analysis and infinite dimensionality found in continuous problems. Two examples are studied that are associated with a standard discrete mapping known to be chaotic. Direct methods are used to find eigenrays for these chaotic examples. The advantages and limitations of direct methods in discrete problems with chaos are discussed.
The effect of sound intensity on f1-sweep and f2-sweep distortion product otoacoustic emissions phase delay estimates in human adults
Authors: Bowman Denise M. , Brown David K. , Eggermont Jos J. , Kimberley Barry P.
Published: July 2002

Phase measurements of distortion product otoacoustic emissions (DPOAE) provide an estimate of round-trip travel times in the cochlea. This study examined differences in f1- and f2-sweep round-trip delays estimated from DPOAE phase responses in 20 normal-hearing adult human subjects as a function of f2 frequency and sound intensity. Eight different f2 frequencies ranging from 1.1–13 kHz were presented. For both the f1- and the f2-sweep stimulation conditions the f2/f1 ratios were between 1.1 and 1.3. Primary intensity levels for f2 were varied in 5-dB steps from 30–50 dB SPL (where f1 was 15 dB>f2). Delays in the f2-sweep condition were equal to or longer than travel times in the f1-sweep condition. Round-trip delays showed a significant intensity dependence in both the f1- and f2-sweep conditions (p⩽0.01). In both conditions, the delay increased as stimulus intensity decreased. Delay estimates in the f2-sweep condition were more strongly intensity dependent than estimates in the f1-sweep condition at f2 frequencies above 1.6 kHz. The mean difference in f2- and f1-sweep delays at low intensities ranged from 15.9 periods at the 9.2 kHz f2 place, to 2.5 periods at the 1.6 kHz f2 place. The intensity dependence of round-trip delay estimates in both conditions may be attributed to intensity-dependent changes in the cochlear filter response time related to the sharpness of tuning of DPOAE responses. The steeper intensity dependence and longer delays observed in the f2-sweep condition may similarly be attributed to a greater proportion of the f2-sweep response being composed of the filter response time.
Theory of the background amplitudes in acoustic resonance scattering
Authors: Choi Myoung-Seon , Joo Young-Sang
Published: July 2002

For problems of resonance scattering of acoustic waves from penetrable targets of canonical geometry, a general approach which yields an exact and simple expression, named the inherent background coefficient, for the acoustical background is proposed. By analyzing the effect of the structural damping of targets, it is found that, within each modal surface admittance of targets, including a negligible effect of the structural damping, there are two interacting contributions: a constant contribution and a resonant contribution. The constant contribution, which corresponds to the inherent background coefficient, can be obtained from the zero-frequency limit of an equivalent fluid target. For targets including a significant effect of the structural damping, the inherent background depends on the damping effect. The inherent background coefficients for empty, elastic, spherical shells not including the structural damping effect are shown explicitly. The coefficients are described by a generalization of the fluid-loading parameter. Also, it is analytically and numerically shown that the inherent background undergoes a transition to the rigid or soft background in the appropriate limit, and correctly describes the acoustical background for any shell over all frequencies.
Acoustic propagation in the presence of an arbitrary flow
Authors: Peyret C. J.
Published: July 2002

The study of acoustic propagation in a lined duct in the presence of an arbitrary flow remains open. Duct acoustic propagation in the presence of flow is generally computed assuming some particular properties of the flow and simplifying the duct geometry to find an appropriate wave equation. For instance, the Lilley or Phillip equation can be deduced this way. However, a unique partial differential equation based on the acoustic displacement vector allows a nonhomogeneous flow in an arbitrary duct geometry to be taken into account. This equation was first established by Galbrun in 1931. After recalling the Galbrun equation, a method to solve it is presented. The method uses the Lagrangian properties in order to apply the finite elements method. Different boundary conditions may be introduced. The solution of the Galbrun equation is compared to the solution of the Lilley equation in the case of modal propagation in a lined duct in the presence of a shear flow. Both results are in good agreement, and validate the method used to solve the Galbrun equation.
A unique setting for an opera orchestra
Authors: Wetherill Ewart A.
Published: July 2002

In 1995 the San Francisco Opera vacated the Opera House for one winter season and two summer seasons to allow for substantial renovation necessitated by damage caused during the 1989 earthquake. Rejecting the proposal of canceled opera seasons, the company tackled the more difficult option of utilizing the 4500 seat San Francisco Civic Auditorium augmented by two of San Francisco’s older theaters. The cavernous and noisy Civic Auditorium, which is basically an arena with a large U-shaped balcony, presented a challenge in several dimensions. A complete stage, main floor seating, lighting, and backstage facilities had to be created. Lacking an orchestra pit, the opera designers placed the opera orchestra above dressing rooms, 16 ft above stage level and 60 ft behind the stage apron in a temporary orchestra enclosure. The entire undertaking is seen as a triumph of resourcefulness and willingness to face the challenge of severe physical limitations and budget constraints. Although complicated by an awkward plan configuration and limited overhead access, as well as conflicting rigging for lighting and scenery, the orchestra enclosure nevertheless evolved into a performance element that was both acoustically and visually appropriate. The development of the orchestra enclosure design is discussed in this paper.
Waveguide characterization estimation in shallow water using a vertical array
Authors: Jiang Dejun
Published: July 2002

Waveguide characterization estimation in shallow water using the complex mode approximation of an acoustic field is presented. The advantages of the method are that (1) the dependence on the environmental parameters will obviously decrease. (2) The waveguide characterization parameters (km,βm) can be obtained at the same time, even when the fine structure in the bottom medium, such as the number and thickness of layers, the velocity of compressive and shear wave, and attenuation, is less known or unknown. (3) It can extract the bottom reflection coefficient V(k). Numerical examples illustrate that (1) the accuracy of km is at least 10−5, the related error of βm is mostly less than 20%, and the smaller the mode number, the smaller the related error is. (2) The reflection coefficient in the bottom at low grazing angle can be obtained using a vertical array where the total number of samples is N=18 and the length L=90 m. The experimental data of 500 Hz are emphatically discussed here. The results for an f=500-Hz-wide impulse acoustic signal source which is located at zs=11 m and rs=21 km show that the extracted accuracy of km is between 10−4 and 10−5 and the related error of βm is between 9% and 26%.
Acoustic scattering models of zooplankton from several major anatomical groups—theory and experiment
Authors: Stanton Timothy K. , Chu Dezhang , Wiebe Peter H.
Published: July 2002

In order to estimate zooplankton abundance with active acoustics methods, it is crucial to understand the acoustic scattering properties of the zooplankton. The major challenges in formulating scattering models include the facts that there are no exact solutions for these complex bounded bodies and that the boundary conditions are difficult to determine due to animal size and heterogeneities. A series of laboratory scattering measurements and associated model development has been conducted involving zooplankton from three major anatomical groups: (1) fluidlike (euphausiids), (2) elastic shelled (marine snails, both benthic and pelagic), and (3) gas-bearing (siphonophores). The measurements include backscatter versus acoustic frequency (part or all of the range 24 kHz to 1 MHz) and angle of orientation (up to one-degree precision). Dominant acoustic scattering mechanisms are identified through both spectral and time-domain (pulse compression) analyses and scattering models are developed accordingly. Data and modeling results from the past several years are reviewed and the following new results are presented: (1) a new formulation for predicting scattering at end-on incidence by euphausiids and (2) observations and modeling of a strong peak in scattering levels of the shelled bodies in the upper Rayleigh scattering region. [Work supported by ONR and NSF.]
Perceptual independence of excitor and resonator properties in percussive instrument sounds
Authors: McAdams Stephen , Kudo Koei , Kirchner Holle
Published: July 2002

The perceptual independence of various sensory dimensions has been studied using a speeded classification paradigm developed by Garner. In this paradigm the speed of classification of items varied along one dimension is compared to the same classification when random variation along a second dimension is present. Perceptual interaction is inferred when performance in the latter is slower or worse compared to the former. Such interactions have been shown for simple dimensions such as pitch, loudness, and a spectral dimension of timbre. The present study tested the independence of complex dimensions with overlapping spectral and temporal characteristics. One dimension consisted of the hardness of a percussion mallet (excitor property) and the other of either xylophone bar density or tympani size (resonator properties). These complex source-related dimensions show evidence of interaction in both performance scores and reaction times. A greater independence is found when unrelated variation is introduced along a third dimension (striking force), although performance scores decrease globally. The results are discussed in terms of previously reported interactions among simple dimensions and interactions among complex source properties.
To lend an ear to the dimensionality of space
Authors: Hardy Jean
Published: July 2002

Since the laws of physics are essentially based on our feeling of the real word, it seems natural to consider the problem of the space dimensionality. The usual conception of the space follows from the vision and leads to the conviction that dimensionality of the real word is 3; a similar approach but using the ears is done in this work. An acoustical source emits an impulse in a homogeneous and isotropic N-dimensional space. The Green’s function obtained shows that odd and even dimensionalities have different behaviors. For odd dimensionalities the Green’s function is a combination of a step, a delta function and its derivatives; the step function is responsible for reverberation, the other gives the structure of the impulse front which travels at the wave velocity. The even dimensionality uses the half derivatives for expressing propagation, the wave propagation is subject to reverberation which decreases with the time, the wave velocity is not well defined, and the signal transmission and consequently the communication are difficult if not impossible. An explicit demonstration with 1, 2, 3, 4, and 5 dimensions can be done using musical and speech samples.
Ultrasonic investigation of glass transition dynamics of polyurethane systems
Authors: Baillif Pierre-Yves , Tabellout J. Mohamed , Emery Jacques
Published: July 2002

Ultrasonic technique is an interesting tool to probe high-frequency dynamic properties of materials by determination of the mechanical modulus. Associated with other methods (rheology, DLS, etc.), it allows the investigation of molecular dynamics associated with sol–gel and glass transitions in polymers on a wide frequency range. Polypropylene glycol triol crosslinked with diisocyanate is a good model system for this purpose in polymer networks. By varying the amount of diisocyanate, stable systems are formed which correspond to different stages of polyurethane gel formation. Three triols with different molar masses (260, 700, and 6000 g/mole) are used as precursors in order to apprehend the influence of the macromolecular chain size on the systems dynamics. The temperature dependence of the ultrasonic absorption and velocity shows a relaxation process, the so-called alpha-relaxation associated with the glass transition. The influence of the stoichiometric ratio r=[NCO]/[OH] on this transition is much less important in a large molecular mass precursor system, indicating that entanglement effects become predominant. The ultrasonic relaxation times associated with those obtained by other techniques are represented in an Arrhenius diagram and follow the same William–Landel–Ferry (WLF) law, showing the different systems dynamics’ similarity. The WLF parameters seem, in that case, to have a character of universality.
The generation of low-frequency acoustic waves in electrolytes
Authors: Zoltogorski Bronislaw
Published: July 2002

The phenomenon of the generation of acoustic waves in liquids based on interaction of alternating ion current and constant magnetic field is analyzed. The properties of such a magneto-electric transducer having no mechanical vibrating elements is examined theoretically (with the use of an electric equivalent circuit) and experimentally. The following measurements were carried out: (1) amplitude of conductivity current as a function of frequency, (2) amplitude of acoustic pressure at the distance of 0.5 m without constant magnetic field and (3) with magnetic field. For water from a municipal water-pipe network, the upper limit frequency of the current characteristic is 4 to 5 kHz. The same frequency properties exhibit a pressure characteristic. The directional pattern of the source depends on the shape of the electrodes and can be optimized for special aims. The energetic efficiency of the transducer is not great because the majority of the electric power is converted into heat and causes an increase in temperature of the liquid. That process is relative to a big value of resistance of weak electrolytes. That type of transducer can be applied in liquids without ion conductivity by submerging a container with very thin rubber walls and with mounted electrodes and filling with an electrolyte.
Acoustic nonlinearity calculations using the Tait equation of state
Authors: Hartmann Bruce , Lee Gilbert F. , Balizer Edward
Published: July 2002

Beyer’s B/A parameter of acoustic nonlinearity was calculated using the Tait equation of state supplemented with specific heat results, in the same manner as done earlier with our equation of state [J. Acoust. Soc. Am. 82, 614 (1987)]. Calculations were made of sound speed, sound-speed temperature and pressure derivatives, the two components of B/A, and the value of B/A for a series of six n-alkane liquids as well as the limiting case of molten polyethylene. All these results were compared with experimental data from the literature. In addition, a comparison of the results with Ballou’s rule (linear relation of B/A versus reciprocal sound speed) was made. Overall, values calculated using the Tait equation are found to agree with experiment about as well as our equation of state, though the pressure derivatives of the sound speed and the final value of B/A are generally not as accurate using the Tait equation. [Work supported by the Naval Surface Warfare Center’s In-house Laboratory Independent Research Program.]
Acoustical nonlinearity and its images in biomedicine
Authors: Gong X. F. , Zhang D. , Ye S. G. , Liu X. Z. , Chen X. , Zhang W. Y.
Published: July 2002

Some acoustical nonlinear effects in biological media at medical ultrasonic frequencies and intensities were studied experimentally. These phenomena include wave distortion, harmonic generation, energy transformation, extra-attenuation, departure of intensity response curve from linear relation, etc. The influence of these effects on medical ultrasonic diagnosis and therapy was discussed. As a basic parameter in nonlinear acoustics, the acoustical nonlinearity parameter can describe the above-mentioned nonlinear effects and provide some information on the structure and composition of biological tissues. Thus the imaging method of an acoustical nonlinearity parameter using secondary wave detection was developed and investigated. Nonlinearity parameter tomography for normal and a series of pathological porcine tissues was presented. The results obtained in experiments indicate that the difference between normal and diseased tissue in nonlinearity parameter tomography is more sensitive than that in linear parameter tomography. Therefore, nonlinearity parameter tomography may become a novel imaging method for tissue characterization. [Work supported by NSF of China.]
Modeling spectral integration in binaural signal detection
Authors: Breebaart Jeroen , van de Par Steven , Kohlrausch Armin
Published: July 2002

Estimates of critical bandwidths in binaural experiments vary considerably across experimental conditions. For masking experiments using signals of varying bandwidths (i.e., spectral integration), and experiments with a frequency-dependent interaural masker correlation, bandwidth estimates agree with those from monaural experiments. However, if auditory bandwidths are estimated from binaural band-widening masking experiments, the effective bandwidth is usually a factor of 2 to 3 times larger than monaural estimates. One often ignored detail is that this difference between monaural and binaural estimates decreases with decreasing masker level [Hall et al., J. Acoust. Soc. Am. 73, 894–898 (1983)]. Using the binaural model described by Breebaart et al., we have simulated the binaural experiments described above. It can be shown that, without any parameter change in the model, basically all relevant conditions can be modeled accurately, including the band-widening and spectral integration experiments. In agreement with the scheme discussed by Kohlrausch et al., detection in binaural narrow-band-noise conditions is improved by analyzing the internal representation in several adjacent filters. It is concluded that the absence of this detection advantage in monaural random-noise conditions is the primary cause for the so-called ‘‘wider binaural critical band.’’
The role of the head related transfer function low-frequency component for sound localization on a median plane
Authors: Yairi Motoki , Kuroki Yasuko , Morimoto Masayuki , Iida Kazuhiro
Published: July 2002

Asano et al. [J. Acoust. Soc. Am. 88, 159–168 (1990)] demonstrated that localization is not accurate for the simulation of sound sources on the median plane when the low-frequency component of head related transfer functions (HRTFs) are smoothed. In the present localization experiment, the low- and high-frequency components of white-noise stimuli were separated at fc=4.8 kHz (−48 dB/oct.). Those components were independently presented from different directions. Results show that the sound image is localized in the direction from which the high-frequency component is presented, regardless of the direction of low-frequency component, showing that the low-frequency component has no evident effect on the sound localization on a median plane. Based on the results of these two experiments, it is concluded that only the high-frequency component of an HRTF provides spectral cues for sound localization on a median plane. However, changing the low-frequency component of the HRTF, which is unlikely to naturally occur in sound localization on a median plane, may interfere with accurate localization.
Evidence of spatially tuned auditory analyzers
Authors: Martin Russell L. , Klimkeit Ester
Published: July 2002

The primary-plus-probe uncertainty technique was used to explore the possibility that analyzers tuned to different spatial locations exist within the human auditory system. Eight subjects’ psychometric functions for detection of a 500-Hz tone when presented from a speaker located at 0 and 90 degrees azimuth were measured in each of two conditions. In the first, the intermixed condition, subjects knew that 80% of signals would be presented from one location (the primary location) and 20% would be presented from the other (the probe location). In the second, subjects knew that all signals would be presented from either the primary or probe location. For each subject the primary location was 0 degrees for half the sessions and 90 degrees for the others. Each function was measured using a two-interval forced-choice task and five signal levels ranging from 7.5 dB above to 4.5 dB below the subject’s previously estimated threshold. For primary location signals, average functions for the two conditions were indistinguishable. For probe location signals, however, functions differed, reflecting significantly poorer detection performance in the intermixed condition [F(1,7)=3D22.38, p<0.01]. This uncertainty effect provides support for the notion that spatially tuned analyzers exist within the auditory system.
Measurement and analysis of the structure-borne sound of a fan installation: Evaluation of source signal filtering techniques and rotational degrees of freedom
Authors: Sanderson Michael A. , Ivarsson Lars , Troshin Andrej G.
Published: July 2002

The structure-borne sound characteristics of a commonly found fan installation were examined through measurements and further analyses in the frequency range up to 500 Hz. The focus was to determine the prediction improvements by including the rotational degrees of freedom. Free velocities of the fan were measured in five degrees of freedom (in-plane rotation or twisting motion were neglected), while fan mobilities were measured and foundation mobilities were predicted in three degrees of freedom: a translational and two rotational, those resulting in bending motion. The two in-plane translations were considered by transforming their motion to rotations resulting in moment excitations on the foundation. Measurements were also made of the corresponding isolators’ stiffness values. Comparisons are made with power measurements of the complete system. It was found that an unsatisfactory moment excitation resulted in one of the rotational degrees of freedom while employing a twin shaker arrangement when determining the fans’ mobilities. Therefore, a source signal filtering technique was applied to improve the measurement. Comparisons are made with the originally measured mobilities. [This work has been supported by the Swedish Council for Building Research (BFR) through Contract 950192-8 and the Swedish Research Council for Engineering Sciences (TFR) through Contract 95-160.]
Experimental identification of mechanical joint dynamic properties
Authors: Chiello Olivier , Sgard Franck C. , Atalla Noureddine
Published: July 2002

Large structures are often composed of substructures connected through mechanical joints. The dynamic behavior of these joints is generally difficult to characterize. In this paper, a method for identifying dynamic joint characteristics is presented. Joint properties are extracted directly from measured frequency responses of the assembled structure. Measurement points are not taken on the interface between the structure components. This feature is of practical importance since it is often difficult to directly attach a transducer on the joint. The method only requires the knowledge of the frequency responses of the substructures taken separately. These responses can be either measured, analytically calculated, or simulated by FEM. The presented approach allows for the determination of the joint properties as a function of frequency. The joint properties extracted from one assembled structure can be used to predict the behavior of another structure assembled with the same joint condition. The applicability of the proposed method is investigated by numerical simulations. Errors in simulated frequency responses are introduced to investigate the robustness of the method. It is shown that the accuracy of the identified results is good.
Acoustic and perceptual effects of vowel length on voice onset time in Thai stops
Authors: Onsuwan Chutamanee , Beddor Patrice S.
Published: July 2002

In Thai, vowel length (e.g., [pan]-[paan]) and unaspirated–aspirated stop (e.g., [pan]-[phan]) distinctions are contrastive; this study examines possible acoustic and perceptual interactions between these temporal properties. VOT and vowel duration were measured for five repetitions of 40 (near-) minimal word pairs beginning with aspirated or unaspirated bilabial, alveolar, or velar stops followed by long or short vowels, produced by three native Thai speakers. Although VOT for velars was slightly longer (about 5 ms) before long than before short vowels, the overall acoustic picture across places of articulation showed no systematic effect of vowel length. To test for perceptual influences of contrastive vowel length on VOT, a 15-step 0–90 ms VOT continuum was created by editing the aspiration portion of naturally produced [phaan]. The VOT continuum was spliced onto the vowel portion of four different natural tokens, [pan], [paan], [phan], and [phaan], creating four continua, two with long vowels and two with short. Identification tests were presented to 18 native Thai listeners. Responses to the continua created from the originally unaspirated tokens ([pan], [paan]) showed robust effects of vowel length: the long vowel continuum elicited more aspirated ([ph]) responses. A compensatory account of the perceptual findings is offered. [Work supported by NSF.]
The nasal vowels of Iberian Portuguese
Authors: Galvao Maria Joao C.
Published: July 2002

Previous analysis [Mateus, ‘‘Aspectos da Fonologia Portuguesa’’ (1982)] of Iberian Portuguese nasal vowels has suggested that there are three degrees of nasality, predictable from syllable structure and from the presence or absence of an underlying nasal consonant following the nasal vowel. This study addresses the question of whether vowel quality affects the degree of phonetic nasality in Portuguese. Nasalance measurements of seven native speakers of Portuguese were obtained via a Kay Nasometer 6200, while spectrographic analysis was provided by a Kay CSL 4300B. The present analysis confirms that a trace of the nasal consonant is phonetically present which provides a peak target for the nasal vowel, but the degree of nasality of the vowel itself is solely determined by vowel height: as occurs in other languages with nasal vowels, high vowels have a more constricted oral air passage and hence higher nasalance percentage.
EMG evidence for the automaticity of intrinsic F0 of vowels
Authors: Whalen D. H. , Gick Bryan , Kumada Masanobu , Honda Kiyoshi
Published: July 2002

Although vowels can be produced with many F0 values, high vowels’ F0s tend to be higher than low vowels’, a tendency found for every language examined. Nonetheless, this ‘‘intrinsic F0’’ (or IF0) has been called a deliberate ‘‘enhancement’’ of the speech signal, aiding vowel height perception. Since IF0 remains constant with the number of vowels in a language, this enhancement seems unlikely. The only positive evidence for it is that activity of the cricothyroid (CT) muscle, which primarily raises F0, is larger for high vowels than for low. The present experiment explores this by having subjects produce vowels at slightly different F0s, with the differences being similar to the IF0 magnitude for each subject. The first subject (of four planned) showed no vowel height difference in CT; further, an analysis factoring out F0 as a covariate showed that high vowels had higher CT activation. Thus different vowels involve different levels of CT activity for a given F0; previous findings were likely due not to F0 control but to F0/vowel quality interactions. Even the EMG evidence, then, renders IF0 an unlikely speech enhancement. Rather, IF0 appears to be an automatic consequence of vowel production. [Supported by NIH Grant DC-02717.]
The organization of articulator gestures: A comparison of Swedish, Bulgarian, and Greenlandic
Authors: Wood Sidney A. J.
Published: July 2002

This paper reports speech articulator gestures in Swedish, Bulgarian, and Greenlandic to study universal and language-specific components in articulation. This work is based on analysis of movements of individual articulators from x-ray motion films of speech, and continues from previous reports from this study by Wood [J. Phon. 7, 25–43 (1979); 19, 281–292 (1991); Proc. 3rd Conf. I.C.P.L.A., 191–200, Helsinki (1994); Proc. 13th I.C.Ph.S. Vol. 1, 392–395, Stockholm (1995); J. Phon. 24, 139–164 (1996); Proc. 4th Speech Prod. Sem., 61–64, Grenoble (1996); Speech Commun., (in press)], and by Wood and Pettersson [Folia Ling. 22, 239–262 (1988)]. Common principles concerned utilization and integration of articulator gestures (articulator gestures executed in approach, hold, and withdrawal phases, four tongue body gestures used, all gestures available for vowels and consonants, gesture conflicts resolved by gesture queuing, coarticulation and assimilations implemented by coproduction). Language-specific principles concerned implementation of assimilations like palatalization of alveolar stops in Bulgarian and uvularization of vowels in Greenlandic. One assimilation, palatalization of velar consonants, is common to all three languages. A model of gesture programming based on these results is proposed.
A comparison of the finite-difference time-domain and integral equation methods for scattering from shallow water sediment bottoms
Authors: Hastings Frank D. , Schneider John B. , Broschat Shira L. , Thorsos Eric I.
Published: July 2002

Scattering from sediment bottoms has a significant effect on acoustic propagation in shallow water. When shear effects are negligible, the water–sediment interface can be modeled using a fluid–fluid model. In this paper, finite-difference time-domain (FDTD) and integral equation (IE) results are compared for a fluid–fluid rough interface. Both methods are exact in that they make no physical approximations, and both can be used either to benchmark approximate analytical methods or to study the propagation problem directly. The comparison presented verifies the numerical accuracy of the two methods. Scattering strengths are computed using a Monte Carlo average over a set of 50 surfaces. Results for single surface realizations are presented as well. Both single-scale Gaussian and multiscale modified power law (MPL) roughness spectra results are presented. While the MPL spectrum is more realistic for shallow water problems, the Gaussian spectrum gives low scattering levels in the backscatter direction, permitting a stringent test of numerical accuracy. Several different bottom types are considered for which the shear speeds are negligible, and attenuation has not been included. For all cases, the FDTD and IE results are obtained using the same surface realizations. In general, the results agree well. [Work supported by ONR.]
Sediment density heterogeneity spectra estimated from digital X-radiographs
Authors: Tang Dajun , Wheatcroft Robert A.
Published: July 2002

It has been confirmed that sediment volume heterogeneity is one of the major bottom scattering mechanisms, especially in soft-sediment areas. In most cases, scattering by sediment heterogeneity can be modeled by a first-order perturbations technique. The crucial input to such models is the spectrum of sediment spatial heterogeneity. It is difficult to obtain reliable data to estimate such spectra, however, because (1) two-dimensional data sets collected from statistically similar sites are needed, and (2) the data need to cover several orders of magnitude in spatial dimensions. Digital X-radiographs of sediment cores provide an ideal form of data for estimating the spectrum of sub-bottom density variability. Here the data processing procedures will be provided in detail, and physical insights into the resultant spectra discussed. Last, bistatic scattering coefficients resulting from these spectra will be presented.
Recent observations of high-frequency acoustic wave propagation in the Delaware Bay
Authors: Badiey M. , Forsythe S. , Simmen J. , Tang X.
Published: July 2002

Broadband acoustic propagation measurements, as well as complementary environmental measurements including CTD, ADCP, and wind speed, have been conducted in the Delaware Bay during March and September, 1997. With the data from these complete experiments, acoustic pulse travel time and intensity are related to the sound-speed fluctuations in the water column, the sea-surface profile, and the bottom roughness. The direct arrival between acoustic source and receiver contains information about ocean current and temperature, while the arrival corresponding to a single surface bounce contains additional information about the sea-surface roughness. Independent measurements of temperature and current allow the sorting of acoustic fluctuations due to ocean volume fluctuations from those due to sea-surface fluctuations. Coherence of the broadband acoustic signals is calculated from the observed data and is found to be correlated with the environmental parameters.
Effect of electrical outlet boxes on sound insulation of a cavity wall
Authors: Nightingale T. R. T. , Quirt J. D.
Published: July 2002

The results of a systematic study investigating the effect on the sound insulation of wood stud walls having penetrations made by electrical outlet boxes are presented. The effect on sound insulation is shown to be almost negligible, regardless of box separation, if the boxes are themselves airtight and form an airtight seal with the gypsum board surfaces. However, if the boxes are not airtight, then the degradation to the sound insulation is strongly dependent on the separation between the boxes. Other significant factors include the presence of cavity absorption, and its method of installation. A series of retrofits for poorly installed boxes is examined and show that commonly available devices for reducing airflow (and sound insulation) through electrical boxes can be very effective but are highly dependent on installation.