bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of temporal changes of mammographic features: Computer‐aided classification of malignant and benign breast masses
Authors: Hadjiiski Lubomir , Sahiner Berkman , Chan Heang‐Ping , Petrick Nicholas , Helvie Mark A. , Gurcan Metin
Published: July 2002

A new classification scheme was developed to classify mammographic masses as malignant and benign by using interval change information. The masses on both the current and the prior mammograms were automatically segmented using an active contour method. From each mass, 20 run length statistics (RLS) texture features, 3 speculation features, and 12 morphological features were extracted. Additionally, 20 difference RLS features were obtained by subtracting the prior RLS features from the corresponding current RLS features. The feature space consisted of the current RLS features, the difference RLS features, the current and prior speculation features, and the current and prior mass sizes. Stepwise feature selection and linear discriminant analysis classification were used to select and merge the most useful features. A leave‐one‐case‐out resampling scheme was used to train and test the classifier using 140 temporal image pairs (85 malignant, 55 benign) obtained from 57 biopsy‐proven masses (33 malignant, 24 benign) in 56 patients. An average of 10 features were selected from the 56 training subsets: 4 difference RLS features, 4 RLS features, and 1 speculation feature from the current image, and 1 speculation feature from the prior, were most often chosen. The classifier achieved an average training of 0.92 and a test of 0.88. For comparison, a classifier was trained and tested using features extracted from the 120 current single images. This classifier achieved an average training of 0.90 and a test of 0.82. The information on the prior image significantly improved the accuracy for classification of the masses.
The influence of angular misalignment on fixed‐portal intensity modulated radiation therapy
Authors: Low Daniel A. , Zhu Xiao Rong , Purdy James A. , Söderström Svante
Published: July 2002

A method has been developed to estimate potential dose errors due to linear accelerator angular setting misalignments of Intensity Modulated Radiation Therapy (IMRT) treatments. A first‐order approximation to the dose error at a point is modeled as the dot product of the dose gradient and the shift vector of the point due to the rotational error. The analysis method is applied to a previously published set of optimized fluences for a 50 MV IMRT pelvis irradiation. Three of the published cases exhibiting a wide range of modulation are presented; a rectangular open field, a field optimized for a static multileaf collimator defining the portal outline coupled with a single broad bremsstrahlung profile modulation, and a fully modulated field using a physical modulator. To examine the energy dependence of angle setting errors, the study is repeated using the same fluence distributions, but with a dose‐spread kernel appropriate for a 6 MV photon beam. The collimator angle error is set to 2°, and the dose error determined with both a centrally located isocenter and an isocenter chosen to model a split‐field geometry. The dose error due to a 2° gantry setting error is assessed at a plane 10 cm distal to the isocenter. The mathematical form of the dose error due to couch motion is similar to the other two errors, so the dose error resulting from a couch angle missetting is not presented. The magnitude of the errors is largest for the 6 MV beam, while the volume encompassed by the errors is greater for the 50 MV beam. The gantry error yields the largest dose error values, with the 6 MV modulated case presenting dose errors of greater than 40%.
Reporting and analyzing dose distributions: A concept of equivalent uniform dose
Authors: Niemierko Andrzej
Published: July 2002

Modern treatment planning systems for three‐dimensional treatment planning provide three‐dimensionally accurate dose distributions for each individual patient. These data open up new possibilities for more precise reporting and analysis of doses actually delivered to irradiated organs and volumes of interest. A new method of summarizing and reporting inhomogeneous dose distributions is reported here. The concept of equivalent uniform dose (EUD) assumes that any two dose distributions are equivalent if they cause the same radiobiological effect. In this paper the EUD concept for tumors is presented, for which the probability of local control is assumed to be determined by the expected number of surviving clonogens, according to Poisson statistics. The EUD can be calculated directly from the dose calculation points or, from the corresponding dose‐volume distributions (histograms). The fraction of clonogens surviving a dose of 2 Gy (SF2) is chosen to be the primary operational parameter characterizing radiosensitivity of clonogens. The application of the EUD concept is demonstrated on a clinical dataset. The causes of flattening of the observed dose‐response curves become apparent since the EUD concept reveals the finer structure of the analyzed group of patients in respect to the irradiated volumes and doses actually received. Extensions of the basic EUD concept to include nonuniform density of clonogens, dose per fraction effects, repopulation of clonogens, and inhomogeneity of patient population are discussed and compared with the basic formula.
Feasibility of a large area x‐ray sensitive vidicon for medical fluoroscopy: Resolution and lag factors
Authors: Luhta R. , Rowlands J. A.
Published: July 2002

A large area x‐ray‐sensitive vidicon utilizing amorphous selenium is being investigated as an alternative to the x‐ray image intensifier and television camera combination (XRII/TV) for medical fluoroscopy. The x‐ray vidicon is, to a first approximation, a scaled up version of the 1″ (2.54 cm) light‐sensitive vidicon. The modulation transfer function (MTF) of an x‐ray vidicon is mainly determined by the number of lines used, the beam spot profile, and the electronic bandwidth. The x‐ray vidicon is expected to have roughly the same MTF as the 1″ vidicon from a XRII/TV system referenced to the x‐ray input and as such will be superior to the MTF of the complete XRII/TV system especially in high resolution applications such as cardiac cine. Beam discharge lag is expected to be approximately the same as in the 1″ vidicon since they have comparable photoconductor layer capacitance. Photoconductive lag is also expected to be low since ‐Se is known to have a low trap density.
Dual‐energy bone densitometry using a single 100 ns x‐ray pulse
Authors: Seely John F. , Boyer Craig N. , Holland Glenn E.
Published: July 2002

A pulsed, portable hard x‐ray source has been developed for medical imaging and flash x‐ray absorptiometry. The source is powered by a Marx generator that drives a field emission x‐ray tube which produces a 30–300 keV x‐ray pulse of 100 ns duration. The x‐ray fluence has dual‐energy properties. The x‐ray energy is relatively high early in the pulse and lower later in the pulse. The feasibility of using a single x‐ray pulse for precision bone densitometry was analyzed. A computer simulation model was developed for the x‐ray source, the filtration that enhances the dual‐energy distribution, the absorption of the energy distribution by bone mineral and soft tissue, and the dual‐energy detection system. It is feasible to determine the bone mineral density (BMD) of axial sites such as the lumbar spine and proximal femur with 2% precision over an area that is 15–20 mm in size, depending on the bone mineral and soft tissue thicknesses. An algorithm for determining the absolute BMD, to an accuracy of 2%, using a Plexiglas™/ calibration phantom is discussed. At a distance of 50 cm from the source, the patient exposure is 3.7 mR. The average absorbed bone and tissue doses are 0.6 and 4.3 mrem, respectively. Factors that facilitate diagnostic measurements in clinical settings are the short patient observation time and the portability of the x‐ray source.
The quantum mechanical current of the Pauli equation
Authors: Nowakowski Marek
Published: July 2002

We argue that the process of constructing the quantum mechanical current of the Pauli equation by copying the line of argument used in the spin-0 case, i.e., the Schrödinger equation, is ambiguous. We show that a nonrelativistic reduction of the relativistic Dirac four-vector current is, however, capable of fully resolving the problem. This analysis reveals that the nonrelativistic current of the Pauli equation should include an extra term of the form ∇×(ψ†σψ). We present an initial exploration of the potential consequences of this new “spin term” by solving the Pauli equation for crossed magnetic and electric fields and calculating the corresponding current.
Computers in teaching science: To simulate or not to simulate?
Authors: Steinberg Richard N.
Published: July 2002

Do computer simulations help students learn science? How can we tell? Are there negative implications of using simulations to teach students about real world phenomena? In this paper I describe my experience using a computer simulation on air resistance. In order to parse out the effects of using the computer simulation and of having an interactive learning environment, I compare two classes which both had interactive learning environments. One class used the simulation and the other class used only a set of paper and pencil activities. In the two different learning environments, there appears to be differences in how students approached learning. However, student performance on a common exam question on air resistance was not significantly different.
Physical limitations of travel-time-based shallow water tomography
Authors: Rodrı́guez Orlando C. , Jesus Sérgio M.
Published: July 2002

Travel-time-based tomography is a classical method for inverting sound-speed perturbations in an arbitrary environment. A linearization procedure enables relating travel-time perturbations to sound-speed perturbations through a kernel matrix. Thus travel-time-based tomography essentially relies on the inversion of the kernel matrix and is commonly called “linear inversion.” In practice, its spatial resolution is limited by the number of resolved and independent arrivals, which is a basic linear algebra requirement for linear inversion performance. Physically, arrival independency is much more difficult to determine since it is closely related to the sound propagating channel characteristics. This paper presents a brief review of linear inversion and shows that, in deep water, the number of resolved arrivals is equal to the number of independent arrivals, while in shallow water the number of independent arrivals can be much smaller than the number of resolved arrivals. This implies that in shallow water there are physical limitations to the number of independent travel times. Furthermore, those limitations are explained through the analysis of an equivalent environment with a constant sound speed. The results of this paper are of central importance for the understanding of travel-time-based shallow water tomography.
Acoustic scattering by internal solitary waves in the Strait of Gibraltar
Authors: Tiemann Christopher O. , Worcester Peter F. , Cornuelle Bruce D.
Published: July 2002

High-frequency underwater acoustic transmissions across the Strait of Gibraltar were used to examine acoustic scattering caused by the unique internal wave field in the Strait. Internal solitary waves of 100 m in amplitude propagate along the interface between an upper layer of Atlantic water and a lower layer of Mediterranean water. The interface is also strongly modulated by internal tides of comparable amplitude. As internal solitary waves cross the acoustic path, they cause sharp soundspeed gradients which intermittently refract acoustic rays away from normal sound channels. Internal tides vertically shift soundspeed profiles for additional travel time variability. Although the acoustic scattering is quite complicated, it is also surprisingly robust, making it a good candidate for modeling. Key features of the acoustic arrival pattern can be accounted for in some detail by a model description of the complex hydraulics in the Strait.
On the theory of acoustic flow measurement
Authors: Wendoloski J. C.
Published: July 2002

The motivation for this paper arises from problems frequently encountered in acoustic flow measurement. Of primary concern is that acoustic flow meters, rather than directly measuring the volume flow rate, measure some biased average of fluid velocity in a duct. That is, the average is usually not equal to the volume flow rate divided by the duct cross-sectional area, and is influenced by alterations in the flow profile. In this paper perturbation analysis is used to characterize nontrivial situations under which a sound field may be convected to first order by the unbiased cross-sectionally averaged flow. Perturbation analysis previous to this paper has considered only the plane-wave approach to the problem. This paper will examine the use of higher-order duct modes. It will be shown that under certain circumstances these modes are less prone to distortion by the flow field than the plane wave, and will still average the flow to an approximation which improves with mode order. The study is restricted to the consideration of rectangular section ducts and cylindrical ducts with axisymmetric flow fields. As an aside, the two-dimensional viscous convective wave equation by Mungur and Gladwell [J. Sound Vib. 9, 28–48 (1969)], has been extended to three dimensions in this paper. In deriving this form it was noticed that an error existed in the original equation. This error has been corrected in the present three-dimensional version of the equation.
Mode counts in an aluminum foam
Authors: Lobkis Oleg I. , Weaver Richard L.
Published: July 2002

Measurements of the ultrasonic modal density of a disordered elastic frame, a 20 pore-per-inch open-celled aluminum foam, are reported. While the material is dissipative, with a Q only around 700, sufficiently careful signal processing has allowed reliable counts of the modes up through a few hundred, corresponding to wavelengths comparable to the strut lengths. The modal density is found to be essentially constant over this range, and to bear no resemblance to theoretical estimates based on long-wavelength effective moduli.
Detecting stop consonants in continuous speech
Authors: Niyogi P. , Sondhi M. M.
Published: July 2002

The problem of implementing a detector for stop consonants in continuously spoken speech is considered. The problem is posed as one of finding an optimal filter (linear or nonlinear) that operates on a particular appropriately chosen representation, and ideally outputs a 1 when a stop occurs and 0 otherwise. The performance of several variants of a canonical stop detector is discussed and its implications for human and machine speech recognition is considered.
The use of a combination frequency technique to measure the surf zone bubble population
Authors: Phelps Andy D. , Ramble David G. , Leighton Timothy G.
Published: July 2002

There are great benefits to sizing bubbles using a two frequency technique, which examines the appearance of sum-and-difference signals generated by the interaction between a resonant bubble pulsation and a much higher frequency imaging beam. This paper presents the results from using the technique to size bubbles in the ocean surf zone, and details the pulsation model used to calibrate the returned data such that the height of the bubble scattered signal can be related to the number of resonant bubbles of that size. It also shows how ambiguities and inaccuracies (brought on through turbulence and the substantial off-resonance nature of the signal) which affected earlier oceanic tests using the same method can be identified in the returned signal or removed from the estimate during the data processing.
Linearized response growth inferred from growth-of-masking slopes in ears with cochlear hearing loss
Authors: Nelson David A. , Schroder Anna C.
Published: July 2002

Growth of masking for OFF-frequency conditions (probe frequency above the masker spectrum) and ON-frequency conditions (probe within the masker spectrum) was investigated using simultaneous masking in three subjects with normal hearing and nine subjects with high-frequency sensorineural hearing loss. Growth-of-masking functions (probe thresholds as a function of masker intensity) for OFF-frequency conditions were obtained for probe tones placed at six frequencies above a 200-Hz-wide masker with an upper edge at 520 Hz. Growth-of-masking functions for ON-frequency conditions were obtained for probe tones placed within the 200-Hz-wide masker and for probe tones placed within 400-Hz-wide maskers with upper edges at 1040, 1300, 1627, and 2040 Hz (probe tones placed 20 Hz below the upper edge frequency). Growth-of-masking functions were fit with a power function of masker intensity added to an internal noise with intensity equal to the absolute threshold for the probe, and were well described by two free parameters and a threshold constant: the growth-of-masking slope (β), a masking sensitivity constant (κ) that indicated the minimum effective masker level at which masking began, and the intensity of the probe at absolute threshold (IT). For OFF-frequency masking conditions, growth-of-masking slopes (β) decreased by a factor of 0.8 for every 10 dB of hearing loss. Comparisons with data from previous studies of upward spread of masking, and assumptions about underlying physiological mechanisms, led to the conclusion that more gradual than normal growth-of-masking slopes reflect larger (steeper) growth-of-response slopes at the probe frequency in regions of hearing loss. Derived response-growth exponents increased by a factor of 1.2 for every 10 dB of hearing loss (HL), from an exponent around 0.25 at 0 dB HL to an exponent around 1.0 at 75 dB HL (linear response growth). Masking sensitivity constants (κ), the minimum effective masker levels, indicated that masking began at slightly higher masker levels in subjects with sensorineural hearing loss than in subjects with normal hearing. It was concluded that higher masked thresholds in regions of hearing loss were due primarily to a loss of active gain at the probe frequency and were not due to an excessive response at the probe frequency to the lower-frequency masker. For ON-frequency masking conditions, growth-of-masking slopes were not different from normal in hearing-impaired subjects. ON-frequency masking began when the effective power within an auditory filter at the probe frequency reached elevated absolute threshold at the probe frequency. Critical ratios were normal except for one subject with the most hearing loss.
Further studies of phonation threshold pressure in a physical model of the vocal fold mucosa
Authors: Chan Roger W. , Titze Ingo R. , Titze Michael R.
Published: July 2002

This paper reports results of further experimentation on a previously developed physical model of the vocal-fold mucosa [Titze et al., J. Acoust. Soc. Am. 97, 3080–3084 (1995)]. The effects of vocal-fold thickness, epithelial membrane thickness, and prephonatory glottal geometry on phonation threshold pressure were studied. Phonation threshold pressures in the range of 0.13 to 0.34 kPa were observed for an 11-mm-thick vocal fold with a 70-μm-thick “epithelial” membrane for different “mucosal” fluid viscosities. Higher threshold pressure was always obtained for thinner vocal folds and thicker membranes. In another set of experiments, lowest offset threshold pressure was obtained for a rectangular or a near-rectangular prephonatory glottis (with a glottal convergence angle within about ±3°). It ranged from 0.07 to 0.23 kPa for different glottal half-widths between 2.0 and 6.0 mm. The threshold for more convergent or divergent glottal geometries was consistently higher. This finding only partially agrees with previous analytical work which predicts a lowest threshold for a divergent glottis. The discrepancy between theory and data is likely to be associated with flow separation from a divergent glottis.
Modal impulse response and wave vector–time domain methods to evaluate transient radiation from axisymmetric planar radiators
Authors: Sun Jie , Stepanishen Peter R.
Published: July 2002

The modal impulse response method and the wave vector–time domain method are two of the existing methods to evaluate the transient acoustic field from an axisymmetric planar radiator. Both methods are investigated here and the wave vector–time domain method is used to derive the modal impulse response for the normal velocity distribution of an arbitrary axisymmetric source. Representations of the transient acoustic field in the space–time domain and the wave vector–time domain are linked through the Fourier–Hankel transform. A piston is first addressed as a result of its simplicity which serves as a benchmark case; a Bessel shaded aperture is then addressed as a result of its importance. Clearly, the piston case is a special case of the spatial Bessel shading cases. Numerical results are presented for both cases to illustrate the procedures in using the modal impulse response and the wave vector–time domain methods.
Effects of high-sided vehicles on the performance of noise barriers
Authors: Hothersall D. C. , Tomlinson S. A.
Published: July 2002

The attenuation produced by a given barrier can be maximized by placing it as close to the noise source or receiver as possible. This fact and the availability of land often means that barriers are situated close to the edge of the road. In this position the performance of the barrier can be degraded by the effects of multiple reflections of sound between the sides of the vehicles and the barrier. This paper reports the results of calculations, carried out using a two-dimensional boundary element model, of the attenuation produced by various configurations of barrier adjacent to a traffic stream. Spectra of insertion loss and the mean broadband insertion loss in the shadow region are considered. The effects of the height of the vehicle, the distribution of absorbing material on the traffic-facing side of the barrier, and the slope of this face are considered quantitatively in terms of the peak noise level. It is concluded that serious degradation of the performance of the barrier can occur for some situations, especially when the side of the vehicle protrudes above the barrier. The results indicate the extent to which the problem can be overcome by the use of absorbing barriers or by sloping barriers of suitable design.
Autophasing of free volume oscillations of air cavities in water
Authors: Bredikhin V. V. , Kobelev Yu. A. , Vasilinenko N. I.
Published: July 2002

This paper deals with theoretical and experimental investigations on free oscillations of air cavities formed in a metal plate lying on a water surface. The cavity is both an oscillator produced by the air elasticity in combination with the water mass, and a source of sound. Unlike gas bubbles in water, a cavity allows one to control the cubic nonlinearity coefficient up to a change of sign and to excite free oscillations rather easily. Measurements of the eigenfrequencies, damping factor, and the cubic nonlinearity coefficient of oscillations, taken for a variety of cavity volumes, are reported. Two- and three-cavity systems have been investigated to determine the eigenfrequencies of oscillations of the monopole and dipole modes. For the first time, the effect of autophasing of oscillations generated by ensembles of two and of three oscillators involved in a linear interaction via the near field was observed. The energy of the dipole oscillations of the system was transferred in this process to the monopole oscillations that effectively radiated acoustic waves. A possibility is discussed of using such oscillators as active elements for acoustic masers.
Regularized matched-mode processing
Authors: Collison Nicole E. , Dosso Stan E.
Published: July 2002

Far-field acoustic propagation can be modeled as a discrete set of propagating normal modes. In this case, the measured fields can be decomposed into their modal components, providing the basis for matched-mode processing (MMP). Modal decomposition is a discrete linear inverse problem that is inherently nonunique and can be unstable. Thus standard MMP generally requires the entire water column to be densely sampled (i.e., more sensors than modes) with relatively low noise. However, the inversion can be stabilized using the method of regularization to include a priori information based on the replica excitations at each trial source location of the search grid. The regularized approach gives an optimal match for each grid point for both dense and sparse arrays and noisy data. Regularized matched-mode processing (RMMP), MMP, and matched-field processing (MFP) are compared for a number of different array configurations, including dense and sparse arrays that span all or part of the water column. The comparison is carried out for a realistic shallow-water environment which includes elastic geoacoustic properties and an environmental noise model. [For Underwater Acoustics Best Student Paper Award.]
Sensitivity of acoustic scattering models to fish morphometry
Authors: Jech J. Michael , Horne John K.
Published: July 2002

Current efforst to model fish backscatter (e.g., Kirchoff ray-mode model [C. S. Clay and J. K. Horne, J. Acoust. Soc. Am. 96, 1661–1668 (1994)] use digitized images of fish anatomy for a more realistic representation of swimbladder shape, volume, and aspect. However, the degree of image resolution necessary for acoustic characterization and improved predictions, and the variability associated with resolution has not been quantified. Does a more accurate and higher resolution image result in improved correlation between theory and empirical measurements? Backscatter amplitudes display strong relationships with carrier frequency, swimbladder shape, and swimbladder aspect at rather high frequencies. Are predictions of these relationships influenced by image resolution? X-ray images of Atlantic cod (Gadus morhua) and brook trout (Salvelinus fontinalis) were digitized at fine resolution, and sensitivity analyses were performed to quantify the effect of varying image resolution on predicted backscatter as a function of carrier frequency and swimbladder shape and aspect. Quantifying image resolution is a step towards determining morphometric effects on backscatter variability and estimating fish abundance using multi-frequency data and the inverse approach. [Work supported by ONR.]
Temporal properties of loudness recalibration
Authors: Mapes-Riordan Dan , Yost William A.
Published: July 2002

Loudness recalibration occurs when a loud (recalibration) tone at frequency f1 precedes quieter test tones at frequencies f1 and f2. Recalibration is a reduction in the perceived loudness of the test tone at f1 due to the addition of the recalibration tone. Mapes-Riordan and Yost [J. Acoust. Soc. Am. 101, 3170(A) (1997)] showed that the temporal onset of loudness recalibration is relatively fast. The current set of experiments addressed the temporal decay properties of loudness recalibration. The first set of experiments examined the ‘‘local’’ temporal characteristics by measuring how the average amount of loudness recalibration varies with the duration of silent gap between the recalibration tone and the first comparison tone. A second set of experiments examined the ‘‘global’’ nature of the decay of loudness recalibration by inducing recalibration and then monitoring the decay using an adaptive tracking procedure. The results of these experiments will be discussed in terms of how assimilation processes influence loudness recalibration, what factors make the decay of loudness recalibration relatively slow, and the effect of attention on loudness recalibration. [Work supported by a Program Project Grant from NIDCD.]
The 3-D effect on underwater acoustic propagation in the offshore area of Taiwan’s coast
Authors: Chen Chi-Fang , Lin Jang-Jia , Wang Chung-Wu , Lee Ding
Published: July 2002

Lately 3-D effects on underwater acoustic propagation have frequently been reported. The major causes for the 3-D effects are the variations in azimuth of bottom topography or water column properties. The offshore regions of Taiwan’s coast are of the similar nature. There are submarine canyons in the offshore region of southwest Taiwan. The acoustic propagation is studied numerically using FOR3D. The 3-D effect is found to be more serious along the axis of the canyon’s axis than cross the canyon. The field test is also conducted in the region; the measurements are well matched with the numerical results calculated by FOR3D, which indicates the actual 3-D effect exists in the real ocean environment. [Work supported by National Science Council of Republic of China.]
Nonlinearities in the bioeffects of ultrasound
Authors: Carstensen Edwin L.
Published: July 2002

Biological effects of ultrasound involve nonlinear phenomena (1) in the propagation of sound itself, (2) in the generation of acoustic cavitation, and (3) in the biochemistry, physiology, and pathology of the biological system. Most nonthermal bioeffects of interest to users of diagnostic ultrasound require acoustic pressures great enough that the wave can become distorted by nonlinear propagation. Under limiting conditions this process can increase the absorption parameter of weakly absorbing media by orders of magnitude and make the absorption parameter of a material such as water as great as the linear absorption coefficient of liver tissue. At low amplitudes the response of the bubbles is dominated by the acoustic pressure. At a critical acoustic pressure, however, the inertia of the surrounding medium becomes controlling. At this threshold of acoustic pressure a 10% or 20% increase in acoustic pressure leads to an increase in the collapse pressure in the bubble by orders of magnitude. The rates of biochemical processes, including denaturation of biological macromolecules, are exponential functions of the temperature. Whether the physical process of heating by ultrasound is linear or nonlinear, this leads to a very strong nonlinear dependence of thermal tissue damage and teratological effects upon the levels of ultrasound.
One-dimensional distributed modal sensors and the active modal control for planar structures
Authors: Tanaka Nobuo , Kikushima Yoshihiro , Fergusson Neil J.
Published: July 2002

This paper discusses distributed parameter sensors designed to extract vibration modes of a structure, as well as its active modal control. Compared to conventional point sensors such as accelerometers or displacement sensors, the distributed parameter sensors are superior to point sensors provided that they are properly designed. First, this paper overviews a conventional modal filter method using point sensors, and enumerates the problems they possess. To overcome the drawbacks of the point sensor-based modal filtering, a novel modal filtering technique based upon distributed parameter PVDF film sensors is proposed. This paper begins by discussing a design methodology for modal filtering using two-dimensional distributed sensors. Then, taking into consideration the applicability of the sensors, a design procedure for modal filtering using one-dimensional sensors is presented, the number, location, and shaping functions for the one-dimensional modal sensors being clarified. Furthermore, the modal filtering using the one-dimensional sensors is found to be applicable for two-dimensional structures subject to any “classical” boundary condition. Experimental results verify the capability of the desired modal filtering for both isolated and degenerate structural modes. Finally, using the modal sensors, experiments on active modal control are conducted, showing a significant suppression of the targeted mode without causing instability of the control system.
Sound propagation over convex impedance surfaces
Authors: Li Kai Ming , Wang Qiang , Attenborough Keith
Published: July 2002

Theoretical calculations for the diffraction of sound by large spheres and cylinders with finite impedance surfaces are reported. The differences between existing two-dimensional and new three-dimensional results are made explicit and are shown to involve a simple correction factor in the case of a large sphere. The results for propagation over an infinitely long cylinder have a bearing on the widely used analogy between sound propagation over a curved surface and sound propagation in a refracting atmosphere above an impedance plane. Specifically, it is found that there is a rigorous analogy between sound propagation above a large circular cylinder and propagation in a medium where the sound speed varies exponentially with height. This differs from the bilinear profile that is often used when exploiting the analogy [see, for example, J. Acoust. Soc. Am. 83, 2047–2058 (1988)]. Predictions for both profiles are found to agree well with each other and with the published data in the shadow zone, but considerable discrepancies are found in the penumbra region.
Comparison of two semantic-differential test methods
Authors: Parizet Etienne
Published: July 2002

Two methods for conducting a multidimensional test were investigated. In the first and classical one, a sound (or a pair of sounds) is presented to the subject, who has to evaluate it (or compare the two sounds) for the various semantic parameters. In the second one, the test is repeated for each parameter (i.e., subjects must evaluate the whole set of sounds for the first parameter, then again for the second one, and so on). These two methods were compared on the basis of five diesel engine noises in small cars driving at idle. Sounds were compared in pairs for seven parameters (pleasant, loud, etc.). The characterization of sounds thus obtained was similar for the two methods. The second one proved to be more accurate (the accuracy is evaluated on the basis of repetition and triadic errors) and with a shorter duration than the first one, because listeners are concentrated on the selected sound parameter while hearing a new stimulus. Therefore, this method is recommended for conducting semantic differential tests.
Laser-generated nonlinear Rayleigh waves with shocks
Authors: Lomonosov A. , Mikhalevich V. G. , Hess P. , Knight E. Yu. , Hamilton M. F. , Zabolotskaya E. A.
Published: July 2002

Intense laser radiation was used to generate a Rayleigh wave pulse of finite amplitude in fused quartz. Measurements of the pulse at two locations along the propagation path reveal the formation of well-defined shocks in the horizontal (in-plane) velocity waveform. As the pulse propagates, the different propagation speeds of the head and tail shocks lead to a considerable increase in the duration of the pulse. Theoretical predictions based on nonlinear spectral evolution equations are in close agreement with the observed waveform distortion and shock formation.
Human auditory cortex electrophysiological correlates of the precedence effect: Binaural echo lateralization suppression
Authors: Liebenthal Einat , Pratt Hillel
Published: July 2002

Echoes lagging shortly after a sound and originating from a different location blend with the sound source perceptually. The location of the fused “source+echoes” is dominated by the source, suggesting suppression of echo localization. This effect is diminished monaurally, implying involvement of binaural processing. The neural substrates underlying the echo localization suppression are still unclear. The electrophysiological indications of primary auditory cortex involvement in binaural suppression of echo lateralization are presented. Position judgment and auditory-evoked potentials (AEPs) were recorded to single- and pairs of binaural and monaural clicks. The pairs simulated a source and its echo. The binaural source+echo position judgment was dominated by the source at small echo lags. With lag increase, it shifted toward the echo. The AEPs were studied for binaural processes specific to a “real” echo, as opposed to an identical single sound (a “virtual” echo). A reduction in binaural peak amplitude and area and an increase in binaural peak latency were detected specifically in the real echo-evoked middle-latency component Pa. The binaural echo Pa suppression depended upon echo lag, although less strongly than the psychoacoustic position judgment. Pa is associated with primary auditory cortex activity, thus suggesting primary cortical involvement in echo-lateralization suppression.
A comparison of intergestural patterns in deaf and hearing adult speakers: Implications from an acoustic analysis of disyllables
Authors: Okalidou Areti , Harris Katherine S.
Published: July 2002

Coarticulation studies in speech of deaf individuals have so far focused on intrasyllabic patterning of various consonant–vowel sequences. In this study, both inter- and intrasyllabic patterning were examined in disyllables /ə#CVC/ and the effects of phonetic context, speaking rate, and segment type were explored. Systematic observation of F2 and durational measurements in disyllables minimally contrasting in vocalic ([i], [u,] [ɑ]) and in consonant ([b], [d]) context, respectively, was made at selected locations in the disyllable, in order to relate inferences about articulatory adjustments with their temporal coordinates. Results indicated that intervocalic coarticulation across hearing and deaf speakers varied as a function of the phonetic composition of disyllables (b ̲b or d ̲d). The deaf speakers showed reduced intervocalic coarticulation for bilabial but not for alveolar disyllables compared to the hearing speakers. Furthermore, they showed less marked consonant influences on the schwa and stressed vowel of disyllables compared to the hearing controls. Rate effects were minimal and did not alter the coarticulatory patterns observed across hearing status. The above findings modify the conclusions drawn from previous studies and suggest that the speech of deaf and hearing speakers is guided by different gestural organization.
Virtual localization improved by scaling nonindividualized external-ear transfer functions in frequency
Authors: Middlebrooks John C.
Published: July 2002

This study examined virtual sound localization in three conditions that differed according to the directional transfer functions (DTFs) that were used to synthesize the virtual targets. The own-ear and other-ear conditions used DTFs measured from listeners’ own ears and those measured from other subjects, respectively. The scaled-ear condition employed other-ear DTFs that were scaled in frequency to minimize the mismatch between spectral features in the listener’s and the other subject’s DTFs. All measures of localization error typically were lowest in the own-ear condition. In other-ear conditions, all error measures tended to increase in proportion to the inter-subject differences in DTFs. When spectral features in an other-ear set of DTFs fell systematically lower in frequency than in a listener’s own DTFs, low frontal targets typically were reported as low in the rear, and high rear targets were reported as high in front. When spectral features in a set of DTFs fell systematically higher in frequency than in a listener’s own DTFs, elevation judgements showed an upward bias. In the scaled-ear condition, all measures of performance tended to improve relative to the other-ear condition. In the majority of cases, frequency scaling more than halved the penalty for use of another subject’s DTFs.
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b(r) version of CHIEF (Combined Helmholtz Integral Equation Formulation) for solving acoustic radiation and scattering problems
Authors: Forsythe Steve
Published: July 2002

The CHIEF program was developed during 1965–1988 at the Naval Ocean Systems Center. It was written in FORTRAN. The program uses the surface integral formulation of the Helmholtz equation to solve for acoustic pressure and velocity over a surface subject to surface geometry, boundary conditions, and incident field pressure on the surface. CHIEF uses a file interface to specify geometry, boundary conditions, etc., and writes its solutions for surface pressures to an output file. Thus, other programs are required for surface visualization and interpretation of results. Further, much of the original CHIEF FORTRAN code is devoted to bookkeeping imposed by machine limitations. As part of a larger modeling effort, CHIEF was ported to matlab. This makes the CHIEF methodology available as part of the matlab workbench approach to programming. Bookkeeping code that is no longer needed is discarded. Visualization tools are included as part of the new CHIEF environment. matlab functions are used where appropriate, combined with C++ code for speed when performing operations that are not vectorizable by matlab. The object-oriented features of matlab CHIEF are discussed as they apply to problem definition, visualization, and clarity and conciseness of programming. [Work supported by ONR 321 as Acoustic Measurement Methodology.]
Vocal tract size and the intelligibility of competing voices
Authors: Assmann Peter F.
Published: July 2002

When two people speak at the same time, it is easier to understand what either is saying if the voices differ in fundamental frequency (F0). Talkers differ in vocal tract size as well as F0, and their formant frequencies occupy different ranges, providing a further basis for voice segregation. To investigate the effects of vocal tract size, a set of declarative English sentences was produced by an adult male and processed using a speech vocoder. Sentences were presented in pairs, with the spectrum envelope shifted up or down by a fixed percentage in one of the sentences. A +20% shift (sufficient to shift the formants of an adult male into the female range) led to a 6% increase in word recognition accuracy. A −20% shift led to a 9% drop in accuracy, consistent with listeners’ informal reports that the ‘‘larger’’ voice sounded muffled. Benefits of upwards shifts and adverse effects of downward shifts were restricted to the ‘‘shifted’’ member of the pair. Upward spectral shifts were accompanied by increased spectral tilt, while downward spectral shifts led to reduced spectral tilt. Hence the observed effects may be due to spectral masking, rather than sensitivity to vocal tract size per se.
Optimal array element localization
Authors: Dosso Stan E. , Sotirin Barbara J.
Published: July 2002

Advanced array processing methods require accurate knowledge of the location of individual elements in a sensor array. Array element localization (AEL) methods are typically based on inverting acoustic travel-time measurements from a series of controlled sources at well-known positions to the sensors to be localized. An important issue in AEL is designing the configuration of source positions: a well-designed configuration can produce substantially better sensor localization than a poor configuration. In this paper, the effects of the source configuration and of errors in the data, source positions, and ocean sound speed are quantified using a sensor-position error measure based on the a posteriori uncertainty of a general formulation of the AEL inverse problem. Optimal AEL source configurations are determined by minimizing this error measure with respect to the source positions using an efficient hybrid optimization algorithm. This approach is highly flexible, and can be applied to any sensor configuration and combination of errors; it is also straightforward to apply constraints to the source positions, or to include the effects of data errors that vary with range. The ability to determine optimal source configurations as a function of the number of sources and of the errors in the data, source positions, and sound speed allows the effects of each of these factors to be examined quantitatively in a consistent manner. A modeling study considering these factors can guide in the design of AEL systems to meet specific objectives for sensor localization.
The auditory continuity phenomenon: Role of temporal sequence structure
Authors: Drake Carolyn , McAdams Stephen
Published: July 2002

The auditory continuity phenomenon occurs when listening to a series of alternating high- and low-level tones: instead of perceiving this intermittence, listeners often report hearing a continuous tone upon which is superimposed a series of intermittent tones. The temporal limits to the perception of this phenomenon are investigated, as well as effects of task instructions on it. A loudness-matching paradigm developed previously [McAdams et al., J. Acoust. Soc. Am. 130, 1580–1591 (1998)] provided both an objective indication of this phenomenon and an indication of its strength. In the studies reported here, the phenomenon was observed reliably when the low-level tones were at least half the duration of the high-level tones: the greater the duration ratio between low-level and high-level tones, the stronger the phenomenon. Duty-cycle duration did not affect the strength of this phenomenon. It proved to be particularly robust as its strength was unaffected by task instructions, level of expertise, and repetition. A model is proposed in which adjusted levels depend on the relative levels of the high- and low-level tones weighted by relative duration and attentional focusing.
The Rayleigh-like collapse of a conical bubble
Authors: Leighton T. G. , Cox B. T. , Phelps A. D.
Published: July 2002

Key to the dynamics of the type of bubble collapse which is associated with such phenomena as sonoluminescence and the emission of strong rebound pressures into the liquid is the role of the liquid inertia. Following the initial formulation of the collapse of an empty spherical cavity, such collapses have been termed “Rayleigh-like.” Today this type of cavitation is termed “inertial,” reflecting the dominant role of the liquid inertia in the early stages of the collapse. While the inertia in models of spherical bubble collapses depends primarily on the liquid, experimental control of the liquid inertia has not readily been achievable without changing the liquid density and, consequently, changing other liquid properties. In this paper, novel experimental apparatus is described whereby the inertia at the early stages of the collapse of a conical bubble can easily be controlled. The collapse is capable of producing luminescence. The similarity between the collapses of spherical and conical bubbles is investigated analytically, and compared with experimental measurements of the gas pressures generated by the collapse, the bubble wall speeds, and the collapse times.
Acoustic scattering from two circular apertures in a thick hard plane
Authors: Seo Jin S. , Eom Hyo J. , Lee Haeng S.
Published: July 2002

A problem of acoustic wave scattering from two circular apertures in a thick hard plane is solved. The Hankel transform and mode matching is used to represent the scattered field in rapidly convergent series. The reflection coefficient, transmission coefficient, and far-zone field are rigorously derived and presented in numerically efficient forms. Numerical computations are performed to illustrate scattering behaviors in terms of aperture geometry.
Weakly localized waves on the corrugated surface of a medium of arbitrary anisotropy
Authors: Darinskii A. N.
Published: July 2002

The existence of weakly localized surface and pseudosurface waves on the corrugated surface of a medium of arbitrary symmetry is studied. The localized solution originates from an exceptional bulk wave associated with a transonic state of positive or negative curvature. It is shown that the period of corrugation or the frequency of the wave can universally be chosen such that the solution will exist. The range of permissible periods (frequencies) is different for positive and negative curvature transonic states, it being wider near transonic states of positive curvature. The imaginary component of the pseudosurface wave velocity is found to vary as the height of grooves to period of corrugation ratio raised in fourth or sixth power, depending on the transonic state with which the exceptional wave is associated. A simple analytical expression is derived allowing estimations to be made of the penetration depth and the velocity of the localized wave.