bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of the inverse estimator for reconstructed temperature and current fields
Authors: Nakano Iwao
Published: October 2005

The inverse scheme is not optimized under the formalized condition in solving an inverse problem of ocean acoustic tomography. But if how the travel time bias can affect the reconstructed profiles is examined, it is useful to determine the optimal bias for each inversion. There are two methods to determine this bias. One is to minimize the variance of the sound-speed anomaly as a function of travel time bias. The other is to use the formula derived by the minimization of the variance of the difference of true and estimated sound-speed anomalies. Even though both results must agree with each other in principle, they are not always the same. In examining the discrepancy, the assumption can be made that the inverse scheme is optimal which minimizes the difference of both biases. Moreover, the travel time bias makes it possible to treat with barotropic mode of current and temperature separated from baroclinic modes.
Effects of the California ATOC experiment on marine mammals
Authors: Costa Daniel P. , Crocker Daniel E. , Croll Don , Goley Dawn , Houser Dorian , LeBoeuf Burney J. , Waples Danielle , Webb Paul , Calamabokidus John
Published: October 2005

The effect of the California ATOC experiment on marine mammals has been studied using aerial surveys to observe changes in marine mammal abundance. Dramatic changes in behavior have not been observed while the source was operating. The following species have been sighted in the area humpback, sperm, gray, fin, pilot, and killer whales, Baird’s and Cuvier’s beaked whales, elephant seals, California sea lions, northern fur seals, Risso’s, Pacific white-sided and northern right whale dolphins, and Dall’s porpoise. Satellite and archival tags were used to record the behavior of elephant seals as they passed by the ATOC sound source. Tracks of male elephant seals passing by the Pioneer Seamount were closer on their return migration when the source was on than on their outbound path when the source was off. Acoustic data loggers were deployed on juvenile elephant seals that were released by boat near the ATOC sound source. These units collected data on diving and swimming behavior concurrently with recordings of the ATOC source sound pressure level at the animal. [Work supported by the Strategic Environmental Research and Development Program through ARPA and the Office of Naval Research.] 43.30.Sf
The precision of travel time in ATOC experiments
Authors: Dzieciuch Matthew , Colosi John , Cornuelle Bruce , Munk Walter , Worcester Peter , Flatté Stanley M. , Dushaw Brian D. , Howe Bruce M. , Mercer James A. , Spindel Robert C.
Published: October 2005

Acoustic-ray travel-time measurements at 75 Hz are being used in the ATOC tomography experiment to infer important oceanographic variables such as heat content, currents, etc. The accuracy with which these measurements can be made is limited by the small-scale structure of the ocean (such as internal waves). Examined in detail, rayfronts show variations in time, depth (for a vertical array) and in pulse shape. At ranges of up to 5 Mm, coherence times of greater than 10 min, vertical coherence lengths of greater than 500 m, and rms pulse variability (spread and wander) of less than 50 ms were the norm. Comparison of these observations with predictions based on internal-wave effects will be described. Although the numbers above are preliminary estimates, the basic result is clear, basin scale measurements can be used to effectively monitor climate. Travel times can be measured by modal filtering as well as by ray beamforming. Methods to interpret these measurements will also be discussed. [Work supported by the Strategic Environmental Research and Development Program through ARPA.]
North Pacific basin heat content variability determined from long-range acoustic transmissions
Authors: Howe Bruce M. , Dushaw Brian D. , Mercer James A. , Spindel Robert C. , Worcester Peter F. , Cornuelle Bruce D. , Colosi John A. , Dzieciuch Matthew A. , Munk Walter H. , Metzger Kurt
Published: October 2005

ATOC signals transmitted from the Pioneer Seamount acoustic source have been received on hydrophone arrays located throughout the North Pacific Basin since the beginning of 1996. Propagation times can be used to infer average temperature (or heat content) variability because the speed of sound changes with temperature. The time series of resolved-ray travel times show both an annual cycle with amplitudes up to 0.5 s, and other higher frequency fluctuations of comparable magnitude caused by natural oceanic variability. The range-averaged temperature is derived from the low-pass filtered (<1 cpd) resolved-ray travel times by constructing a model for the structure and statistics of oceanic variability, fitting the model to the data using weighted least-squares techniques, and then calculating the range- and depth-averaged quantity including its uncertainty. Because many of the resolved rays reflect off the sea surface, the mixed layer in particular, and the upper ocean in general, must be correctly modeled. The variability of acoustically determined heat content is compared to that determined from the Levitus94 atlas, historical expendable bathythermograph (XBT) data; other concurrent data types are not yet available for direct comparison. [Work supported by the Strategic Environmental Research and Development Program through ARPA.]
Smart actuator for acoustic surface control
Authors: Corsaro Robert D. , Klunder Joseph D. , Herdic Peter , Kraus Larry
Published: October 2005

Acoustic radiation or reflection from a surface is a function of the surface impedance, which can be controlled using smart sensor–actuator systems. In this study a smart surface coating is developed using a 1-3 composite actuator with embedded accelerometers. This active coating can be electronically varied to present a wide range of impedance conditions. A feature of this system is its low fabrication cost: It is formed by an injection molding process developed by Material Systems, Inc. (MSI) which allows the accelerometer and actuator to be co-formed in one fabrication step. This paper describes the design, performance, and control issues related to smart surfaces formed using this process. Applications in underwater acoustics and structural vibration control are considered.
High-power, high-frequency, broad constant beamwidth 1-3 composite transducer
Authors: Allen Charles W. , Hughes W. Jack
Published: October 2005

A difficult transducer design is to produce broad beamwidths with high power at high frequencies. Transducers formed on a cylindrical arc can produce broad beamwidths with greater power than conventional planar transducers with the same beamwidths because of their larger area. These transducers also have the added benefit of directivity patterns, with constant beamwidth as a function of frequency, instead of the typical decreasing beamwidth as with conventional planar transducers. The utilization of 1-3 PZT composite piezoelectric material enhances the performance and simplifies construction of constant beamwidth transducers due to its ability to be easily formed into a cylindrical arc using a single piece of material several wavelengths in dimension. Test results show that a 1-3 composite constant beamwidth transducer provides almost a 10 dB higher source level than a comparable 1-3 composite planar transducer. The constant beamwidth transducer also produces a 70° constant beamwidth directivity pattern from 75 to 300 kHz. This device is being used as a broad bandwidth standard transducer because of its stable pattern characteristics.
Arrays fabricated for Naval Research Laboratory using 1-3 composite and PVDF sensor materials
Authors: Hughes W. Jack
Published: October 2005

There has been considerable effort for a number of years at ARL Penn State in using 1-3 PZT composite and PVDF material in the design and fabrication of transducers and arrays. The 1-3 PZT-5H composite material was used to design and fabricate two large-area, shaped-aperture transmit arrays (50–100 kHz and 100–200 kHz) for ocean acoustics measurements performed at the Naval Research Laboratory at Stennis Space Center. These arrays produced 1- to 2-deg vertical beamwidths and horizontal beamwidths of 50 to 100 deg at source levels greater than 200 dB. An acoustic dispersion lens was designed for the higher frequency array so that high-power source levels and broad horizontal beamwidths could be achieved. The material being used is the injection molding composite produced by Material Systems, Inc., consisting of 30% PZT-5H by volume, Shore D-80 hardness voided matrix material. A receive array having the same beamwidth characteristics was fabricated from voided PVDF which was manufactured by Raytheon (now produced by Air Mar Corp.). Nested shaped sensors were etched onto the PVDF using printed circuit board techniques. Shaped sensors have demonstrated low sidelobe patterns in the axial plane. Design and test data will be presented.
Development and experimental evaluation of a bond graph model of the thickness vibrator
Authors: Moon Wonkyu , Busch-Vishniac Ilene J.
Published: October 2005

Thermal behavior is successfully included in a model for the piezoelectric thickness vibrator. The process of building this complete model consists of four steps. The first step is thermodynamic consideration of material properties. Second, the governing partial differential equations, including thermodynamics, are derived for the general case of a piezoelectric material and applied to the specific case of a thickness vibrator. The third and fourth steps are a bond graph analysis of the thickness vibrator, under conditions of heat conduction only, and for the full electro–mechano–thermal interactions. Among the proposed two simple material property models, the isentropically linear and isothermally linear models, the former is selected for the bond graph model as it makes the analysis easier and can be shown to produce very little difference from the isothermally linear assumption. In order to evaluate the usefulness of the developed modeling method for design of transducers, the calculation results for a simple case are compared with the results from experiments. In general, the predictions and the experimental data agree well.
Acoustical evaluation of a 1-3 piezocomposite array for high-frequency sonar application
Authors: Ting Robert Y.
Published: October 2005

New piezoelectric 1-3 composite materials containing ceramic rods embedded in a polymeric matrix have been shown to exhibit excellent piezoelectric properties for sonar transducer applications. A 4×10 hydrophone array was recently fabricated by using injection-molded 1-3 piezocomposites of PZT-4 ceramic and a polyurethane resin. The array panel was evaluated in the Anechoic Tank Facility at USRD in Orlando, FL. Free-field voltage sensitivity, directivity pattern and interelement phase relationship were determined as a function of temperature, pressure, and frequency (up to 200 kHz). Element-to-element uniformity within the array was observed. Pressure and temperature stabilities of the panel were also demonstrated up to 7 MPa at 3 °C. The ability of this 1-3 composite array to detect low-sound pressure levels was also shown in comparison with similar arrays of other materials such as lead titanate ceramic and piezorubber composite. These test results indicate that 1-3 piezocomposite is a promising candidate for application in high-frequency sonar transdu- cers. [Work supported by ONR.]
Two-dimensional modeling and characterization of PMN electrostrictive materials using the finite-element code ATILA
Authors: Debus J. C. , Dubus B. , Dubois J. , McCollum M. , Black S.
Published: October 2005

New electrostrictive lead magnesium niobate ceramics (PMN) are promising materials for applications in the field of actuators, transducers, and motors. These materials have strains roughly an order of magnitude larger than those of the lead zirconate–titanate (PZT) ceramics. However, the use of these electrostrictive materials for practical applications presents some difficulties: highly nonlinear properties, temperature dependence of dielectric permittivity near the dielectric maximum, dc bias field needed. To improve the use of these electrostrictive materials, a better knowledge of the physical tensors of PMN and the development of a numerical tool are necessary. In this study, the development of a two-dimensional electrostrictive element in the ATILA code for nonlinear static analysis and time-domain analysis is presented. Two different models are tested including or not the effect of polarization saturation. The validity of both models is demonstrated by comparing computed strain and charge density with analytical solutions and measured results for a PMN bar at various electric dc fields and mechanical prestresses. Measurements are realized to obtain the complete physical tensor of PMN. Finally, the model is applied to a Janus transducer to describe the application of prestress and the electrical dc polarization.
Experimental modal analysis comparison of the vibration damping properties of composite cylinders measured in-air and underwater
Authors: Ratcliffe Colin P. , Crane Roger M. , Santiago Armando L.
Published: October 2005

Self-noise is problematic in many underwater applications, since it interferes with the performance of onboard sensors. To reduce self-noise, experiments investigated using composite materials for cylinders subjected to hydrostatic pressure loading. This paper presents the test procedure and results of modal analysis testing conducted in-air and underwater on some composite cylinders. The in-air tests used impact force excitation, whereas the underwater tests used sound excitation. The results include resonant frequencies, damping factors, and mode shapes at resonance. In order to ensure a valid comparison, the natural frequencies and damping factors are compared on a mode-by-mode basis. Despite the increased complexity of the underwater experiments, it is shown that the in-air and underwater levels of damping observed at relatively low frequencies are comparable. Further, an appropriate choice of composite materials can increase damping by at least an order of magnitude over conventional metals. The damping can additionally be increased by using a double-hollow core or triple-shell configuration, with reinforced polyurethane ribs. The paper discusses this new reinforced polyurethane as a structural component of the cylinder, and proposes various mechanisms of damping that this material form provides.
Acoustic plane-wave reception by a single-axis velocity sensor aligned normally on an air-voided elastomer backed by an elastic plate
Authors: Ko Sung H. , Schloemer Howard H.
Published: October 2005

A theoretical model was developed to evaluate the acoustic plane-wave reception by a velocity sensor placed near an air-voided elastomer baffle layer backed by an elastic plate. The air-voided elastomeric baffle layer is designed to reduce the noise generated by the motion of the elastic plate and enhance the acoustic wave received by a velocity sensor with its axis perpendicular to the layer. The plate is perfectly bonded to the elastomeric baffle. The outer surfaces of the elastic plate and the elastomer baffle are in contact with air and water, respectively. The analysis for modeling is based on the theory of elasticity and pertinent boundary conditions. Computations were made using different properties for the elastomer. These computations show that by proper material and thickness selection the acoustic reception may be varied significantly as a function of frequency. [Work supported by the Office of Naval Research, Code 321SS.]
Visualization of the power reduction of piezorubber underwater array by near-field acoustic intensity measurement
Authors: Mikami Daiji , Yokoyama Tomoki , Hasegawa Akio , Kikuchi Toshiaki
Published: October 2005

The mutual radiation impedance, which acts among transducer elements vibrating in the medium, is one of the most important factors for considering the interaction of recent high-power and low-frequency sonar arrays and active acoustic control. The mutual radiation impedance is numerically obtained from an equation of directional functions. When the amplitude of one of two transducer elements is changed, the total and individual power output become quadratic curves with minimum peaks as a function of amplitude. This minimum peak of the total power output curve means that there is the most effective vibrating velocity amplitude for the additional or the secondary source to minimize the total power output from the original or the primary source. The measurement of the acoustic intensity from the underwater array made of piezorubber sheet visualizes the phenomena of the total power output reduction. Near-field 3-D maps of the active intensity l and the reactive intensity Q show some interesting patterns of energy flow in the vicinity of transducers especially in low-frequency regions.
Noise of a high-speed vehicle using resilient wheels and brake discs
Authors: Satoh Kiyoshi , Sagawa Akio , Matsui Yuji , Satoh Toshikazu
Published: October 2005

Reduction of rolling noise as well as aerodynamic noise still calls for serious attention to controlling Shinkansen noise, even if the speed of the train comes close to 300 Km/h. This paper presents estimation results of wheel/rail noise based on the field tests, in which two comparisons of noises under different wheel conditions were carried out. The first comparison concerns the noise of solid wheels or of resilient wheels, which were adopted, tentatively aiming to lessen the rail vibration. The second concerns the noise of wheels running normally with brake discs or of wheels tentatively without the discs. The effects of using resilient wheels and brake discs on wheel/rail noise are estimated as follows. (1) In-car noise and 25-m point noise can be lowered by 1 to 2 dB when uisng resilient wheels as a result of attenuation by transmission or diffraction at higher frequencies. (2) The structure noise decreasing effect of resilient wheels proves to be at least 3 dB. (3) It is ascertained that the braking system in Shinkansen using brake discs fixed to wheel webs gives an advantage of lowering the sound possibly caused by the wheel vibration.
Structure-borne noise in buildings from subway trains
Authors: Wilson George P.
Published: October 2005

Projection of the expected noise in multifloor or high-rise buildings due to ground-borne vibration from subway trains requires estimating the propagation of the noise up through the buildings via structure-borne transmission. Recent measurements have shown that the actual results can be substantially different than projected based on studies previously reported. Measured data indicate nominal attenuations in the range of 0 dB per floor to 2.5 dB per floor can be expected, depending on building construction configuration. Data for the building types and attenuations measured are presented.
Application of FTA criteria to assess transit noise and vibration impacts in residential areas
Authors: Balachandran Chetlur G. , Brown James R.
Published: October 2005

This paper presents the results of noise and vibration analyses that were performed at six residential sites adjacent to two rail tracks in an active suburban rail corridor to assess the potential impacts of proposed widening of the corridor in the year 2010 to accommodate a third track. The proposed third track would bring the trains closer to residences and would also increase the total number of train movements during a 24-h period. The project noise and vibration impacts were assessed in conformance with recently published FTA (Federal Transit Administration) manual ‘‘Transit Noise and Vibration Impact Assessment’’ (April 1995). Since the sites are exposed to both roadway noise and train noise, monitored hourly Leq noise levels were used to estimate the existing and the future Ldn noise levels. The FTA procedure replaces the maximum single passby noise standards used by APTA (American Public Transit Association) for over 20 years. Following the procedures outlined in the FTA manual, noise impacts were identified at three of the six residential sites, and noise walls at the three affected sites were recommended as mitigation. Also, mitigation options were recommended at two residences where potential vibration impacts were identified.
Scale-model investigation of highway noise barriers: Walls, earth berms, and earth berm/wall combinations
Authors: Busch Todd A. , Hodgson Murray R.
Published: October 2005

Scale-model roadside barriers were studied, using an air-jet to recreate a line source of traffic. Scale-model materials were selected by measuring their excess attenuation, at scale factors of 1:20, 25, 31.5, 40, and 50. For each material, the residuals between a measurement and a theoretical best-fit curves were calculated for each cell of a 2-D array whose axes were scale factor versus effective flow resistivity. An optimal scale factor of 1:31.5 was selected, in conjunction with the selection of three model materials to simulate earth berms and soft ground (150–300 cgs rayl), and vertical walls or roadways (20 000 cgs rayl). Roadways were simulated by varnished particle board, walls by dense polystyrene, and both earth berms and soft ground were simulated using extruded polystyrene. The insertion losses, with and without an A-weighted traffic-noise spectrum, were determined for 38 different noise-barrier configurations. Walls outperformed earth berms by 2 dBA; for earth berms, shallower slopes degraded insertion losses, but when a wall was present the opposite trend was observed. One of the most relevant references is [Hutchins et al., J. Acoust. Soc. Am. 75, 1817–1826 (1984)]. [Work supported by the B. C. Ministry of Transportation and Highways.]
Numerical study of shock and streaming in a nonlinear focused sound field
Authors: Yano Takeru
Published: October 2005

Propagation of nonlinear acoustic waves radiated from a spherically concave source into an ideal gas is numerically studied in the case where the dissipation effect is negligible everywhere except for the shock front. In order to obtain the precise wave profile including shock waves, a high-resolution upwind finite difference scheme is employed to solve the Euler equations of gasdynamics. The linear wave equation and the Zabolotskaya–Khokhlov equation are also solved by the high-resolution upwind scheme, and the results are compared with those obtained from the Euler equations. It is shown that moderately strong shocks cause strong streaming in the focal region. The maximum streaming velocity amounts to the particle velocity of the gas at the sound source.
High sound intensity by a two-tube structure
Authors: Liu Ke , Maa Dah-You
Published: October 2005

Nonlinear standing waves have been studied in a structure consisting of two lengths of tubing with different diameters. Preliminary theory of this structure is proposed. A 100-W loudspeaker driver is used as a sound source to excite the larger tube of 45-mm diameter through a 10-mm side hole near one end which is closed. The properties of the output at the end of the smaller tube as well as their relation with the input were investigated, and a resonance diagram of the two-tube structure is completed. At the end of smaller tube of 13-mm diameter, a sound-pressure level (SPL) of 176.2 dB has been obtained with a low distortion. Increasing the diameter of the larger tube, it is possible to drive the structure directly with a modern high power loudspeaker to produce high sound intensity in a more extended space. Experiments are in progress. [Work supported by the National Natural Science Foundation of China.]
Change of a period and tone-burst sinusoidal sounds to a stable soliton in a thin fiber of fused silica, under comparison with hyperbolic solitons
Authors: Nakamura Akira
Published: October 2005

Soliton formation processes for various waveforms given initially at an origin by using a valid computer algorithm will be discussed. Results obtained are as follows. The propagation behavior of a hyperbolic soliton governed by aKdV equation is described by three parameters which are pulse height, pulse width, and soliton velocity. A proportional relationship is found among these parameters. If a definite proportional constant is found in any propagation distance, it may be recognized that it is stable. In a dissipative medium, a different proportional constant from the one in a nondissipative medium is found. A negative sinusoidal pulse is changed to a hyperbolic one with propagation, while a positive pulse does not show any soliton. A period of sinusoidal waveform gives a soliton changing from a negative pressure part being in the waveform. The tone burst of a sinusoid with some wavelets also makes successively some solitons from the negative pressure part in the leading period to the one in the following period.
An analytical radial solution to O(ε4) of the Van der Pol–Rayleigh limit cycle oscillator
Authors: Raphael David T.
Published: October 2005

An analytical closed-form solution to O(ε4) of the Van der Pol–Rayleigh limit cycle oscillator is derived assuming a constant angular frequency as given by the Davis–Alfriend solution, with ε≤1. Using phase plane polar coordinates, the Van der Pol equation is transformed into a time-dependent radial equation. A variation-of-parameters approach is then employed to derive an exact infinite series expression involving modified Bessel functions and sinusoidal functions. The series is then simplified using a combination of a Sommerfeld–Watson technique in conjunction with a series reversal via an Euler transformation. The solution for the limit cycle radius can be reduced to a relatively simple mathematical form. The computed limit cycle paths with this radial solution correspond very closely to the true solution paths for ε≤1 and are demonstrated for comparison. Extension of this technique to the problem of large ε is discussed.
A comparative review of binaural synthesis for free-field simulation
Authors: Hammersho/i Dorte , Sandvad Jesper
Published: October 2005

The binaural synthesis technique is widely known and utilized for simulation of complex auditory scenarios, as, for instance, seen in the many concepts of ‘‘virtual reality.’’ The simulated environments offer attractive test scenarios for human factors research, assuming that the subject’s behavior in the simulated environment is the same as it would have been in the corresponding real-life situation. A number of investigations have been carried out worldwide to verify the synthesis technique, and only a few seem to have obtained satisfactory results. In the present paper the results from contemporary studies (including the authors own) are presented and discussed.
Evaluation of artificial head recording systems
Authors: Mo/ller Henrik , Jensen Clemen Boje , Hammersho/i Dorte , So/rensen Michael Friis
Published: October 2005

Artificial head (or dummy head) recording and playback systems are increasingly used. The main advantage of these systems is their ability to reproduce three-dimensional spatial aspects of sound. However, the exact reproduction of direction has been questioned from time to time. The study presents an objective and subjective evaluation of eight artificial heads. In the objective test, the head-related transfer functions of the heads were compared to those of humans. Significant deviations were seen for all heads, and none of them can be characterized as a mean, median, or typical head. In the subjective test a panel of listeners indicated direction and distance to sound sources recorded by the head and reproduced by means of carefully equalized headphones. The reproduction of direction was in general poor, especially in the median plane.
Auditory localization of a nearby point source
Authors: Brungart Douglas S. , Rabinowitz William M. , Durlach Nathaniel I.
Published: October 2005

Although human auditory localization has been studied extensively in the past century, little is known about the localization of nearby sound sources. The head-related transfer function (HRTF) contains all relevant localization information and has been thoroughly examined for relatively distant sources, but may exhibit unique properties in the ‘‘near-field’’ region within 1 m of the center of the head. A rigid-sphere computational model of the head has been used to estimate near-field HRTFs, and a KEMAR manikin and a specialized acoustic ‘‘point’’ source have been used to measure HRTFs for sources as close as 0.25 m. For a fixed source direction, the interaural time delay is roughly independent of distance, but the interaural amplitude difference increases dramatically as the source approaches within 1 m of the head. When the source is near one ear, the interaural amplitude difference exceeds 20 dB across the audio spectrum. The differences between near-field and more distal HRTFs will be discussed, including comments on how near-field effects may facilitate three-dimensional localization judgments. In addition, preliminary results of a psychoacoustic experiment designed to measure human localization performance for sources within ‘‘arm’s reach’’ of the listener may be presented. [Work supported by AFOSR and NIDCD].
Anomalous lateralization in the precedence effect with novel two-echo stimuli
Authors: Tollin Daniel J. , Henning G. Bruce
Published: October 2005

The precedence effect refers to the well-known observation that the perceived location of two binaurally presented transient stimuli that are separated by a brief delay depends primarily on the properties of the first arriving sound. In this study, the precedence effect was investigated using 20-μs pulses presented over headphones. Three pulses were presented to each ear simulating a sound coming from directly in front followed by an echo from the side and then from the rear: The first and last binaural pair of pulses were diotic while the middle binaural pair was dichotic with either interaural differences in time or level. A 2AFC lateralization paradigm was used. Highly anomalous lateralization (i.e., lateralization performance near 0%) was observed for many interpulse delays when the total stimulus duration was 2 ms or less. The anomalous results are explained by considering the spectral characteristics of the stimuli.
Discrimination of noise modulators
Authors: Sheft Stanley , Yost William A.
Published: October 2005

Noise discrimination ability was measured with a cued 2IFC procedure in which a wideband noise carrier was modulated by bandlimited noise. Modulator bandwidth was constant for the three stimulus presentations on each trial with the signal-interval modulator a repetition of the cue modulator. The modulator bandwidth ranged from 10 to 5000 Hz. The carrier was either a random or frozen sample of wideband noise across the three presentations per trial. In these conditions, discrimination among noise samples is based solely on envelope and not fine-structure characteristics. Performance was better with the frozen rather than random carrier samples with discrimination ability inversely related to modulator bandwidth. Data trends were modeled with an envelope detector providing the input to a sequential equalization-cancellation mechanism. In a second set of conditions, rippled noise was used as the modulator for the cue and signal intervals. Ripple delay ranged from 1 to 64 ms with the number of iterations ranging from 1 to 16. The ability to discriminate between rippled and Gaussian modulators of equal bandwidth increased with the number of iterations and was also inversely related to delay, suggesting a type of envelope processing similar to that involved in pitch perception. [Work supported by NIH.]
Effects of deviations from temporal expectations on tempo discrimination
Authors: McAuley J. Devin , Kidd Gary R.
Published: October 2005

Effects of deviations from temporal expectations on tempo discrimination were examined using eight-tone isochronous sequences with a fixed inter-onset-interval (IOI) of 400 ms. On each trial, the eight-tone standard sequence was followed by a two-tone comparison sequence with an IOI that was shorter, longer, or the same as that of the standard. Temporal deviations were introduced by advancing or delaying the onset of the comparison sequence relative to the ‘‘expected’’ onset time, defined as an extension of the periodicity of the standard (800 ms after the onset of the last tone) and reinforced on every trial in the first trial block. Discrimination thresholds and points of subjective equality were determined for early, late, and expected onsets under mixed and blocked presentation of the onset conditions. Under mixed presentation, early onsets produced more ‘‘shorter’’ judgments and late onsets produced more ‘‘longer’’ judgments. Timing also affected sensitivity, with lower thresholds for tempo increases in the early-onset conditions and lower thresholds for tempo decreases in the late-onset conditions. No such systematic shifts in bias and threshold were observed with the reduced temporal uncertainty of blocked presentation. Implications for interval- and entrainment-based models of time perception are discussed. [Work supported by a UQ postdoctoral fellowship and NIDCD.]
Differences in speaker’s articulatory space: Their contribution to vowel gesture and acoustic pattern
Authors: Honda Kiyoshi , Wu Chao-Min
Published: October 2005

The view that individual speaker characteristics reflect morphological and functional differences in the speech apparatus has been accepted as self-evident despite the lack of convincing empirical data. A recent study on the issue of individual differences based on x-ray microbeam data from ten American English and ten Japanese speakers (five males and five females in each group) has pointed to a significance of morphology in accounting for speaker characteristics of vowel gesture. The midsagittal form of a speaker’s orofacial structure was parametrized by several landmarks on x-ray scan images. A few points and lines were chosen to form a quadrilateral framework so that they define a geometrical ‘‘articulatory space’’ where articulation of the tongue–jaw complex takes place. Pellet data for vowels were mapped onto speaker’s articulatory space to observe the effect of morphological difference on vowel articulation. Preliminary results have shown the extent of morphological variation of the speech apparatus and adaptability of vowel gesture to different forms of the space. The aspect ratio of the articulatory space was judged as the primary causal factor of articulatory variation. Acoustic manifestation and perceptual contribution of the variation will be discussed from a viewpoint of auditory-articulatory linkage.
Variation in speech movement kinematics and temporal patterns of coarticulation with changes in clarity and rate
Authors: Perkell Joseph S. , Matthies Melanie L. , Perrier Pascal
Published: October 2005

It is hypothesized that segmental speech movements are programmed to achieve perceptual objectives, by realizing articulatory and acoustic goals. As demands for clarity and rate change, movement kinematics and coarticulation will be adjusted in a trade-off between clarity and economy of effort. In a preliminary test of these ideas, articulatory and acoustic signals have been recorded from two speakers under different conditions of clarity and rate. Effort-related measures are calculated from kinematic data on the tongue body, tongue blade and lips; degrees of labial and lingual coarticulation are measured from timing data, and correlates of clarity are calculated from acoustic data. Initial results indicate a complicated picture, with differences among articulators and between the two subjects. In general, one mediating factor seems to be the influence of basic principles of motor control, reflected in such relationships as duration versus movement distance and velocity versus distance. The results will be discussed in relation to the idea that speakers use an internal representation of relations between articulatory and perceptual domains to help manage the trade-off between listener-oriented perceptual requirements and a speaker-oriented objective to conserve effort. [Work supported by NIDCD.]
Representational specificity of lexical form: Implications for models of spoken word recognition
Authors: Luce Paul A. , Vitevitch Michael S. , Gaygen Daniel E. , Lyons Emily A.
Published: October 2005

Much recent work on spoken-word recognition has suggested that the representation of phonological form in memory is quite specific and veridical, coding such lexically nondistinctive information as talker voice and allophonic variation. The implications of this research for current models of spoken word recognition will be discussed. In particular, exemplar-based approaches to modeling spoken word recognition and the need for multiple levels of representation of sound patterns in memory, ranging from specific, instance-based representations to more general, abstract phonological forms will also be discussed.
A perceptual experiment on voice individuality by altering pitch and formant frequencies
Authors: Kuwabara Hisao
Published: October 2005

No single acoustic parameter is believed to characterize solely voice individuality. A perceptual experiment has been performed concerning the voice individuality of human speech sounds making use of an analysis–synthesis method which is capable of independent manipulation of formant frequencies, bandwidths, and pitch frequencies. Pitch and formant frequencies are the two most important acoustic parameters for speech science and technology. This experiment has been performed to examine which parameter carries more information or is more robust, in terms of voice individuality, against acoustic distortion. Experimental results reveal that the perception of voice individuality is far more sensitive to the formant frequencies than the pitch frequency. Only a few percent shift of all formant frequencies, either toward the high-frequency region or toward low frequency, from the original values has been found to lose the voice individuality almost 100% while pitch frequency does not. Pitch frequency has been found to be far more robust than the formants. A few percent shift of pitch frequency has no damage on the individuality. To lose the individuality it is necessary to change the pitch frequency by as much as 50% or more toward either the high- or low-frequency regions. [Work supported by The Sound Technology Promotion Foundation.]
Relationship between physical characteristics and speaker individualities in speech spectral envelopes
Authors: Kitamura Tatsuya , Akagi Masato
Published: October 2005

Significant physical characteristics for speaker identification in speech spectral envelopes of vowels were investigated by psychoacoustic experiments. Previous studies [T. Kitamura and M. Akagi, J. Acoust. Soc. Jpn. 16(E), 283–289 (1995)] showed that the speaker individualities in spectral envelopes of vowels mainly existed in higher frequency bands. In this study, the effect of the elimination of the spectral peaks and/or dips of spectral envelopes in the higher frequency band on speaker identification was investigated. Additionally, the frequency band with speaker individualities was specified in detail. The stimuli for the experiments were vowels resynthesized from their FFT cepstral data by using the log magnitude approximation (LMA) analysis–synthesis system. They were normalized pitch frequencies and power, and handled specific frequency bands of the spectral envelope. The experimental results lead to the following conclusions: (1) The peaks in the spectral envelopes were more significant than the dips for speaker identification; and (2) speaker individualities mainly exist in the frequency band above the peak around the 20 ERB rate (1740 Hz), and the voice quality can be controlled by replacing the frequency band of one speaker with that of another.
Detection of sentence prominence using voice source parameters
Authors: Ding W. , Campbell W. N.
Published: October 2005

The relation between sentence-level prominence and voice-source characteristics is investigated using shifting word focus in prepared dialogues of both English and Japanese from a female and a male speaker, respectively. The voice source was analyzed using a Rosenberg–Klatt model where the parameters include fundamental frequency (f0), amplitude of voicing (AV), open quotient (OQ), and spectral tilt (TL). The parameters were simultaneously estimated pitch synchronously from the speech signal by an ARX method. As a test of the estimation, electroglottograph (EGG) signals were also used to measure OQ pitch-by-pitch. The estimated parameters, including the ratio of glottal open phase to closed phase, were then compared with labeled prominence in the speech and a clear correlation found. Both the ARX analysis method and EGG-based measurements yield almost the same results for OQ estimation but the former is automatic and can be calculated from the raw speech waveform alone. A strong relationship between prominence and OQ and TL has been confirmed in these experiments, which extend previous work on the estimation of prominence from acoustic measures first reported in [W. N. Campbell, Proc. ICSLP 92, 663–666 (1992)].
Accurate three-dimensional sound reproduction over headphones using Toltec processing
Authors: Wightman Frederic L. , Tucker Timothy J.
Published: October 2005

Spatial hearing research suggests that the most salient of the acoustical cues which determine the apparent position of a sound image are the interaural difference in time-of-arrival of the sound at a listener’s two ears and the filtering of the sound by the listener’s pinnae. An accurate virtual auditory space can be created by assuring that each sound source present in the space produces, at the listener’s eardrums, the interaural delay and spectral cues appropriate to the intended position of the sound. If headphones are used to produce the sounds, synthesis of a virtual source can be accomplished by convolving the source signal with a left–right pair of filter impulse responses. Each filter includes a delay, a pinna filter that is appropriate to the desired source position, and compensation for the headphone characteristics. The fidelity of the resulting virtual auditory space depends critically on the similarity of the pinna filters used in the synthesis and the listener’s own pinna filters. A currently available wireless consumer 3-D audio device incorporates listener matched pinna filters to render Dolby surround sound over headphones. Thus, the user hears sound from five locations exactly as if listening to a conventional home-theater system.
Characteristics of pitch extraction by ACLOS (AutoCorrelation of LOg Spectrum)
Authors: Kunieda Nobuyuki , Shimamura Tetsuya , Suzuki Jouji
Published: October 2005

A new pitch extraction method named ACLOS (AutoCorrelation of LOg Spectrum) [Kunieda et al., ICASSP-96, pp. 232–235 (1996)] is proposed. In this method, the fundamental frequency is estimated from the maximuum peak of the autocorrelation function of the log spectrum. ACLOS gives more robust and reasonable pitch information than other methods give. Quantitative evaluation of pitch extraction, however, has not been carried out. This paper presents a comparative performance of pitch extraction by ACLOS, the autocorrelation method, and the cepstrum method based on the assessment method employed by Rabiner [Rabiner et al., IEEE Trans. Acoust. Speech Signal Process. ASSP-24, 399–418 (1976)]. In order to increase the robustness for noisy speech, ACLOS is modified. Clipping of the log spectrum before calculating the autocorrelation function is introduced, because noise remarkably affects the valley of the log spectrum in low SNR. Experimental results reveal that ACLOS can reduce the gross pitch error even if the speech signal is degraded by noise. Conclusively, it is indicated that ACLOS will be a powerful tool for pitch extraction of noisy speech.
Estimation of fracture speed for Arctic ice-induced acoustic events
Authors: Stamoulis Catherine , Dyer Ira
Published: October 2005

The estimation of source parameters such as peak frequency, Doppler shift, and fracture speed is fundamental in the study of radiation from ice motion processes in the central Arctic. For this purpose, a population of acoustic events from the SIMI experiment data was analyzed, and fracture parameters estimated in the frequency range between 10 and 350 Hz. Both low- and midfrequency events, i.e., with peak frequencies below 100 Hz and between 100 and 350 Hz, respectively, were detected. For each event, the Doppler shift was first obtained through cross correlation of the event spectra at hydrophones of the receiving array. This was subsequently used to determine the fracture speed, assuming both horizontal and vertical motion. In the case of ice fracture, the latter is the rupture propagation speed, the upper bound of which is the Rayleigh wave speed. Previously (Chen, 1990), this value (approximately 1700 m s−1 for sea ice) has been assumed as the fracture speed. The present analysis shows that for the detected events, the fracture speed is considerably lower, specifically, between approximately 100 and 800 m s−1. This result suggests that ice fracture details affect significantly the propagation speed. [Work supported by ONR, Seismo-Acoustic Remote Sensing of the Arctic Environment.]
Effects of absorptivity due to fish on transmission loss in shallow water
Authors: Diachok Orest
Published: October 2005

Absorption losses of up to about 10 dB at night and 25 dB at twilight at the resonance frequency of pelagic fish, at a range of 12 km were observed during MODAL LION, a multidisciplinary experiment designed to test the feasibility of isolating biological scattering from other effects on long-range propagation at a relatively shallow (83 m) site in the Gulf of Lion. Comparison of measurements with a theoretical model that incorporates absorption layers in the water column permitted estimation of the average fish length (or bladder size), the number of fish/m3, and the depth of the layers. Good agreement between estimated parameters and echosounder and direct sampling results suggests the possibility of long-term tomographic mapping of fish parameters over large areas.
Motion compensated image reconstruction and holographic Doppler velocimetry using an encoded wavefront
Authors: Tamura Yasutaka , Nawa Masateru , Akatsuka Takao , Ishihara Chiaki
Published: October 2005

In this paper, an image reconstruction method for relatively moving targets with acoustical holography or a synthetic aperture focusing technique is proposed. A high-speed imaging system using transmitting pulses modulated with a system of Walsh functions was proposed by the authors. The method, which utilizes multiplex transmission, is called encoded wavefront transmission. Moving targets are simultaneously observed with a multiple transmission of pulses modulated by the Walsh functions. For each repetition period, a 3-D image is reconstructed. From a sequence of the reconstructed images, the relative velocity is estimated. Then the images are combined to a single motion compensated image. In the paper, the influence of the quantization of delay on the quality of reconstructed images is discussed. Allowable errors of velocity estimation are evaluated using computer simulations. Also discussed are the velocity vector estimation algorithms and the feasibility of this method to a ‘‘Holographic Doppler Velocimetry,’’ which visualizes the spatial distribution of the velocity vector. The experimental results demonstrate the ability of the method for a simple moving object.