bluuebunny/crossref_metadata_2025 huggingface dataset:
Aural classification of impulsive-source active sonar echoes
Authors: Pitton James , Philips Scott , Atlas Les , Ballas James , Brock Derek , McClimens Brian , Miller Maxwell
Published: October 2013

The goal of this effort is to develop automatic target classification technology for active sonar systems by exploiting knowledge of signal processing methods and human auditory processing. Using impulsive-source active sonar data, formal listening experiments were conducted to determine if and how human subjects can discriminate between sonar target and clutter echoes using aural cues alone. Both trained sonar operators and naive listeners at APL-UW were examined to determine a baseline performance level. This level was found to be well above chance for multiple subjects in both groups, validating the accepted wisdom that there are inherent aural cues separating targets from clutter. In a subsequent experiment, feedback was provided to the naive listeners and classification performance dramatically improved, demonstrating that naive listeners can be trained to a level on par with experts. Using these trained listeners at APL-UW, a multidimensional scaling (MDS) listening experiment was designed and conducted. The results of these experiments and an analysis of the data, particularly its correlation with the physical attributes of target and clutter echoes (i.e., signal features), will be presented.
Dolphin pods of the Southern California Offshore Range: Localization and behavior
Authors: Kim Katherine H. , Hursky Paul , Porter Michael B. , Hildebrand John A. , Henderson E. Elizabeth , Wiggins Sean M.
Published: October 2013

The Southern California Offshore Range, a U.S. Navy training area located near San Clemente Island, is rich in odontocete activity. Pods of dolphins, numbering as many as several hundred individuals, regularly transited the area and frequently vocalized during the 2004 SCORE 23F experiment. Such acoustic data were collected on a high-frequency, four-element, horizontal line array as well as on a high-frequency, single-element buoy. The copious dolphin vocalizations were then processed using automated whistle and click detection techniques and various localization methods which utilized time-of-arrival differences, frequency-domain beamforming, and multipath arrival structure. Combining the acoustic tracking results with concurrent visual observations provides a unique look at large numbers of free-ranging dolphins at and below the sea surface and suggests certain group behavioral patterns.
Acoustic analysis for the Haro Strait on 5 May 2003
Authors: Fromm David M.
Published: October 2013

On 5 May 2003, USS SHOUP conducted sonar training for 4 h while transiting through the Strait of Juan de Fuca and the Haro Strait. During the time period when the sonar was configured for long-range operations, the transmissions were alleged by some observers to have influenced the behavior of the resident J-pod of orcas. Additionally, the transmissions were received and recorded on various hydrophones deployed for monitoring marine mammal vocalizations. The U.S.-Navy-commissioned detailed reconstruction of the event that relates the location of SHOUP, the J-pod, and the monitoring hydrophones during the time period of SHOUP’s long-range sonar operations is presented. By combining high-fidelity predictions of the acoustic field with the in situ acoustic recordings, the reconstruction provides a detailed, moment-to-moment picture of the worst case estimates of the sonar sound levels experienced by the J-pod. [Work supported by the U.S. Navy Pacific Fleet.]
Background noise reduction of manatee vocalizations
Authors: Yan Zheng , Cattafesta Louis N. , Niezrecki Christopher , Beusse Diedrich O.
Published: October 2013

The West Indian manatee (Trichechus manatus latirostris) has become an endangered species in the United States partly because of an increase in the number of collisions with boats. A device to alert boaters of the presence of manatees is desired. Previous research has shown that background noise limits the detection range (which is critical for practical implementation). By improving the signal-to-noise ratio of the vocalization signal, it is possible to extend the detection range. The finite impulse response (FIR) structure of the adaptive line enhancer (ALE) can detect and track narrow-band signals buried in broadband noise. In this paper, a constrained infinite impulse response (IIR) ALE, called a feedback ALE (FALE), is implemented to reduce the background noise. In addition, a bandpass filter is used as a baseline for comparison. A library consisting of 100 manatee calls spanning ten different signal categories is used to evaluate the performance of the bandpass filter, FIR-ALE, and FALE. The results show that the FALE is capable of reducing background noise by about 6.0 and 21.4 dB better than that of the FIR-ALE and bandpass filter, respectively, when the signal-to-noise ratio (SNR) of the original manatee call is −5 dB.
Simulation of ranges for acoustic-based manatee detection
Authors: Niezrecki Christopher , Gur Berke M. , Cramer James , Beusse Diedrich O.
Published: October 2013

One aspect of the feasibility of an acoustically based manatee detection system relies upon the distance in which a manatee vocalization is detectable. The magnitude of environmental noise, manatee vocalizations, as well as the acoustic spreading properties of the habitat need to be considered to estimate the detection range of a vocalizing manatee. The simulation presented combines measured source levels of manatee vocalizations with the modeled acoustic properties of manatee habitats to illustrate the effective ranges in which manatees are detectable. The simulation indicates that background noise significantly affects the detectable range.
The role of cavitation in therapeutic ultrasound
Authors: Crum L. , Bailey M. , Khokhlova V. , Sapozhnikov O. , Rabkin B. , Evan A. , McAteer J. , Pishchalnikov Y. , Williams J. , Cleveland R.
Published: October 2013

Ed Carstensen has made many contributions to biomedical ultrasound but among those that are becoming more and more relevant to current clinical practice are those that determine the conditions under which cavitation is induced in vivo. For many years, it was assumed that the medical ultrasound devices were unable to induce cavitation in living tissue because either the acoustic conditions were not sufficient or the nucleation sites that are required were too small. With the advent of lithotripters and high-intensity focused ultrasound (HIFU) devices, cavitation generation in vivo is commonplace. Our current research at the University of Washington has focused on the role that cavitation plays in stone comminution and tissue damage during lithotripsy, as well as the enhancement or reduction of desirable coagulative necrosis during HIFU application. During HIFU application, we find enhanced heating that results from nonlinear acoustic wave propagation (a key Carstensen contribution) leads to vapor bubble formation. This presentation will review our recent studies in this area. [Work supported in part by the NIH under CA109557 and DK43881, and the NSBRI SMS00402 under NCC9-58-50.]
Risk factors for tissue injury induced by shock wave lithotripsy (SWL)
Authors: Evan Andrew P. , Willis Lynn R. , Connors Bret A. , Blomgren Philip M. , Handa Rajash , Shao Youshi , McAteer James A. , Pishchalnikov Yuri A. , Lingeman James E.
Published: October 2013

A clinical dose of SWL consistently and specifically disrupts the cellular layers of renal veins and arteries, first in the medulla, but progressing into the cortex with an associated inflammatory response. The resulting hemorrhage within the focal zone produces regions of intraparenchymal and subcapsular hematomas of varying size. Renal blood flow and glomerular filtration rate fall acutely by 50% in the treated kidney and by 20% in the untreated kidney. The sites of acute injury form scars with a permanent loss of renal function and have been associated with apatite/brushite stone formation and hypertension. Our team has shown that the size of the SWL-induced lesion can be dramatically reduced by lowering the kV level, applying fewer shock waves, slowing the shock wave rate, and by pretreating the kidney with 100–500 shock waves at 12 kV prior to standard SWL. The mechanism of tissue injury caused by SWL has not been defined; however, protocols that reduce cavitation activity also reduce the size of the SWL-induced lesion, and injection of bubbles into the renal vasculature, which support cavitation, intensifies and broadens the regions of the SWL-induced injury.
Numerical study on nonlinear behavior of a collapsing bubble cloud in an ultrasound field
Authors: Yoshizawa Shin , Ikeda Teiichiro , Takagi Shu , Matsumoto Yoichiro
Published: October 2013

Cloud cavitation is known well as one of the most destructive cavitations. High pressure generated by the violent collapse of a bubble cloud causes severe erosion, noise, and vibration in hydraulic machines. In the medical field, many researchers have investigated the behavior of the collapsing bubble cloud to effectively use the highly concentrated energy for HIFU (high-intensity focused ultrasound) applications. In this study, it is assumed that the acoustic cavitation forms a spherical bubble cloud which consists of many microbubbles, and ultrasound focusing in the spherically symmetric cloud is numerically investigated. The compressibility of the liquid, the evaporation and condensation of the liquid at the bubble wall, and heat transfer through the bubble wall are considered in the simulation. The pressure wave focuses to the center of the cloud and the pressure inside bubbles extremely increases when the frequency is near the first mode natural frequency of the cloud. Especially in the cases of relatively high-pressure amplitudes, a shock wave is formed in the cloud and it generates high pressure fluctuation near the center of the cloud even when the frequency is much lower than the first mode frequency.
Piezocomposite array technology for commercial and military sonar applications
Authors: Doust Barry J. , Pazol Brian G.
Published: October 2013

Piezocomposites are a widely known form of piezoceramic with proven advantages over conventional monolithic piezoelectric ceramics providing improved efficiency and bandwidth. Unique manufacturing processes such as injection molding, curved structures, and layered array assembly provide creative solutions to complex, state-of-the-art designs. In addition, recent advances in piezocomposite technology have addressed the optimization of materials and electroacoustic design to provide devices with improvements in bandwidth and transmit power capability. Several state-of-the-art designs will be presented showing capability of producing complex-shaped transducers and arrays for transmit only, receive only, and two-way (transmit/receive) applications. These commercial and military systems will be presented showing the unique operational capability achieved using curved array structures, unique aperture patterns, and precisely matched phased arrays. Application examples will be presented highlighting communication and navigation, imaging, and parametric systems.
Modal acoustic transducer array
Authors: Butler John L. , Butler Alexander L.
Published: October 2013

An acoustic system composed of an array of transducers, which generates multiple acoustic radiation modes, is presented and shown to yield directional steered beam patterns when the modes are appropriately combined together. A single ring array which uses eight piston transducers with a common tail mass and a cylindrical array of five of these rings are used to illustrate the performance of such a modal acoustic array. A discussion of the operation of the transducer array with a common tail mass as well as the means for combining the modes is presented. Monopole, dipole, and quadrupole array modes are illustrated with finite-element models. These modes are then combined together to generate a true cardioid, a new very wide cardioid type, and a low sidelobe narrow caridioid-type beam pattern. Calculated and FEA results are compared with measurements. [Work supported by ONR.]
Characterization of an underwater electroacoustic transmit system and the use of real electrical equivalents circuits for approximating loaded projectors
Authors: Bachand Corey L. , Brown David A.
Published: October 2013

Many underwater applications using acoustic communication rely upon an effective and efficient system of transmit hardware for adequate signal strength, bandwidth, and long-term sustainability. The focus of this work is to outline a procedure for investigating and optimizing the performance of transmit hardware intended for broadband underwater communication. The transmit hardware considered in this discussion consists of a power supply, power amplifier, matching (step-up) transformer, tuning inductor, and loaded piezoelectric projector. The use of an electrical equivalent circuit of a piezoelectric projector is adopted for performing complex power measurements throughout the transmit hardware for system characterization. Parameters for constructing an electrical projector circuit can be obtained analytically or experimentally. The complex power measurements are automated with a digital function generator and digitizing oscilloscope under software control. This method allows developers to evaluate the performance of the transmit hardware under realistic operating conditions in an engineering laboratory with standard equipment. One particular transmit hardware configuration, the WHOI Micro-modem, will be used to demonstrate the testing method.
Electrokinetic acoustic transducer
Authors: Chotiros Nicholas P.
Published: October 2013

An electrokinetic (EK) transducer consists of a liquid-saturated porous solid with electrodes at each end. It converts a pressure difference into electrical potential by means of the naturally occurring electrical charge that exists at the interface between certain liquids and solids. In 1964, Collins and Ellis [‘‘Electrokinetic, acoustic pressure transducer,’’ J. Acoust. Soc. Am. 36, 1858–1860 (1964)] published a paper describing a prototype EK acoustic pressure transducer, based on a very simple formula for the EK potential. In 1965, Rice and Whitehead [J. Phys. Chem. 69(11), 4017–4024 (1965)] published a more elaborate theoretical model of EK flow in a narrow capillary. Although the EK transducer had been presented as a pressure transducer, it is essentially a pressure difference transducer. This paper explores its potential in the light of Rice and Whitehead and later publications. [Work supported by the Office of Naval Research, Ocean Acoustics.]
Wave propagation in liquid-filled tubes: Measurements and model predictions
Authors: Kyle Aaron M. , Wodicka George R. , Ordóñez Sandra L. , Juan Eduardo J. , Bolton J. Stuart
Published: October 2013

Wave propagation in liquid-filled pipes was investigated using time- and frequency-domain techniques. Water- and ethanol-filled copper and PVC pipes having inner diameters of 1.44 and 1.19 cm, and wall thicknesses of 0.0686 and 0.208 cm, respectively, were driven with tone bursts from a submerged hydrophone, and the resultant acoustic pressures in the liquid were measured. Group velocities in the copper pipe were observed to decrease with increasing frequency: velocities were 1124 m/s at 10 kHz and 1039 m/s at 50 kHz in water and 1052 m/s at 10 kHz and 902 m/s at 40 kHz in ethanol. Propagation in the PVC pipe was significantly slower, e.g., the estimated water group velocity at 10 kHz was 593 m/s. The estimated group velocities were then compared to those predicted by an acoustic transmission line model of the pipes. The predicted group velocities were within 13% of the estimated values for the copper tube for both liquids. The pipe systems were also excited with Gaussian noise, and exhibited bands of low spectral energy that could be attributed to the transverse resonances of the tube walls. The model predicted the upper frequency limit of these bands to within 5% of measured values.
Global active control of broadband noise from small axial cooling fans, Part 2
Authors: Green Matthew , Sommerfeldt Scott
Published: October 2013

The multi-channel filtered-x LMS algorithm has previously been used for feed-forward control of the tonal noise of a small axial cooling fan [Gee and Sommerfeldt, ‘‘Application of theoretical modeling to multichannel active control of cooling fan noise,’’ J. Acoust. Soc. Am. 115, 228–236 (2004)]. With much of the tonal noise content removed it becomes desirable to reduce the broadband fan noise. A previous study demonstrated the feasibility of achieving desirable broadband attenuation by means of active feedback control. Measurements will be presented and discussed that have an impact on the control achievable. Experimental control results will be presented.
Band gap engineering for three-dimensional periodic systems of air bubbles in water
Authors: Kushwaha Manvir S. , Djafari-Rouhani Bahram , Dobrzynski Leonard
Published: October 2013

Systematic and extensive evidence for the existence of multiple, complete, huge stop bands in the band structure for three-dimensional (3D) cubic arrays of air bubbles in water is reported. A Fourier series expansion method, which does not require matching of the messy boundary conditions, is used to investigate all three important 3D geometries such as face-centered cubic (fcc), body-centered cubic (bcc), and simple-cubic (sc) arrangements. The lowest stop bands are largest for a volume fraction f≤10%, with a gap/midgap ratio of ≊1.8 for all three geometries. Surprising but rigorously justifiable is the fact that the low-frequency flat passbands for the perfectly periodic systems correspond to the discrete modes of a single bubble. This is an artifact of the low-filling fraction and huge density contrast in air and water. It is emphasized that such a simple inhomogeneous system made up of air bubbles in water can exhibit the widest stop bands ever reported for elastic and/or dielectric periodic composites.
Unconventional thermoacoustic heat engines
Authors: Hilt Matthew G. , Pestka K. A. , Mahan G. D. , Maynard J. D. , Pickrell D. , Na B. , Tamburini J.
Published: October 2013

During 1988 to 1994, John Strachen and Harold Aspden demonstrated an all-solid-state thermoelastic cooler which was 0.5 cm thick and a few centimeters in length. With 7.2 V dc applied across the device, it drew 6.3 W of electrical power and produced 13.7 W of cooling power with a 20°C temperature drop. The coefficient of performance was 2.2, or 21% of the maximum possible (Carnot) efficiency. The device operated reversibily; 3.7 W of heat throughput generated 0.15 W of electrical power, for an efficiency of 47% of Carnot. The device operated at a frequency of about 500 KHz. To date, no one has found an explanation for the effect. Recently we have begun a program to develop a theory and to reproduce a working device. This research, as well as some research with other unconventional thermoacoustic devices, will be presented. [Research supported by DARPA and the Aviation and Missle Command.]
An open-air infrasonic thermoacoustic engine
Authors: Slaton William
Published: October 2013

Wind noise at infrasound monitoring stations is a significant problem especially at the low frequencies of interest. Noise-reducing filters, typically consisting of radial arrays of porous hose, effectively area average the infrasonic pressure wave over a large space. The resulting area-averaged sound wave is then measured by a microbarometer. However, the only method to calibrate both the microbarometer and wind-noise filter is to use atmospheric or land-based man-made explosion. Thus, an infrasound source is needed that can calibrate both the microbarometer and the wind-noise filters in a safe way. A lowfrequency open-air thermoacoustic prime mover in a Helmholtz resonator has been constructed to fulfill this purpose. The system resonates at 10 Hz, is portable, compact, and safe to operate. The engine’s experimental and theoretical performance will be presented. [Work supported by a subcontract with the National Center for Physical Acoustics and a grant from the University Research Council at the University of Central Arkansas.]
Hot wire anemometry for the measurement of temperature and velocity fluctuations inside a thermoacoustic cooler
Authors: Berson Arganthaël , Blanc-Benon Philippe , Mongeau Luc , Paek Insu
Published: October 2013

Hot wire anemometry was used to measure velocity and temperature fluctuations inside a thermoacoustic refrigerator. In an oscillating flow with zero-mean velocity, such as in an acoustic standing wave, heat transfer is different from heat transfer in a steady flow. A dynamic calibration of the system is required. This calibration was done inside the resonator of the cooler, with no stack and no heat exchangers. Two thermoacoustic systems were studied to calibrate the anemometer in air at atmospheric pressure and in He/Ar mixtures at a mean pressure of 6 bars. Measurements of temperature and velocity were done at the end of the stack and heat exchangers. Correlations between temperature and velocity fluctuations were obtained, and the enthalpy convective flux was computed. These results were compared with results obtained from numerical simulations recently done at Ecole Centrale de Lyon [D. Marx, AIAA J. 42(7) (2004)].
Attending to auditory events ‘‘takes’’ time...event time
Authors: Jones Mari R.
Published: October 2013

Commonplace acoustic stimuli in our environment unfold in time over many time scales, ranging from milliseconds to seconds to minutes. At each time level, there is some ability to perceive and/or ignore stimulation. What does this mean for the role of attention? I suggest that auditory attention takes time, but not necessarily processing time. Instead, moment-to-moment attending literally takes hold of (i.e., locks into) event time spans by entraining to event time at one or more levels. Efficient attending involves an internal activity (a pulse of attentional energy?) that is capable of coordinating in time with an unfolding sound pattern such that attending energy coincides with to-be-attended elements. My main hypothesis is that, to attend efficiently at any time scale, synchronicity of attending with constituent sound elements is a necessary, but possibly not a sufficient, condition. I unpack this idea using illustrative dynamical models that assume an entrainment approach to attending. Several experiments use auditory sequences in which the time structure of constituent tones is systematically varied. In some tasks, listeners judge standard and comparison time intervals in different rhythmic contexts; in others, they identify the pitch of probe tones in sequences where both pitch and time structure vary.
Selective attention with ambiguous dichotic-pitch images
Authors: Bilsen Frans A.
Published: October 2013

Experiments in the past have shown that several types of dichotic pitch arise from dichotic white noise stimuli having a particular interaural phase relation [e.g., F.A. Bilsen and J. Raatgever, compact disc ‘‘Demonstrations of Dichotic Pitch,’’ Delft University of Technology (2002)]. Often such stimuli generate two or more ambiguous images inside the head at different places along the lateralization axis, each image having the same or a significantly different pitch value. Which pitch at which place is heard is a matter of selective attention. Typically, only one image can be heard at a time (ambiguity of place coupled with pitch). New experiments on dichotic repetition pitch will be reported that show the existence of a continuum of different pitches for one parameter setting of the stimulus. Which pitch is perceived depends on the lateralized position of the focus point of attention by the listener. Implications for the organization of the binaural auditory scene and the process of selective attention will be reviewed.
Frequency-band importance functions for auditory and auditory-visual speech by hearing-impaired adults
Authors: Grant Ken W.
Published: October 2013

How we listen to speech appears to be fundamentally different in a number of respects when we can simultaneously see the face of the speaker while listening to his or her speech. Not only is our ability to recognize and understand speech far better when we can see as well as hear, as compared to hearing alone, but the way we hear is also different. This is evident in the patterns of activity in primary auditory cortex, which are different for auditory versus auditory-visual speech inputs, as well as data from normal-hearing subjects suggesting that auditory attention is focused on different spectral regions depending on whether visual speech cues are available. The present study examines whether frequency band-importance functions are different for auditory and auditory-visual speech recognition in a group of hearing-impaired listeners. Results show that hearing-impaired listeners perform much like normal-hearing subjects in attending to primarily low-frequency speech cues under auditory-visual conditions. In contrast, under auditory-alone conditions, hearing-impaired listeners place more importance on mid-to-high-frequency acoustic information, presumably to better recognize place of articulation cues.
Acoustic scattering of fluid-filled spheres: Modeled and experimental results
Authors: Deveau David
Published: October 2013

Investigation into the scattering nature of surfaces or other physical objects often requires the use of measurement systems which cannot always be well controlled. This lack of control can be compensated for by calibrating the resulting measurements against a known target. While these targets can be any object, the goal is to use a target that has a stable scattering response and is independent of angle. The ideal shape is that of a sphere but even this can be improved with the addition of internal fluids that focus and temperature stabilize the scattering response. A scatter response model of a sphere has been developed and used to design four thin-walled spheres, each with a different diameter and filled with a focusing fill fluid (Fluorolube). One pair of spheres was measured in an ocean environment while the second pair was tested in a controlled test tank from 5–120 kHz but using shorter continuous wave pulses. While the ocean-measured spheres closely matched the model, the test tank measurements provided insight to the model’s near-field limitation and low-frequency noncontinuous wave effects.
Liquid-filled focusing cylinders and the caustic merging transition
Authors: Dudley Christopher , Marston Philip L.
Published: October 2013

Thin spherical shells filled with a liquid having a sound speed significantly less than the speed of sound in water are widely used for targets having enhanced backscattering. This enhancement has been analyzed using quantitative ray theory [P. L. Marston, Phys. Acoust. 21, 1–234 (1992)]. Backscattering enhancements are investigated here for a liquid-filled flat-ended thin fiberglass circular cylindrical shell in water. In addition to partially focused enhanced backscattering for near-broadside illumination, this target exhibits enhancements for specific ranges of tilt angles associated with caustic merging transitions previously demonstrated for blunt plastic cylinders [F. J. Blonigen and P. L. Marston, J. Acoust. Soc. Am. 107, 689–698 (2000)]. The refractive properties for the tilted cylinder depend on the effective refractive index N that is a function of the tilt angle and the actual acoustic refractive index of 1.68 (relative to water) for the enclosed liquid. Backscattering enhancements are visible from the tilted cylinder associated with two- and four-chord transmitted internally reflected rays when the tilts are such that N is close to 2 and is close to 4, respectively, as predicted by ray theory. The wave-number-radius product was as small as 16. [Work supported by the Office of Naval Research.]
Combining an energy boundary element analysis with an energy finite element analysis for computing airborne noise inside a flexible structure due to an exterior acoustic source
Authors: Zhang Geng , Vlahopoulos Nickolas
Published: October 2013

The energy boundary element analysis (EBEA) has been utilized in the past for computing the exterior acoustic field at high frequencies (above ∼400 Hz) around vehicle structures and numerical results have been compared successfully to test data [Wang et. al., J. Sound Vib. 126, 278–283 (2004); Internoise (2002)]. The EFEA has been developed for computing the structural vibration of complex structures at high frequencies and validation has been presented [Zhang et. al., J. Sound Vib. 282, 679–700 (2005); 41, 11–12 (2005); Finite Elements Anal. Des. 41(11-12) (2005); Wang et. al., SAE Paper No. 2005-01-2372]. In this presentation the EBEA is utilized for computing the acoustic field around a cylindrical structure (similar to the NASA aluminum test-bed cylinder) from an external acoustic noise source. The computed exterior acoustic field comprises the excitation for the EFEA analysis. The structural vibration and the interior noise levels are computed, demonstrating how the EBEA and the EFEA can be combined in airborne noise applications for performing a complete vibro-acoustic analysis. [Work supported by ONR Code 334, SBIR program.]
The effect of in-plane forces on sound radiation from convected fluid-loaded plates
Authors: Schmidt Peter L. , Frampton Kenneth D.
Published: October 2013

It is well established that fluid flow can have significant effects on structural acoustic behavior, along with the fact that induced coupling between discrete modes of vibration becomes significant as flow velocity increases. Work in this area has been confined to flows in air, over unloaded structures, with the effects on sound radiation efficiency, kinetic energy, and sound power radiation quantified and compared for various flow speeds. The purpose of this work is to study the effects that plane stress has on these structural acoustic phenomena. Theoretical development of the equations governing the vibration of a simply supported plate subjected to in-plane forces in an infinite baffle and an aerodynamic system that models a semi-infinite flowing medium along with the method for coupling these systems is included. Computational results are presented illustrating the behavior of the uncoupled coupled effects on the sound power radiation from the plate in both subsonic and supersonic flows, for a variety of loading cases.
Decompostion of the time reversal operator applied to detection and focusing in a 12-m-deep channel in Brest Bay
Authors: Prada Claire , De Rosny Julien , Clorennec Dominique , Minonzio Jean-Gabriel , Fink Mathias , Bernire Lothar , Hibral Sidonie , Billant Philippe , Folgot Thomas
Published: October 2013

We have developed a 12-kHz, 24-element rigid source receiver array [J. Acoust. Soc. Am. 117, 2462 (2005)]. During sea trials in spring 2005, the array has been deployed in the Brest Bay, in a 12-m-deep channel. Backscattered data from a variety of submerged objects have been recorded for distances up to 1 km. After the description of the experimental setup and the acoustic propagation conditions, results from detection experiments using the DORT method will be presented. In particular, we will focus on separation of target echo from bottom reverberation as well as separation of two targets. Resolution and sensitivity aspects of the method will be discussed and compared with results obtained with conventional beamforming. Furthermore, selective focusing by transmission of the eigenvectors of the time reversal operator will be shown. [Work supported by the French DGA/SPN under Contract No. 02 77 154 00 470 75 53.]
Reverberation time, mean-free-path, and sound absorption in concert halls—Numerical examination by computer simulation
Authors: Hidaka Takayuki , Nishihara Noriko
Published: October 2013

Sabine and Eyring equations are commonly used to estimate the reverberation time (RT) in concert halls. Derivations of the two equations are based on well-defined and different physical assumptions, and they are both slightly different from the realistic situation in halls. In many researches so far, comparatively simple room shape has been utilized to study the question of which equation is preferable. In this study, the sound fields in rooms with more complex or wide-ranging shape are numerically analyzed by applying the computer simulation technique and CAD models for architecture. Focusing on the fundamental relation between the mean free path as a physical measure of the room and the RT, validity of the two equations in actual halls is discussed. Next, the influence of the room shape or the choice of the RT equation on the effective sound absorption is examined.
An electronic windscreen for microphones
Authors: Elko Gary W. , Meyer Jens
Published: October 2013

Wind-noise pickup in microphones can be highly disturbing, especially for directional microphones that attain their directivity by using velocity or spatial derivatives of the acoustic pressure. Since small directional microphones are common in audio communications systems, the problem of wind noise is well known and the typical solution is to use a windscreen. Conventional windscreens that block the wind but do not significantly alter the sound field can be very effective, but need to be relatively large to attain a good reduction in wind-noise pick-up. Small directional microphone arrays are more commonly used in hearing aids since they have been clinically shown to improve hearing in noise for hearing-impaired users. Since hearing aids are required to be compact, an effective conventional windscreen is not practical. This talk describes a novel multi-microphone wind-noise reduction algorithm that we refer to as an ‘‘electronic windscreen.’’ This new algorithm and its variants have low computational cost and are therefore applicable to commercial digital hearing aids that use multi-microphone arrays to attain directionality.
Processing of vector fields in underwater waveguides
Authors: Rapids Brian R.
Published: October 2013

The ability to measure the scalar and vector properties of underwater acoustic fields has improved over the past decade with advancements in transducer technology. Investigations regarding the processing of such sensors have principally focused upon the exploitation of a vector sensor as a directional hydrophone and the ability to achieve significant spatial gains in an unusually small form factor (i.e., superdirectivity). These superdirective elements may then be examined in the framework of standard linear array processing techniques. Alternatively the scalar and vector sensors can be combined multiplicatively to generate estimates of the acoustic intensity vector. Several investigations regarding the detection of signals in noise with these multicomponent sensors have found that optimal linear processing produces a superior signal-to-noise ratio at the back end of the processor when compared to the intensity processor. While the intensity-based processing may not provide an optimal detector, it does provide insight into the fundamental nature of the underwater acoustic field by characterizing the energy flux density. This talk will discuss the effects of signal-model mismatch on the linear and multiplicative process by examining cases in which the assumed phase difference between pressure and particle velocity is not zero.
Acoustic source separation via particle velocity vector measurement
Authors: Teramoto Kenbu , Kahn M. D. Tawhidul
Published: October 2013

A novel blind source separation of a mixture of two or more voice signals has been proposed in the present paper. The separation system has been focused based on the spatio-temporal blind source separation algorithm. The proposed algorithm utilizes the linearity among the signals of sound pressure and the components of three-dimensional (x, y, and z directional) particle velocity, all of which are governed by the equation of motion. Principally, as the mechanism of blind source separation uses no a priori information about the parameters of convolution, filtering, as well as mixing of source signals, some simple assumptions such as the statistical independency of the linearly combined (mixed) observed signals containing zero mean as well as unit variance have been implied in the present separation algorithm. Therefore, the proposed method has successfully simplified the convoluted blind source separation problem into an instantaneous blind source separation problem over the spatio-temporal gradient spaces. An acoustic experiment with two female voices has been carried out to compare the simulated data as well. A Micro-Flown system has been adopted to evaluate the voice signals efficiently.
Statistical characterization of sonarlike clutter observed on the STRATAFORM during the 2003 Acoustic Clutter Experiment in the 400–1500-Hz region
Authors: Preston John R.
Published: October 2013

In 2003 ONR sponsored the Acoustic Clutter Experiment to study shallow-water scattering and clutter in the STRATAFORM area off New Jersey. Sources were bistatically received coherent pulses. The receiver was the five octave research array (used horizontally). The STRATAFORM has benign surface morphology but contains many subsurface features. MIT researchers have shown fish to be a primary source of the observed clutter and reverberation. K distributions, with their shape and scale parameters, are used to describe non-Rayleigh behavior. Statistical characterization is presented versus location. The ‘‘bandwidth’’ effect is shown where the shape parameter first decreases inversely proportional to bandwidth but then increases back toward the Rayleigh distribution at higher bandwidths. The shape parameter estimates for the 2003 data are well fit by an elongated patch model of Abraham and Lyons. It is shown that shape parameter estimates are about the same for the 2003 and 2001 data taken in the same area. The main differences between the data sets are that the typical scatter sizes/strengths seem to have increased. This is consistent with observations by Nero of NRL and by MIT researchers of higher and more concentrated fish populations observed in 2003. [Work supported by ONR Code 32, Grant N00014-05-1-0156.]
Phase effects in F0 discrimination and temporal fine structure
Authors: Oxenham Andrew J. , Micheyl Christophe
Published: October 2013

Pitch discrimination with only high-order (unresolved) harmonics is dependent on their relative phases and is thought to be based on the temporal envelope of the waveform after peripheral filtering. In contrast, when low-order harmonics are present, phase effects disappear, and pitch may be derived from the estimated frequencies of the individual resolved harmonics. The dichotomy between the envelope-based periodicity from unresolved harmonics and the temporal fine-structure (or spectrally) based estimates of individual frequencies from resolved harmonics forms the basis of the well-known two-mechanism theory of pitch. Recently, the early idea that listeners use temporal fine-structure cues in unresolved harmonics to estimate the overall F0 has been revived as a third intermediate mechanism to account for why accurate F0 discrimination, normally associated with resolved harmonics, can sometimes be achieved in conditions that produce phase effects. Here we show that it is not necessary to resort to a third mechanism. Instead, we show that the relative component phases affect the instantaneous frequency distributions in ways that could influence the coding of frequencies for individual, partially resolved, harmonics. Implications for the interpretation of temporal fine structure in pitch and other auditory functions, such as speech perception, are discussed. [Work supported by NIH R01DC05216.]
Dominance region for pitch at low fundamental frequencies: Implications for pitch theories
Authors: Moore Brian , Glasberg Brian , Aberkane Idriss , Pinker Samantha , Caldicot-Bull Candida
Published: October 2013

The dominant region for pitch was measured for complex tones with low fundamental frequency (F0=35 and 50 Hz). The tones contained 59 harmonics, added in cosine or random phase. The harmonics were split into two groups; group A containing harmonics 1-K and group B containing harmonics (K+1)-N. On each trial, two successive complex tones were presented. In one, the harmonics in group A were shifted down by deltaF0 and the harmonics in group B were shifted up by deltaF0. In the other tone, the shifts were in the opposite direction. The tones were presented in random order and the subject had to indicate which had the higher pitch. The pitch judgements followed the components in group B for small K and the components in group A for large K. The frequency corresponding to the middle of the transition region was taken as the center of the dominant region, fdom. The value of fdom varied markedly across subjects but typically corresponded to harmonic numbers above the 6th, for both phase conditions. Thus, the dominant harmonics were unresolved. These results indicate that resolution of individual harmonics is not the key factor determining the location of the dominant region. [Work supported by the MRC.]
Assessing the speech intelligibility index in Johns Hopkins Hospital
Authors: Kwon Philip , Busch-Vishniac Ilene , West James
Published: October 2013

Over the last few years we have gathered considerable amounts of data on the sound pressure levels present in Johns Hopkins Hospital in Baltimore, MD. These data provide information on levels versus location, frequency, and time of day. Using these data we have determined the SII in various locations of the hospital. Speech intelligibility is a key issue in hospitals because the vast majority of communication takes place orally. Further, the vocabulary used in hospitals includes a significant set of unusual words such as pharmaceutical names that are easily confused. Thus, an SII higher than required in an office environment is needed for clear speech communication in a hospital. Our results suggest that speech intelligibility is compromised by the noise present in the hospital.
Modulation interference in speech recognition by cochlear implant users
Authors: Kwon Bom Jun , Nelson Peggy B.
Published: October 2013

When listening to speech in a background masker, normal-hearing listeners take advantage of envelope fluctuations or dips in the masker (or the moments that the SNR is instantaneously favorable). Cochlear implant listeners, however, do not exhibit such ability. In a previous study [Nelson et al., J. Acoust. Soc. Am. 113, 961–968 (2003)], speech recognition performance with modulated maskers was similar or slightly worse than with a steady noise. Clinical observation indicates that implant listeners usually have more difficulty understanding speech in modulated backgrounds. In the present study, the recognition of IEEE sentences by Nucleus recipients was measured in a variety of backgrounds. In tightly controlled conditions via direct stimulation, performance is often substantially poorer with modulated backgrounds (the differences in score are as large as 20–30%), strongly indicating that they are subject to modulation interference [B. J. Kwon and C. W. Turner, J. Acoust. Soc. Am. 110, 1130–1140 (2001)]. A mixture of speech and modulated backgrounds might be perceived as one distorted signal, rather than two signals, compromising the identity of the speech, as perceptual segregation of signals is very challenging. A future implant system should incorporate a strategy to provide multiple input sounds without sacrificing the sound identity.
The acoustic consequences of time-dependent changes of the vocal tract shape
Authors: Story Brad
Published: October 2013

During singing or speech production, the human vocal tract is a nearly continuously changing conduit through which sound propagates. As the vocal tract shape changes, its resonance frequencies also continuously vary, shaping an excitation signal into a sequence of vowels and consonants. This presentation will focus on modeling the time-dependent movements of the vocal tract shape and their acoustic consequences. Based on data collected with MRI and x-ray microbeam techniques, a kinematic model of the vocal tract area function has been developed that allows for efficient specification of time-dependent cross-sectional area changes in an acoustic waveguide. When coupled with a voice source, the result is a basic simulation of the sound production process from which pressures and airflows are generated. The components of the model will be presented and then used to demonstrate some time-dependent relations between the vocal tract shape and resulting acoustic characteristics. [Work supported by NIH R01-DC04789.]
Faraday waves and ultrasonic foggers
Authors: Holt R. Glynn
Published: October 2013

Locally flat liquid interfaces that are periodically forced to vibrate above a threshold amplitude exhibit an instability to waves of finite amplitude and half the forcing frequency. These waves (first observed and explored by Faraday) self-organize into a variety of patterns depending on experimental parameters. When driven at sufficient amplitude they can become turbulent and result in the pinch-off of liquid droplets. A very brief review of the relevant theory will be followed by a demonstration of acoustically induced Faraday waves in a couple of particular geometries. At least one demonstration of a practical application of Faraday waves will also be shown.
Extraction of the Green’s function from ambient fluctuations for general linear systems
Authors: Snieder Roel , Wapenaar Kees
Published: October 2013

The extraction of the Green’s function of acoustic and elastic waves from ambient fluctuations is by now a technique that is theoretically well-described and that has successfully been used in different applications. We show theoretically that the principle of the extraction of the Green’s function can be generalized to a wide class of linear systems. These new applications include the diffusion equation, Maxwell’s equations, a vibrating beam, and the Schröedinger equation. For systems that are invariant for time-reversal it suffices to have sources of ambient fluctuations on a surface that bounds the region of interest. When the invariance for time-reversal is broken; as, for example, in the case of the diffusion equation or for wave propagation in attenuating media, one also needs sources of ambient fluctuations throughout the volume. This work opens up new opportunities to extract the Green’s function from ambient fluctuations that include electromagnetic fields in conducting media, flow in porous media, wave propagation in attenuating media, monitoring of mechanical structures, and quantum mechanics.
The propagation of sound in planetary atmospheres and its application to bolide detection
Authors: Williams Jean-Pierre , McEwan Ian
Published: October 2013

The behavior of sound (i.e., its radiation pattern and range of detectability) is characterized in the complex dynamical systems of the Venus, Earth, Mars, and Titan atmospheres as modeled by a global circulation model (GCM). Sound propagation is affected by the composition, structure, and dynamics of a planet’s atmosphere; therefore, a modular approach is adopted so that any hypothetical atmosphere with varying climatic conditions and gas composition can be accounted for. Using the GCM to determine the structure and dynamics of an atmosphere, the sound path is ray traced accounting for viscous, thermal, and molecular attenuation. As a specific application, we discuss the practicality of an in situ acoustic sensor as a method for direct measurement of bolide influx rates in planetary atmospheres. Bolides provide well-characterized, large magnitude, low-frequency sound sources that are common to all planetary atmospheres and should be remotely detectable by acoustic sensors. End-to-end comparisons between Venus, Earth, Mars, and Titan are made by modeling a typical large terrestrial event and the resulting sound propagation in each environment. [Work funded by the O.K. Earl postdoctoral fellowship.]