bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering from stratified sediments
Authors: Ivakin Anatoliy N.
Published: February 2014

There is a special class of volume perturbations, which exist within stratified media and can be described in terms of displacement of isosurfaces of these parameters. Scattering from marine sediments with such perturbations is considered using a unified approach to volume and roughness scattering [A. Ivakin, J. Acoust. Soc. Am. 103, 827 (1998)]. Discrete stratification (layering) is treated as a particular case of a continuous one, where interfaces between layers are replaced by additional (transition) layers with acoustical parameters smoothly dependent on the depth. In the unperturbed medium, the transition layers are flat, which gives a zeroth-order solution. In the first-order approximation, volume perturbations of the aforementioned class are proportional to vertical gradients of corresponding acoustical parameters in the unperturbed medium and to displacement (roughness) of the isosurfaces of these parameters within transition layers. Note that there are only smooth continuous volume inhomogeneities in these layers, that is, there is no real roughness scattering, which is controlled by discontinuity of the acoustical parameters at the interfaces. A new general model is presented, which gives the volume scattering strength as a function of the wave thickness of the transition layers. The model does not require the vertical correlation sclae of inhomogeneities to be small in comparison with the layer thickness. In the case of low frequencies, where the transition layers are thin in comparison with the wavelength, the model provides an exact transition to existing results for scattering from rough interfaces and, thus, naturally links volume and roughness mechanisms of seabed scattering at low and high frequencies within a unified approach. [Work supported by ONR.]
The acoustic design of the Concertgebouw, Amsterdam, and resolution of the hall’s early acoustical problems
Authors: Clements Pamela
Published: February 2014

From the outset, acoustical considerations were a driving force in the design of the Concertgebouw. Several halls were used as acoustical models, including the Tonhalle in Düsseldorf, the Leipzig Gewandhaus, and the concert room of the Felx Meritus Society in Amsterdam. When the Concertgebouw opened in 1888, however, it had acoustical problems: the newly formed orchestra struggled with the hall’s long reverberation time, and balance between brass and strings was difficult. Various remedies were tried, including potted plants to ‘‘soak up’’ the sound. The installation of the organ in 1891 was thought by some to make the acoustics worse. Between 1895 and 1900 the problems were gradually resolved. Orchestral balance was improved in 1899 when the orchestra platform was rebuilt to reduce the steepness of the risers. Other factors included the approach of the new conductor, Willem Mengelberg, improved performance standards, and the arrival of the late Romantics, particularly Tchaikovsky, in the repertoire. Happily this coincided with improved transportation that enabled newly enthusiastic audiences to fill the hall. The paper uses plans, photographs and other historical evidence to explore the intent of the acoustic design of the Concertgebouw, and its transformation from near failure to musical and acoustical success.
Target strength analysis in high fish densities using a probing split beam transducer
Authors: Ona Egil , Svellingen Ingvald
Published: February 2014

Unbiased measurements of the mean target strength are needed if the absolute fish abundance is to be measured. For most pelagic fish, this also requires direct target strength techniques to work in high-density situations. A probing, pressure stabilized split beam transducer has been lowered from the research vessel directly into dense herring layers in order to resolve a single target at short range. Specialized hardware has been used for single fish target tracking, from which data on target strength, target directivity, swimming speed and tilt angle are derived. The paper will focus particularly on calibration procedures for transducer depth performance, target-tracking methodology and on the monitoring of essential transducer movement parameters.
Vortex shedding characteristics of two cylinders with differing diameters
Authors: Sylemez Muhittin , Atlar Mehmet
Published: February 2014

This paper presents an experimental investigation of the vortex shedding characteristics of two circular cylinders with differing diameters in representing a simple riser configuration. The smaller of the two cylinders is located at varying positions around the circumference of the larger cylinder. Measurement of forces on the cylinders and the associated shedding frequencies are recorded and analyzed for five different flow velocities and orientations of the riser in the Emerson Cavitation Tunnel of Newcastle upon Tyne University. The Reynolds number corresponding to the test conditions varies from 9.64×104 to 4.82×105 for the large diameter of the cylinder and from 3.5×104 to 1.75×105 for the small diameter cylinder. The experiments were split into two distinct phases: the first was flow visualization using the hydrogen bubble technique and the second phase was force and shedding frequency measurements.
Crack location using nonlinear means applying modulation of ultrasonic pulses by cw vibration
Authors: Kazakov Vyacheslav V. , Sutin Alexander M. , Johnson Paul A.
Published: February 2014

Nonlinear wave modulation spectroscopy (NWMS) was recently introduced as a new tool in NDE. This technique employs the nonlinear interaction of ultrasound and vibration in the presence of defects. Vibration changes the contact area within a defect effectively modulating an ultrasonic wave sensing the defect. NWMS has high sensitivity to the presence of cracks and can be a very good tool for a ‘‘pass–fail’’ test but cannot provide the crack location. A new method for locating defects or cracks in a material, presented in this paper, is based on the modulation of ultrasonic pulses by vibration. The cw vibration induces modulation of the signal reflected from cracks. Measurements of the spatial distribution of the modulation level are the basis of nonlinear acoustic imaging. Experimental verification of the method has been conducted in steel plates containing a circular hole and a fatigue crack. The high-frequency (carrier) impulse was about 3 MHz, and the modulating vibration frequency was 5–15 Hz. This technique images a crack very well while a hole was not detected. As the location of damage is the next important issue in NWMS, this work represents an important step. [This work was partially supported by International Science Technical Center, Grant No. 1369.]
Functional imaging of temporal auditory processing
Authors: Griffiths Timothy D.
Published: February 2014

Functional imaging of the auditory system can be carried out using positron emission tomography (PET) and functional MRI (fMRI). Both techniques depend on the blood flow response to stimuli as a measure of brain activity, a process with a delay of 10 s in the auditory cortex. This limits the ability of the techniques to investigate temporal processing in the auditory system. Experiments to investigate the basis for temporal processing are critically dependent on the model that is used to interpret the brain blood flow data. The blood flow response in such experiments depends on local mean synaptic activity; this can be increased either by the firing rate in a subpopulation of cells or by increased synchronization of neural activity. At the millisecond level, an increase in the fMRI BOLD response with the temporal regularity of a signal at the millisecond level has been demonstrated as early as the cochlear nucleus. This may be due to an increased firing rate of onset chopper cells tuned to a particular autocorrelation delay or to increased synchronized activity in the whole population. The temporal processing of patterns over longer periods (seconds) is likely to involve areas of the cortex distinct from the primary auditory cortex.
Functional imaging of brain activity during speech production
Authors: Sidtis John
Published: February 2014

The functional anatomy of the cerebral cortex, subcortical nuclei, and cerebellum during speech production is understood primarily through the study of defects following brain damage. Functional imaging methods may provide another view of this system in normal as well as in impaired speakers. In the present study, 13 right-handed, native-English-speaking subjects performed a 60-s syllable repetition task during imaging of cerebral blood flow using positron emission tomography (PET). Each subject was scanned eight times (alternating speech and resting control conditions) and their repetitions of the syllables
Perception of English consonants from dynamic acoustic properties
Authors: Remez Robert E. , Piorkowski Rebecca L. , Wissig Stephanie , Batchelder Abigail
Published: February 2014

Phonetic perception is often said to depend on short-term attributes of vocally produced sound. Counterevidence to this premise is found in the example of sinewave replicas of speech. The dynamic properties of a sinewave replica evoke phonetic impressions despite the absence of typical or natural sounding short-term elements. To gauge the robustness of phonetic perception from dynamic acoustic properties, we compared identification performance by normal listeners across identification tests composed of signals that preserve dynamic properties of speech despite the absence of short-term speechlike properties: sinewave replicas modeled on the natural samples of 18 English consonants in CV syllables, noise-band vocoded signals derived from the natural samples, and chimerical signals exhibiting the coarse-grain spectrum envelope of natural speech and the fine structure of nonspeech signals. Identification from dynamic acoustic properties was well predicted from control performance using sampled natural speech in noise, showing that short-term acoustic properties and their corresponding auditory qualities are inessential in perceiving consonants. This outcome is consistent with a perceptual account that favors attention to the characteristic modulations of an acoustic carrier, and opposes an account appealing to auditory essences of each phonetic element.
Formant continuity and auditory scene analysis: The effect of vowel formant manipulations on the perception of synthetic nasal consonants
Authors: Harding Susan M. , Meyer Georg F.
Published: February 2014

The perception of a synthesized nasal /m/ changes to /n/ as the frequency of the second formant of a preceding vowel is increased when there are no transitions between the vowel and nasal; but /m/ is heard consistently when 20-ms transitions are introduced. A possible explanation is provided by auditory scene analysis: Formants of the vowel and nasal that are contiguous and close in frequency may be grouped using principles of similarity and good continuity into a single perceptual stream. Further experiments found a robust change in percept for prototype /n/ as well as /m/. Transitions from the vowel that conflict with the formant structure of the consonant also cause a similar change in percept for both nasal prototypes. The proximity of the second formant of the vowel to a formant in the nasal prototype is therefore unnecessary for the change in percept to occur; the presence of the vowel formant near to one of two target frequencies at the boundary with the nasal seems to be sufficient to determine the nasal percept and takes precedence over the structure of the nasal prototype. Thus, these results do not show strong evidence for auditory scene analysis applied to formants.
Sinewave speech/ nonspeech perception: An fMRI study
Authors: Liebenthal Einat , Binder Jeffrey R. , Piorkowski Rebecca L. , Remez Robert E.
Published: February 2014

Sinewave speech replicas follow the center frequency and amplitude of vocal tract resonances of natural speech but lack the attributes of vocal chord vibrations. They can be perceived as speech or nonspeech depending on expectation (Remez et al., 1981). Brain areas activated by sinewave replicas when perceived as nonspeech or as speech were compared with functional magnetic resonance imaging. In an auditory task, 30 nave subjects determined whether isolated second-tone formants were included in a following three-tones sinewave complex. The second-tone formant was either aligned (phonetic stimulus) or temporally reversed relative to the other tones in the complex (auditory stimulus). Halfway through the auditory task, subjects were informed about the phonetic derivation of the stimuli and trained to recognize the original speech. In a subsequent phonetic task, subjects identified sinewave stimuli containing the phoneme /p/. Following training, an increase in behavioral response time, concurrent with a decrease in left Heschl’s gyrus activation was observed specifically with the phonetic stimuli. This suggests automatic recognition of speech structure in the auditory cortex and interference with auditory processing of phonetic stimuli, acquired by training. In the phonetic task, the left inferior frontal gyrus was specifically activated implicating this area in phonetic processing.
Limits of sentence identification in gated and continuous noise
Authors: Nelson Peggy B. , Jin Su-Hyun , Earley Carney Arlene
Published: February 2014

Listeners with normal hearing sensitivity are able to take advantage of temporal dips in fluctuating noise. Their word identification in gated noise is better than identification in continuous noise. The limits of this ability are not well understood. Young adult listeners with normal hearing sensitivity were tested for their understanding of speech in gated and continuous noise at a variety of signal-to-noise ratios (SNRs) and gate frequencies from 2–32 Hz. Stimuli were digitized IEEE and CID sentences spoken by 10 talkers (5 male and 5 female). Pseudorandom noise was generated with the same long-term spectrum as the speech. Sentences were presented at an overall level of 65 dB SPL, with noise at +16-, +8-, 0-, −8- and −16-dB SNR. Listeners’ responses were scored for the number of keywords correct. Results showed that at −16-dB SNR of continuous noise, listeners were unable to repeat any keywords. Gate frequencies of 4 and 8 Hz resulted in the greatest keyword identification. Performance decreased at the slowest gate frequency for IEEE sentences and at fastest gate frequencies for all sentences. Results will be discussed in terms of listeners with hearing loss and cochlear implants. [Work supported by NIDCD.]
Processing of ultrasonic measurements for nondestructive evaluation of critical optical components
Authors: Meyer Alan , Candy James
Published: February 2014

Real-time nondestructive evaluation of critical optics in high-energy, pulsed laser experiments is crucial from a safety as well as maintenance viewpoint. Fluence levels in short pulse, high-energy lasers can produce pits and cracks in the surfaces of the lasers’ optical components. These flaws in the optical glass can adversely effect the production of the laser light or even result in a catastrophic failure of the optical component itself. Consequently, the identification and characterization of these flaws is critical. The production requirements of our target laser system mandate the automation of any inspection system. Consequently, it is necessary to develop an autonomous solution to process the reflected acoustic signals and, using this information, detect, localize, and characterize the optical flaws. In this paper we develop sophisticated signal and image processing techniques to automatically analyze laser-induced damage in optical glass. After preprocessing the raw channel measurement data from two orthogonal, narrow beamwidth, transducer arrays, a two-dimensional power image is created. A physics-based 2D matched filter is developed and used to detect and localize the flaws. An iterative solution is developed to sequentially search the resulting 2D image to extract and characterize the flaws.
Single snapshot array processing: The CLEAN algorithm applied to the pressure field
Authors: de Rosny J. , Song H. C. , Kuperman W. A.
Published: February 2014

The CLEAN algorithm, originally developed in radio astronomy [Astron. Astrophys. Suppl. 15, 417–426 (1974)] for intensity images, has been modified to process complex pressure signals. The iterative method allows one to find the position and strengths of a distribution of sources which are assumed to be grouped in small regions of the sky. Recently, we have applied the CLEAN algorithm successfully to matched field processing where the ambiguity surface corresponds to an image. The original CLEAN algorithm, however, is applied only to the field intensity (magnitude). In this paper, we apply the CLEAN algorithm to the complex pressure field received by a vertical array to enhance the matched field processing. This imaging method appears to be useful when just one or a few snapshots are available so that a reliable cross-spectral density matrix cannot be obtained. Numerical simulations will be presented for the modified CLEAN algorithm that extracts a weak source masked by a stronger source.
Matched-field processing in shallow water in the presence of internal waves
Authors: Stamoulis Catherine
Published: February 2014

The performance of matched-field processing algorithms in shallow water, in the presence of soliton packets, has been investigated through analysis of data from the SWARM95 experiment. In particular, acoustic data collected with a vertical array and a moving up-sweep source have been analyzed, in the frequency range 275–350 Hz. The source was placed below the surface mixed layer and its distance from the array varied between 2.5 and 27 km. Source localization using different matched-field algorithms has been performed, in order to assess the robustness of these processors in the presence of environmental mismatch and their degradation as a function of range. The primary result of the analysis is that these processors failed to localize the source accurately, even at the shortest range (2.5 km). Although broadband processing and inclusion of corrections for array tilt improved the results, the errors in source range (of the order of 1 km at short ranges and 5 to 10 km at long ranges) and depth remain significant. Alternative processing via mode filtering and subsequent matched-mode processing yielded more accurate results, particularly in cases were mode coupling was not an issue of concern.
Multitarget tracking using simulated annealing
Authors: Knobles David P. , Neilsen Tracianne , Koch Robert A.
Published: February 2014

It is common for passive detection systems to have multiple detections over a given time interval. The focus of this research is the simultaneous inversion for environmental parameters and the localization of multiple moving broadband sources in shallow water environments. Individual sources are isolated using track beam methods on array subapertures. The subaperture track beam spectra are then input as element data into an inversion approach that uses simulated annealing to estimate both environmental and source parameters. Environmental parameters include those associated with the seabed and source parameters include source depth, initial range, initial bearing, speed, and course. A key concept is that of space-time processing manifested in the cost function by coherent sums of product spectra over frequency, receiver pairs, and time sequence. Insight into the problem is obtained with simulated data by examining the coupling between individual parameters, including the coupling between source and environmental parameters. [Research supported by ONR.]
Johns Manville Acoustical Laboratory
Authors: Tinianov Brandon D. , Babineau Francis J.
Published: February 2014

Due to their long history in acoustics materials, the Johns Manville Corporation has maintained an acoustical laboratory in constant operation since the 1930s. The laboratory complex is accredited under NVLAP for a broad range of ASTM and ISO test methods. For classic architectural acoustics evaluation, the lab has a reverberant test suite with a 142-m3 source chamber and a 316-m3 receive chamber. The chambers’ common opening allows for 2.8 by 4.3-m samples and is qualified from 100–10000 Hz. Analysis of complex, three-dimensional systems conducted in a 176-m3 hemi-anechoic chamber qualified to 160 Hz. Both intensity and pressure measurements are possible via a 5 degree-of-freedom robotic positioning system. Research of open office acoustics and office furniture is performed in a 111- (to the grid, 142 total) m3 chamber designed to accept a suspended ceiling and vary its reverberation time from <0.3 to 2.3 s. In addition to these facilities, several benchtop and analytical resources are available.
Noise and structural dynamics test facilities at Boeing
Authors: Miller Wendell , Boston Donald , Pickrel Charlie
Published: February 2014

The noise and structural dynamics laboratories at Boeing provide a wide range of test and measurement services to the Boeing Company. Test data from these laboratories support all phases of the product life cycle across a diverse line of products and applications. The noise laboratory facilities include a low-speed free-jet acoustic wind tunnel, several anechoic and reverberation test chambers, a critical listening facility, and a materials test center. These facilities are supported with a network of data systems for in-lab testing and a variety of transportable data systems for field- and airplane-based testing. Structural dynamics laboratory facilities include large strongbacks and structural floors for component vibration testing, sonic fatigue test facilities, and vibration test facilities. These facilities are supported by a network of dedicated data systems for a wide range of modal, shock, vibration, and fatigue testing. Field tests are supported by a wide range of portable data systems and instrumentation trailers capable of large channel count measurements. This work will provide an overview of the test facilities and measurement capabilities of these laboratories.
The influence of flight speed on the ranging performance of bats using frequency modulated echolocation pulses
Authors: Boonman Arjan M. , Jones Gareth , Parsons Stuart
Published: February 2014

Many species of bat use ultrasonic frequency-modulated pulses to measure distance to objects. The flight speed of the bat will result in a compression of the echo, and in compression of the time of flight of the signal, both leading to distortion of the perceived range. By comparing Doppler errors incurred with the SCAT-filterbank model and cross-correlation, it was established that the effects of the echo compression are virtually independent of the two receiver models. A cross-correlation model was used to investigate Doppler tolerance of the ranging estimation and range-Doppler coupling separately. Range-Doppler coupling is considered a potential error for bats since a reference time (Tref) does not seem biologically feasible. Without using a reference time, range-Doppler coupling due to echo compression was found to vary between 10 and 30 ms in six bat species. With additional range-Doppler coupling due to the compression of the time of flight (34 ms at 2 m from the target), this leads to perceived target displacements between 4.5 and 6.6 cm at a flight speed of 6 m/s. Range-Doppler coupling can be reduced by linearizing the curvature and by increasing the ratio highest/lowest frequency of the pulse. The study further revealed how pulse duration, bandwidth and harmonics influence Doppler tolerance and range-Doppler coupling.
Application of the enhanced ray theory to benchmark problems
Authors: Maltsev Nick E.
Published: February 2014

Enhanced ray theory [Maltsev, J. Comp. Acoust. (in press)] was applied to benchmark problems. A new approach for searching of eigenrays, based on the structure of rays surface in phase space, was developed. The sound field is composed by numerous eigenrays, so the time and space structure of the field is preserved and available for interpretation.
The new Simrad EK60 scientific echo sounder system
Authors: Andersen Lars Nonboe
Published: February 2014

A widely used tool for fish abundance estimation and other marine research is the scientific echo sounder. Acoustic information obtained from scientific echo sounders such as target strength and target position can be valuable for describing individual targets whereas measurements of volume backscattering strength are suitable for describing a large number of targets distributed over a volume of water. The new Simrad EK60 scientific echo sounder system provides high-quality target strength, target position, and volume backscattering strength measurements over a large dynamic range for a wide range of frequencies (18–200 kHz). An overview of the EK60 will be presented and operation of the echo sounder will be demonstrated. The presentation will include demonstration of the calibration procedure of the EK60.
Experimental tests of a new method to monitor sea medium by analyzing ambient noise and reradiating it from a distant point
Authors: Alexander V. Furduev , Victor D. Svet
Published: February 2014

In-sea experiments show a possibility to estimate parameters of the water column by analyzing space-time characteristics of the natural ambient noise. If the noise is reradiated by sound transponder located at a distance from the receiver, a regenerative monitoring scheme can be implemented. In such scheme a feedback is present that increases the contrast of the spectrum maximums to higher accuracy. By increasing the amplification gain of the whole circuit (including the feedback loop of the underwater channel), one comes to a self-sustained oscillator, its frequency deviations are indicating variations of the medium parameters. Experimental examples are presented to confirm feasibility of the proposed monitoring technique for measuring temperature variations, current velocity, periods of internal waves, and other features of the water column. The method is especially applicable to small sea areas like straits, harbors, and lakes to monitor their environmental equilibrium or manifestations of human activity. [Work supported by RFBR, Project No. 00-05-64226.]
Cortical bone characterization by guided waves
Authors: Talmant Maryline , Bossy Emmanuel , Camus Estelle , Padilla Frederic , Laugier Pascal
Published: February 2014

The axial transmission method was first developed in 1958 to study the status of cortical bone during fracture healing. It has been subsequently used to investigate bone strength in osteoporosis. Two transducers are placed on the same side of the bone and the velocity of the first arriving signal on the receiver is measured. The present paper contributes to the understanding of the type of propagation involved in this technique when applied on bone. When using a propagation model for semi-infinite media the first signal is identified as the longitudinal lateral wave for a defined arrangement of transducers. However, the ratio of bone thickness over wavelength is of the order of unity and then normal modes of vibration give a non-negligible contribution to the reflected pressure. Whereas a lateral wave investigates the bone superficially, shell modes penetrate inside the material much more. Signal simulations, in vitro experiments and in vivo measurements using our prototype will be presented. Particular attention will be given to the influence of cortical thickness. The velocity of the first signal decreases with respect to the thickness, from the velocity of the lateral wave to the velocity of the extensional mode of the lowest order.
Modeling sound transmission through the pulmonary system and chest with application to diagnosis of a collapsed lung
Authors: Zhang Xiangling , Royston Thomas J. , Mansy Hussein A. , Sandler Richard H.
Published: February 2014

A study was undertaken to demonstrate the feasibility of using audible-frequency vibro-acoustic waves for diagnosis of pneumothorax, a collapsed lung. The hypothesis was that the acoustic response of the chest to external excitation would change with this condition. External acoustic energy was introduced into the trachea via an endotracheal tube. For the control (nonpneumothorax) state, it is hypothesized that sound waves primarily travel through the airways, couple to the lung parenchyma, and then are transmitted directly to the chest wall. In contradistinction, when a pneumothorax is present the intervening air presents an added barrier to efficient acoustic energy transfer. A theoretical model of sound transmission through the pulmonary system and chest region to the chest wall surface is developed to more clearly understand the mechanism of intensity loss when a pneumothorax is present, relative to a baseline case. The model predicts a decrease in acoustic transmission strength of as much as two ordersof magnitude when a pneumothorax is present. This is approximately in agreement with experimental measurements on mongrel cannies. Development of the model and its comparison with experimental canine studies will be reviewed. [Research supported by NIH NCRR Grant No. 14250 and NIH NHLBI Grant No. 61108.]
Forward-looking acoustic mine sensing
Authors: Costley R. Daniel , Sabatier James M. , Xiang Ning
Published: February 2014

A mine sensing system based on acoustic-to-seismic coupling sonifies the ground with high amplitude (120 dB), broadband (80–300 Hz) sound and measures the resulting ground vibration with a scanning laser Doppler vibrometer (LDV). Images produced by these scans show a distinct contrast in several frequency bands between ground vibrations over a buried mine and not over the mine. In order to reduce the risk to the vehicle and its operators and to allow a safe stopping distance for the vehicle, it is desirable that the system looks a significant distance in front of the vehicle. Experiments were conducted to investigate the feasibility of a forward-looking system. In a forward-looking system, both the sound source and the LDV are moved farther from the scanned area. This configuration both reduces the sound pressure level at the scanned area and decreases the angle at which the LDV beam strikes the ground. These effects reduce the contrast between the over-mine and off-mine signals. In addition, the image is distorted at the shallower LDV-ground angles. Results from these experiments will be presented and discussed. [Work supported by U.S. Army Communications-Electronics Command, Night Vision and Electronic Sensors Directorate.]
Simulation of particle motions in an acoustophoresis device
Authors: Brooks Todd L. , Apfel Robert E.
Published: February 2014

Particles in a liquid host can be continuously fractionated by combining a laminar flow with an ultrasonic standing wave oriented perpendicular to the flow direction. This kind of separation method can separate particles based on their relative compressibilities as well as on mass density and size. Experimental work has focused on separating particles ranging in size from 5 to 55 μm in resonant devices operating from 100 kHz to 1 MHz. A numerical simulation based on a hierarchical tree method has been developed to simulate particle motion in such a device. The flow field, primary acoustic forces, and secondary interparticle acoustic forces are all taken into account. Full three-dimensional simulations can be performed. This method may be useful in other application areas where large numbers of particles, drops, and/or bubbles are under the influence of acoustic forces. [Work supported by NASA through Grant No. NAG8-1351.]
Upward spread of Schroeder-phase maskers
Authors: Lentz Jennifer , Leek Marjorie , Dreisbach Laura
Published: February 2014

Harmonic complexes with phases selected according to the Schroeder algorithm can produce large differences in masking, depending on whether phases increase (positive Schroeder) or decrease (negative Schroeder) with frequency. This finding has been attributed to an interaction between the phase characteristics of auditory filters and the stimulus. The current study investigates effects of filter asymmetry on masking by harmonic complexes using an upward spread of masking paradigm. Maskers were Schroeder phase maskers with frequencies from 200 to 2000 Hz, and signal frequencies ranged from 1000 to 4000 Hz. When the signal fell within the masker bandwidth, it was added in-phase with the identical masker component. At signals below 2000 Hz, negative Schroeder maskers produced more masking than the positive maskers. When the signal frequency was above the masker, there was a rapid decrease in masking for both maskers, but for most subjects, the positive masker became more effective than the negative. This shift in the Schroeder masking effect may be related to phase changes occurring in the lower skirts of the auditory filters. [Work supported by NIH.]
Derivation of intensity-discrimination functions from loudness functions
Authors: Hellman William S. , Hellman Rhona P.
Published: February 2014

Intensity-discrimination functions are computed from their concomitant loudness functions in a procedure where the only adjustable parameter sets the scale to match the measured intensity-discrimination data. The equation connecting loudness to intensity discrimination is determined from monaural loudness- and intensity-discrimination measurements at 1 kHz. Predictions of intensity-discrimination functions are then computed for a low-frequency tone masked by an adjacent high-pass noise, for broadband noise, and for high-frequency tones at 12.5 and 16 kHz. Results show that the derived intensity-discrimination functions closely capture the overall shape of the experimental data. A U-shaped function is obtained for the partially masked low-frequency tone, whereas a function approximating Weber’s law is observed for broadband noise and also at 16 kHz. The good agreement between the calculated and measured functions implies that the form of the intensity-discrimination functions is strongly dependent on local variations in shape of the loudness functions. Together, these results provide further evidence to support the notion of an intimate relation between loudness and intensity discrimination. [Work supported in part by NEDO, Japan.]
Experimental validation of the state-switched absorber for two-component harmonic forcing
Authors: Holdhusen Mark , Cunefare Kenneth A. , Larson Gregg
Published: February 2014

A state-switched vibration absorber (SSA) is a semiactive device that is capable of instantaneously changing its dynamical state by altering its stiffness. However, the SSA can switch between more than one resonance frequency, providing a greater bandwidth as compared to classical tuned vibration absorbers. Modeling predictions indicate that with appropriate logic for switching between states, the SSA is more effective at vibration suppression than classical tuned vibration absorbers, when the system to be controlled is subject to a disturbance with more than one spectral component. This presentation considers the experimental validation of SSA performance for the suppression of vibration on a driven elastically mounted lumped mass system. The SSA considered here is implemented in a dynamical proof-of-concept demonstrator. State switching is effected through the use of a magneto-rheological fluid clamp to connect or disconnect a coil spring in parallel with another coil spring. The two coil springs, one switchable, the other not, constitute the spring element of an otherwise passive mass-spring-damper vibration absorber. The stiffness state is controlled by actuation of the MR clamp. The experimentally observed performance of the SSA will be presented and compared to modeling predictions. [This work is based upon work supported by, or in part by, the U.S. Army Research Laboratory and the U.S. Army Research Office under Grant No. 38955-EG, Dr. Gary Anderson, Technical Monitor.]
Wave vibration analysis and control of a transversely vibrating Timoshenko beam
Authors: Mei Carole
Published: February 2014

Apart from the modal description, vibrations in structures can also be described in terms of waves. In this paper, wave vibration analysis and control of a transversely vibrating Timoshenko beam are studied. The wave reflection and transmission characteristics under general discontinuity and general boundary conditions are presented. The reflection and transmission matrices for incident waves upon such discontinuities and boundaries are derived. Both free and forced responses of the Timoshenko beam are analyzed from wave reflection and transmission standpoint. The Timoshenko and the Euler–Bernoulli beam model are compared. Numerical examples of the free and forced vibrations of both slender and nonslender beams are presented to show the similarities and to signify the differences between the two beam models. Vibration suppression strategies from wave point of view are addressed.
Special properties of higher-order symmetric Lamb waves on plates
Authors: Werby Michael F. , Überall H.
Published: February 2014

Exact linear elastodynamic theory is used to derive expressions for all of the modes on a two-dimensional unloaded plate in an effort to understand certain features generated from the symmetric modes on plates and shells. In that context we explain the unusual nature of all S1 modes including the negative slope of the phase velocity with respect to wave number at critical frequency, the amplitude modulated nature of the transient solution in that frequency zone, and the fact that one type of elastic material has an infinite number of such unusual modes (materials with a Poisson ratio of exactly 1/3) while the remaining class only appears to have that property for the S1 mode. We review the asymptotic nature of all of the plate modes and show that the symmetric Lamb modes always have a plateau region in phase velocity relative to wave number and how many of the properties of the symmetric Lamb modes may be used for classification and detection of shells and plates.
Recursive Green function technique applied to acoustic wave propagation
Authors: Ferreira Mauro S. , Bauer Gerrit E. W. , Wapenaar Kees
Published: February 2014

Guided by similarities between electronic and classical waves, a numerical code based on a formalism proven to be very effective in condensed matter physics has been developed, aiming to describe the propagation of elastic waves in stratified media (e.g., seismic signals). This so-called recursive Green functions technique is frequently used to describe electronic conductance in mesoscopic systems. It follows a space discretization of the elastic wave equation in frequency domain, leading to a direct correspondence with electronic waves traveling across atomic lattice sites. An inverse Fourier transform simulates the measured acoustic response in time domain. The method is numerically stable and computationally efficient. Moreover, the main advantage of this technique is the possibility of accounting for lateral inhomogeneities in the acoustic potentials, thereby allowing the treatment of interface roughness between layers. Without those lateral variations, wave propagation across perfectly layered media with planar sources are equivalent to 1-D environments, and therefore should present localization effects. Inclusion of those variations breaks the symmetry and turns the wave propagation into a truly 2-D or 3-D problem, where localization is weaker or may not occur. Numerical techniques without lateral inhomogeneities may inadvertently overestimate localization effects.
Harry Levitt legacies: Studies of speech perception and intelligibility in children with cochlear implants
Authors: Tobey Emily A. , Geers Ann
Published: February 2014

Harry Levitt has contributed a substantial body of knowledge regarding the speech perception and production skills of hearing-impaired children. In this paper, Dr. Levitt will be honored by describing the speech perception, speech intelligibility, and acoustic characteristics of 136 cochlear implanted children between the ages of 8 and 9 who have at least 4 years experience with a Nucleus multichannel cochlear implant. Half of the children used auditory-oral modes of communication and the other half used total communication. The questions addressed are as follows. (a) Do children implanted before 5 years of age develop intelligible speech? (b) Are speech perception skills reflected in the acoustic measurements of speech in children with cochlear implants? (c) What factors are associated with intelligible speech in children with cochlear implants? The presentation will describe the population demographics, speech perception measures (including open and closed set speech perception performance), and measures of speech production (including speech intelligibility, communication breakdowns, parental rating scales, and acoustic characteristics). Factors contributing to high levels of speech perception and intelligibility will be described and contrasted. Implications for the development of intelligible speech will be discussed, particularly as it relates to mode of communication. [Work supported by NIH-NIDCD.]
Development of perceptual dimensions lags the ability to perceive details
Authors: Gray Lincoln , Breier Joshua , Diehl Randy , Haardt Peggy , Turley Christine
Published: February 2014

Studies with humans and animals show that the ability to discriminate fine changes along an auditory continuum develops before the ability to appreciate the continuum. The visual analogy would be seeing details before the ‘‘big picture.’’ This trend is discussed with data from normal newborn chickens responding to changes in frequency and azimuth, from patients after corrected congenital hearing loss, and from children and chickens exposed to lead. In each instance, subjects respond to small changes before they respond consistently to large changes. Multidimensional scaling can reveal the ‘‘attribute’’ or perceived dimension that distinguishes a set of stimuli. The attribute is compared to the difference limen. These data suggest that discriminations can emerge before the appropriate perception of a sensory attribute. Perceptual development may not always involve a process of increasingly fine discriminations along continua that are established at an early age, but instead may involve the ability to process global pattern. Some theories suggest that perceptions ‘‘sharpen’’ over development. Sharpening does not seem to occur in situations we have studied: over normal development, after early deprivation, or after early lead poisoning. If confirmed in other situations, this could suggest novel approaches to ameliorate some early perceptual processing deficits.
3-D compound imaging with refraction and motion correction
Authors: Carson Paul L. , Kruecker Jochen F. , LeCarpentier Gerald L. , Meyer Charles R. , Fowlkes J. Brian
Published: February 2014

The early goal of multiview imaging was delineation of quasi-specular image boundaries. Medical compound imaging was partially replaced because of resolution loss by refraction, misregistration, and tissue motion, and completely replaced due to incompatibility with real-time imaging. Three potential improvements in: boundary delineation, volumetric contrast-to-noise ratio, and Doppler anisotropy reduction (BC&D) have remained an attraction of compounding. Now marketed, in-plane compounding in real-time and in extended field of view imaging offer the potential for in-plane, image-based reregistration of multiple views. Image volume-based registration (IVBaR) of separate angular views in 3-D data sets allows full 3-D displacement corrections. Compounding out of the image plane (elevational compounding) increases the number of independent views, increasing potential yield from improvements BC&D. Our work has been in elevational compounding with conventional linear arrays, in contact with, and partially moving the proximal tissues. IVBaR using the mutual information metric and thin plate spline interpolation of warped volumes has produced exceptional reclamation of spatial resolution along with the expected improvements BC&D. Full-volume, warped registration, and a faster, subvolume registration have been compared in vivo and with realistic beam aberrations in test objects. [Work supported in part by PHS Grant No. R01HL54201 from the NHLBI.]
Ultrasound image based on ultrasound characterization of tissue microstructure of spontaneous rat mammary tumors
Authors: Oelze Michael L. , O’Brien William D. , Zachary James F.
Published: February 2014

Experimental results of acoustic backscatter from spontaneous mammary tumors in rats are obtained over the frequency range of 1 to 15 MHz. The power spectrums (dB) from the experimental results are compared to theory in order to obtain information about tissue microstructure. The theoretical power spectrum assumes an isotropic 3-D Gaussian function as the spatial autocorrelation function used to describe the distribution of scatterers in the tissues. The theoretical power spectrum can be shown for small scatterers (diameter less than 0.2 mm) to be proportional to the Rayleigh spectrum times a second-degree polynomial in frequency. Independent values of the average scatterer diameter and scatterer concentration are obtained from the coefficients of the second-degree polynomial. Scatterer sizes and concentrations measured by ultrasound backscatter are compared to histological data. B-mode images are made of the tumors and surrounding tissues with superimposed regions-of-interest (ROIs) parameterized by the scatterer sizes and concentrations. [Work supported by NIH CA 079179.]
Response on the surface of a viscoelastic medium due to subsurface acoustic sources with application to vascular medical diagnosis
Authors: Yazicioglu Yigit , Royston Thomas J. , Loth Francis
Published: February 2014

The vibratory response at the surface of a viscoelastic material due to buried spherical and cylindrical acoustic sources is considered theoretically, numerically, and experimentally. An analytical solution that accounts for the compression, shear, and surface wave response to the buried source in a halfspace is formulated and compared with numerical finite-element simulations and experimental studies on finite-dimension phantom models. The focus here is on developing a better understanding of how biological soft tissue affects the transmission of vibro-acoustic energy from biological acoustic sources below the skin surface, such as a turbulent regime in an artery caused by a partial blockage. Such an understanding could catalyze the development of noninvasive procedures using an array of inexpensive acoustic sensors on the skin surface for the identification and monitoring of vascular blockages, a precursor to many serious cardiovascular diseases. [Research supported by NIH NCRR Grant No. 14250.]
Development of a model for acoustic liquid manipulation created by a phased array
Authors: Faidley LeAnn E. , Mann J. Adin
Published: February 2014

Acoustic Liquid Manipulation (ALM) is the application of the nonlinear effects of high-powered ultrasound to move buoyant objects, create fluid flow, or manipulate fluid–fluid interfaces. Work being done at NASA Glen Research Center indicates that this technique has the possibility to be used to control the location of air bubbles in space vehicle fuel tanks, keeping them away from outlet lines. In order to determine whether ALM is feasible for this and many other possible applications, a model that predicts the nonlinear behavior of sound created by a variety of source configurations needs to be developed. This was the goal of this project. In this paper the development of a model for radiation pressure, acoustic streaming, and acoustic heating due to a phased array configuration will be outlined. The results of the model will be discussed, and a comparison will be made with experimental data.