bluuebunny/crossref_metadata_2025 huggingface dataset:
Shelf-break tidally induced environmental influences on acoustic propagation
Authors: Oba Roger , Finette Steven , Shen Colin , Evans Thomas
Published: October 2013

Continuous wave propagation in the 100–500 Hz band in littoral regions depends upon both time-dependent oceanography and bathymetry. The environmental influences interact nonlinearly in the acoustical time variation, especially since the diurnal tide surface height changes creates time-dependent total water depth. A submesoscale hydrodynamic model developed by Shen and Evans is used with tidal forcing and a simple shelf-break bathymetry to produce surface height variation and internal wave activity due to internal tide in a stratified ocean environment. A three-dimensional parabolic equation acoustic model is used to acoustically probe this environment at various bearings relative to the shelf break and the resulting internal tidal dynamics. In particular, the acoustical results are examined for three-dimensional effects such as horizontal refraction. First, the influence of bathymetry alone is shown, and then compared to the full environment due to hydrodynamic action. The relative influences will then be compared by various measures such as modal decomposition, acoustic energy summed over depth, and signal gain degradation. [This research is sponsored by the ONR.]
Pressure and temperature fields from high-intensity focused ultrasound: Modeling the impact of bubbles and cavitation
Authors: Wu Tianming , Roy Ronald. A , Holt R. Glynn
Published: October 2013

The propagation of high-intensity focused ultrasound (HIFU) in tissue-mimicking phantoms is modeled via a finite difference time-domain simulation. Above a threshold pressure, cavitation activity results and the HIFU focal zone becomes a bubbly medium. We assume an effective medium and account for the impact of bubbles by computing modified effective sound-speed and attenuation coefficients, where the latter includes cavitation-related dissipation mechanisms. Stability criteria establish the bubble equilibrium sizes, and comparison with experiments provides an estimate of the bubble number density. Nonlinear bubble responses are computed numerically and the resulting cycle-averaged void fraction is used to estimate the effective sound speed using a Woods approximation. Computed absorption cross sections related to viscous dissipation and the absorption of reradiated sound yield the effective attenuation coefficient. Using the updated sound-speed and attenuation coefficients, the pressure field is recomputed in an iterative process. Heat deposition is estimated using the averaged acoustic intensity as the heat source along with the evolving attenuation coefficient. The space-time-dependent temperature field and thermal dose is then calculated. Results indicate enhanced heating rates as well as a tadpole-shaped lesion that grows towards the HIFU transducer. [Work supported by the US Army.]
Observations of cavitation activity and lesion growth in optically clear tissue phantoms
Authors: Thomas Charles R. , Farny Caleb H. , Roy Ronald A. , Holt R. Glynn
Published: October 2013

Above a certain acoustic pressure threshold the heating rate of a tissue-mimicking phantom (as well as in vivo tissue) by high-intensity focused ultrasound (HIFU) is greatly enhanced. This enhanced heating regime has been shown to correlate well with an increase in cavitation activity; thus, it is believed that the enhanced heating is the result of bubbles formed at the focus of the HIFU source. In this talk we report the results of work carried out to observe the cavitation activity in the focus of a 1.1-MHz source, using optically clear acrylamide/BSA tissue phantoms. Three different methods were employed to make the measurements: simultaneous passive cavitation detection (PCD) and video imaging, simultaneous PCD and light emission measurements (using a photomultiplier tube), and video imaging with back light. Results complement previous work by other groups which showed that thermal lesion growth progresses towards the HIFU source; however in contrast to those studies, our results indicate that at some level cavitation is always present during the formation of thermal lesions in these particular tissue phantoms. [Work supported by the US Army and the Center for Subsurface Sensing and Imaging Systems via NSF ERC Award Number EEC-9986821.]
High-speed photography and acoustic emission synchronized observation of ultrasound induced acoustic cloud cavitation
Authors: Ikeda Teiichiro , Tosaki Masataka , Yoshizawa Shin , Matsumoto Yoichiro
Published: October 2013

Though the violent collapse of the acoustic cavitation during ultrasound therapy may cause tissue traumas, it has a potential for therapeutic benefits if it is carefully controlled. The investigation of a two-frequency focused ultrasound method for the acoustic cloud cavitation control for lithotripsy is discussed. In the forcing cycle, cavitation is controlled by generation, growth, and shape stabilization during a high-frequency (1–4 MHz) phase, and a violent forced collapse that produces very high pressure during a low-frequency phase (400–550 kHz). Ultra high-speed photography for various conditions, gas concentration in the media and the acoustic field properties, are conducted. The photography (up to 200 MHz) framing rate is synchronized with the measurement of the acoustic emission from the cavitation bubbles by a concave PVDF hydrophone with a high directivity and a broadband response up to 10 MHz. The behavior of the cloud cavitation during the two-frequency cavitation control cycle is investigated with respect to the acoustic emission of the cavitation bubbles. The shape stabilization of the cloud cavitation and the high-pressure concentration on the solid surface by the forced collapse of the bubble cloud are discussed.
Controlling a high intensity focused ultrasound induced cavitation field via duty cycle
Authors: Farny Caleb H. , Thomas Charles R. , Holt R. G. , Roy Ronald A.
Published: October 2013

Cavitation has been implicated in the lack of control over the shape of thermal lesions generated by high-intensity focused ultrasound (HIFU). A coincident effect the decline in the acoustic emissions from cavitation at the focus suggests that the HIFU energy is shielded from the focal region, possibly by prefocal bubble activity. Most clinical techniques employ continuous-wave (CW) ultrasound, which can exacerbate the problem depending on the acoustic intensities employed. This talk presents a series of experiments investigating techniques to control HIFU energy delivered to, and cavitation activity within, a tissue phantom. A passive cavitation detector (PCD) is employed as a sensor of cavitation activity. For 1.1-MHz CW ultrasound at focal pressures above 3 MPa, bubble shielding was inferred from a steady decline in the PCD signal over time. By lowering the duty cycle the PCD output remained constant over time. Finally, driving the HIFU source initially with a CW signal and then switching to a pulsed signal resulted in shielding, recovery, and a stable PCD signal, thus demonstrating our ability to control cavitation activity during HIFU exposure. [Work supported by the U.S. Army and the Center for Subsurface Sensing and Imaging Systems via NSF ERC Award No. EEC-9986821.]
A model for image formation in vibro-acoustography
Authors: Silva Glauber T. , Fatemi Mostafa
Published: October 2013

Vibro-acoustography is a technique that images the vibro-acoustic response of an object to the harmonic ultrasound radiation force. The system point-spread function is associated to the radiation force exerted on a point-target by a dual-frequency ultrasound beam. So far the radiation force was calculated by assuming a dual-frequency beam composed by two plane waves. This reduces the radiation force to a one-dimensional quantity neglecting transverse components. Here, we model the radiation force as a three-dimensional vector. In this model, the scattering of a dual-frequency beam with any spatial distribution by a point-target is solved. The incident and scattered fields are used to calculate the radiation force on a sphere whose radius approaches to zero. The force is proportional to the gradient of the product of the incident wave amplitudes. Evaluation of the radiation force produced by a two-element co-focused transducer shows that the transverse component of the force is about −20 dB smaller than the corresponding axial component. Effects of the transverse force on image formation are still under investigation. In conclusion, the presented model describes vibro-acoustography systems with dual-frequency beams of any spatial distribution. [Work partially supported by Grant No. DCR2003.013-FAPEAL/CNPq.]
Vibro-acoustography for targeting kidney stones during lithotripsy
Authors: Owen Neil R. , Bailey Michael R. , Maxwell Adam , MacConaghy Brian , Khokhlova Tatiana D. , Crum Lawrence A.
Published: October 2013

Vibro-acoustography can be used to measure material properties and detect calcifications within the body. Two transducers (diameter 10 cm, curvature 20 cm, frequency 1.1 MHz) are placed with overlapping foci in degassed water and driven at different frequencies to produce a dynamic radiation force in the range of 5–50 kHz. A LabVIEW program instructs the transducers to sweep through this frequency range at 500-Hz increments while a synthetic cylindrical kidney stone is held in the focus in one of three ways: with a rubber band, within an acrylamide gel, or within a finger cot. A low-frequency hydrophone, 10 cm from the focus and 90 deg from the direction of propagation, detects the radiated acoustic emission from the stone. The average amplitude of five signals is recorded to measure the frequency response of the stone. Unbroken stones exhibited higher amplitude response at frequencies near 10, 25, and 35 kHz. Stones are moved to simulate patient breathing and different in-focus and out-of-focus acoustic emissions indicate that vibro-acoustography may potentially target kidney stones during lithotripsy. Comminution is improved in vitro by gating SWs with targeting. [Work supported by NIH Grants DK43881 and DK55674, NSBRI Grant SMS00203, and CRDF.]
Potential mechanism for the effect of shock wave rate in shock wave lithotripsy
Authors: Pishchalnikov Yuri A. , VonDerHaar Richard J. , McAteer James A. , Pishchalnikova Irina V. , Bailey Michael R. , Williams James C. , Evan Andrew P.
Published: October 2013

Artificial stones break significantly better when shock waves (SWs) are delivered at 0.5 Hz than at 2 Hz, and patients treated at slower rates have improved stone-free rates. One possible explanation may be cavitation bubbles that might persist between SWs at high rate and distort subsequent SWs sufficiently to reduce their effectiveness at stone comminution. High-speed photography gives evidence that bubble numbers are greater at higher rates. B-mode ultrasound echo in the free field typically disappears between pulses administered at 0.5 Hz but persists at 2 Hz. Fiberoptic hydrophone measurements at 2 Hz showed, in the free field of an electrohydraulic lithotripter, that SW negative tail was truncated, and proximal to a stone, that SW waveform varied and was distorted such that often the positive pressure amplitude was reduced. Changes in waveform proximal to stone declined as the stone disintegrated and fell away. Thus, data support the persistence of cavitation bubbles at high SW rate, and consequent distortion of waveform. Additionally, debris from a stone appears to accentuate this effect. These measurements may help not only define an effective SW rate and shape, but may further improve our understanding of the comminution process. [Work Supported by NIH-DK43881, DK55674, and ONRIFO-N00014-04-1-4010.]
Diagnostics and reduction of propulsion airframe aeroacoustic interactions
Authors: Mengle Vinod G. , Stoker Robert W. , Elkoby Ronen
Published: October 2013

In the past, significant reduction in aircraft noise has been achieved by studying engine noise and airframe noise in isolation as two separate components. However, when an engine is installed on an aircraft the flow and acoustic interactions between them produce a total noise signature which is often different than the sum of the component noise signatures. While take-off conditions are typically dominated by engine noise, approach conditions are characterized by both engine and airframe noise. Nevertheless, propulsion airframe aeroacoustic (PAA) interactions are present under all conditions and gain in importance when engine or airframe noise is further reduced. This paper focuses on the diagnostics and reduction of the flow-acoustic interaction effects between an engine exhaust and the airframe, especially the high-lift system on wings. Flow and acoustic results are presented for an isolated scale-model nozzle in a free jet, and also when it is installed under a wing at take-off and approach conditions. The difference between these two noise signatures, in the far field and at the source, captures the PAA effect. In particular, the PAA effect due to changes in nozzles, pylons, and flaperons is presented and the overall noise reducing mechanisms are postulated.
Further developments in aircraft flyover noise synthesis and propagation
Authors: Sullivan Brenda M. , Rizzi Stephen A.
Published: October 2013

Subjective assessments of the noise from aircraft flight operations require time histories of acoustic pressure at listener positions. Synthesized sound has an advantage over recordings by allowing the examination of proposed aircraft, flight procedures, and other conditions or configurations for which recordings are unavailable. A two-stage process for synthesizing flyover noise at listener positions on the ground was previously developed, enabling the creation of an immersive test environment. The first stage entails synthesizing time histories at the flying source. Rizzi and Sullivan [J. Acoust. Soc. Am. 113, 2245 (2003); 114, 23 (2003)] presented an approach for synthesizing sound from broadband sources (e.g., jet noise) based on predicted 1/3-octave band source spectra, with the inclusion of temporal fluctuations based on empirical data. Reported here are further developments in the synthesis of tone-dominated source (e.g., fan noise). The second stage entails propagation of the synthesized sound from the flying source to the listener. Improvements in the atmospheric attenuation part of the second stage are also presented.
Application of the Green’s function parabolic equation (GFPE) method to realistic outdoor sound propagation scenarios
Authors: Cooper Jennifer L.
Published: October 2013

The Green’s function parabolic equation (GFPE) is a powerful method for outdoor sound propagation prediction. Given appropriate inputs, GFPE predictions can include the effects of terrain, ground cover, sound speed profile, and turbulence on atmospheric propagation. In many situations, however, access to such input information can be limited. The input data resolution and accuracy can have a significant impact on model output accuracy. In turn, variability of terrain and sound speed profile and statistical aspects of the turbulence impact the model parameter requirements. For example, in the presence of turbulence, lower limits on computational grid height are determined by turbulence correlation scales as well as acoustic wavelength. Input data resolution requirements and some techniques that may be employed to account for insufficient input data will be discussed. Model results for realistic situations will be presented.
Forest effects on acoustic pulse propagation
Authors: Albert Donald G. , Perron Frank E. , Decato Stephen N.
Published: October 2013

A series of short-range outdoor measurements was conducted to investigate forest effects on acoustic pulse propagation. The measurements investigated seven different forest stands with a variety of different tree species including deciduous, evergreen, and mixed. A 0.45-caliber blank pistol shot was used as the source of the acoustic pulses, and the signatures were recorded 30 to 60 m away using a digital seismograph. An identical measurement was conducted in an open field for comparison. The recorded waveforms generally show the elongation characteristic of pulse propagation over a highly porous ground surface, with high-frequency reverberation arrivals superimposed on the basic waveform shape. These measurements can provide parameters useful for theoretical predictions of acoustic propagation within forests, and also illustrate some of the natural variability encountered in these environments. [Work funded by U.S. Army.]
Three generic signal processing techniques in fluctuation-based processing for increasing gain
Authors: Wagstaff Ronald A. , Gilbert Kenneth E.
Published: October 2013

Fluctation-based processors (FBPs) utilize an approach to signal processing that recognizes there is signal present or signal absent information imbedded in the fluctuations of the spectral time-histories. FBP algorithms are designed to focus on the changes in the fluctuations that are caused by a signal being present. There are three generic classes of FBP. Each class is defined by the fluctuating parameter and the method that the signal processing algorithm uses to exploit it. Typical gains include increases in signal-to-noise ratio, spectral and spatial resolution, and auto-identification of signals. The signal processing versatility of two of the classes provide additional gains by increasing temporal coherence. This versatility also led to development of processors that self-adapt to become more robust and provide higher gains. This includes adaptive processors that utilize the fluctuations to self-tune their governing equations. Thus they are able to preserve desired signals, while eliminating noise, transients, and undesirable signals, e.g., clutter. The operational manner of these three classes of FBP will be described. Key equations and algorithms will be explained. Results from single sensors and arrays for undersea and atmosphere acoustic data will be presented. [Work sponsored by the U.S. Army under Contract No. DASG60-00-C-0061.]
A multiscale computational approach for structural and acoustic medium-frequency vibrations
Authors: Riou Herve , Ladeveze Pierre
Published: October 2013

Today, all major numerical modeling techniques for the analysis of medium-frequency vibrations are based on finite element or boundary element approaches. In order to account for small-wavelength phenomena, these techniques require huge numbers of degrees of freedom. High-frequency approaches, such as statistical energy analysis or any of its improved variations, do not appear to be suitable for medium-frequency vibrations: the resulting vibrational behavior is too smooth and, in general, the coupling loss factor cannot be calculated in a predictive way. The variational theory of complex rays (VTCR) is a predictive computational tool for dealing with medium-frequency vibration problems. This strategy is based on a multiscale treatment of the shape functions (propagative and evanescent waves) chosen to represent the solution. All the waves are taken into account and only the amplitudes of the waves (the slowly varying scale of the solution) are discretized. The boundary and interface conditions between substructures are weakly enforced using an ad hoc variational formulation. The performance of the VTCR for an acoustic problem will be assessed.
Reducing the dispersion error in acoustic wave modeling with modified integration rules
Authors: Yue Bin , Guddati Murthy N.
Published: October 2013

Numerical analysis of transient acoustic wave propagation is often performed using finite element or finite difference methods along with central difference time stepping. Such analysis results in wave velocities that are different from exact ones. For conventional algorithms, this dispersion error is second order with respect to discretization parameters. In this paper, modified integration rules are combined with a modified central difference scheme to reduce this error to fourth order. Essentially, the locations of integration points used for evaluating the system matrices are selected such that the wave velocity error is minimized. It was found that the optimal integration points are square roots of 2/3 for the stiffness matrix, which eliminates the anisotropy in the second-order error. The optimal integration points for mass matrix, which depend on the wave velocity, the mesh size, and the time-step size, are also identified to completely eliminate the second-order error. The resulting dispersion error is thus reduced to fourth order. Numerical experiments illustrate that the proposed method has superior performance over existing methods, not only for structured square meshes, but also for unstructured meshes.
Acoustic radiation by a submerged source in shallow water—Influence of the boundaries
Authors: Charmes Emmanuel , Beaujean Pierre-Philippe , Cuschieri Joseph M.
Published: October 2013

The acoustic radiation and scattering characteristics of an acoustic source in an unbounded deep water environment are different from those in a shallow water environment, where one has to take into account the influence of the boundaries on the source radiation impedance. In this paper the influence of the waveguide (surface and bottom of the ocean in a shallow water environment) on the radiation from an elastic noise source is investigated by means of a superposition method. The radiated sound is initially determined from the scattering of an incident wave from the elastic target. Using the superposition method [A. Sarkissian, J. Acoust. Soc. Am. (1994)], the scattered field, including multiple scattering effects, is computed and represented by a series of point sources positioned inside the scatterer. A number of calibration points located at the surface of the scatterer are selected to determine the source strength of each point source using a least square approximation. Having obtained the source strength of each point source, the combined propagation field in the waveguide from all point sources and the influence back on the source are determined using normal mode or ray tracing solutions common in underwater sound propagation. [Work supported by ONR.]
Characterizing close fitting enclosures for fluid-loaded cylindrical sources
Authors: Cuschieri Joseph M.
Published: October 2013

The influence of a close fitting enclosure on the radiated noise from a submerged (in water) acoustic source has been shown to be beyond the scope of simple close fitting enclosure expressions found in some textbooks, especially when dealing with relatively soft intermediate layers [Cuschieri, J . Acoust. Soc. Am. 115, 2537 (2004)]. A more detailed analysis is thus warranted. Using a multilayer shell approach, with the innermost layer representing the source with uniform radial velocity, the middle layer representing the intermediate isolation layer and the outside layer representing the exterior cladding, with water fluid-loading on the outside of the exterior cladding, the insertion loss (IL) of the multiple layers is investigated for different intermediate layer materials, different exterior cladding layer characteristics and source size. IL results are presented as a function of frequency and layer/cladding characteristics. From the formulation the behavior of the intermediate layers is also obtained which help explain the IL results. [Work sponsored by ONR.]
Effects of a prosodic control approach for patients with motor speech disorders
Authors: Kobayashi Noriko , Hirose Hajime , Koike Minako , Hara Yuki , Mori Hiroki , Kasuya Hideki
Published: October 2013

For patients with motor speech disorders, the Lee Silverman method (Ramig, 1997) has been known as an effective voice therapy method. In our clinical experiences, however, some Japanese patients could not easily produce very loud voice required in the method, presumably due to the cultural background. Therefore, in this study, a prosodic control approach called ‘‘the intonation emphasis therapy’’ was used as well as the Lee Silverman method for three types of patients. The disorder types were amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PK), and olivo-ponto-cerebellar atrophy (OPCA). Acoustic analyses revealed wider F0 ranges after the intonation emphasis therapy than the Lee Silverman method for three types of the patients. In the perceptual judgments by speech therapists regarding articulation, voice quality, intonation, and abnormal impression of speech, better ratings were obtained for the intonation emphasis therapy than for the pretherapy speech and the Lee Silverman method in the patients with ALS and PK. However, the listeners perceived inappropriate intonation and increased abnormality for the OPCA patient after the intonation emphasis therapy. It was suggested that our therapy method was effective for patients with motor speech disorders unless the disorders were associated with poor muscular coordination such as OPCA.
Vowels and final consonant production by adults with Down’s syndrome
Authors: Fung Mary , Decopain Rizzah , McGarr Nancy
Published: October 2013

Speech production studies have suggested a typical voice quality as well as vowel and consonant errors in speakers with Down’s syndrome. In this study, the production of bVt or bVd words produced by ten adults with Down’s syndrome and age and gender matched controls was examined for influence of final consonant voicing status. Acoustic measures of vowel duration and consonant voicing were made. Listener judgments were also obtained. Contrasts between vowels pairs were maintained by most subjects, e.g., duration for tense vowels was greater than for lax, although duration for the test subjects productions was greater overall than for the controls. Similarly, consonant voicing contrasts were maintained, e.g., vowel duration preceding voiced consonants was longer than for voiceless, but again overall duration was longer for the Down’s syndrome adults than the controls. The results of the acoustic analyses suggest that while the test subjects demonstrate knowledge for producing final voicing contrasts, aspects of fine coordination are not achieved. Intelligibility of final consonants was high and listener judgments generally agreed with acoustic measures. [Work supported by McNair Scholars’ Program to St. Johns University.]
Speech perception in noise among language-impaired individuals
Authors: Wayland Ratree , Lombardino Linda
Published: October 2013

This study compared and contrasted the ability to process speech signals between language-impaired individuals and their age-matched normal controls. Participants were administered a speech categorization task and a sentence processing task. A synthetic /ba–da/ continuum varying in second formant onset frequencies was used in the speech categorization task and 64 short (4–5-word-long) English sentences were used in the sentence processing task. The stimuli were presented with and without background noise to participants for categorization and identification. The /ba–da/ categorical boundaries and the number of target words correctly identified by two groups of participants under the two presentation conditions were compared. A connection between phonological processing and language impairment was discussed.
Cortical networks underlying audio-visual speech perception in normal-hearing and hearing impaired individuals
Authors: Yoo Julie J. , Guenther Frank H. , Perkell Joseph S.
Published: October 2013

Functional magnetic resonance imaging (fMRI) was used to investigate the brain activity underlying audio-visual speech perception in normal-hearing and congenitally deaf individuals. Data were collected while subjects experienced three different types of speech stimuli: audio stimuli without visual input, video of a speaking face without audio input, and video of a speaking face with audio input. A control condition consisted of viewing a blank screen. The stimuli were vowels or CVCV syllables, presented in different blocks. Active brain regions for normal-hearing subjects during the visual-only condition included visual cortex, angular gyrus, fusiform gyrus, and auditory cortex, as well as premotor areas in the frontal cortex. The pattern of activation found for deaf subjects while viewing visual-only stimuli was similar to that of normal hearing subjects, but showed distinctly more activity in the right hemisphere (for both vowels and CVCVs), and far less activity in premotor and parietal cortex. Interestingly, the pattern of activity for deaf subjects in the visual-only case was found to be similar to normal-hearing subject activation in the audio-visual case. Finally, effective connectivity analyses were done to investigate connectivity between brain regions in the different conditions for both groups of subjects. [Research supported by NIDCD.]
Acoustic scattering by axisymmetric finite-length bodies
Authors: Reeder D. Benjamin , Stanton Timothy K.
Published: October 2013

A general scattering formulation is presented for predicting the far-field scattered pressure from irregular, axisymmetric, finite-length bodies for three boundary conditions—soft, rigid, and fluid. The formulation is an extension of a two-dimensional conformal mapping approach [D. T. DiPerna and T. K. Stanton, J. Acoust. Soc. Am. 96, 3064–3079 (1994)] to scattering by three-dimensional finite-length bodies. This extended formulation, which is inherently numerically efficient to evaluate, involves conformally mapping the surface of an irregular, finite-length body to a new, orthogonal coordinate system in which the separation of variables method may be used to solve the Helmholtz equation and satisfy the boundary conditions. Extensive comparisons with previously published results using other formulations are presented. This formulation is shown to be very accurate in the prediction of scattering from smooth, symmetric bodies for a wide range of frequencies (Rayleigh through geometric scattering region), scattering angles (monostatic and bistatic), aspect ratios, and for each of the three boundary conditions listed above. Reasonable agreement has also been demonstrated for irregular, realistic shapes with soft boundary conditions. [Work supported by ONR.]
Conquering space and time—for art’s sake
Authors: Case Alex U.
Published: October 2013

While sound within a performance space must adhere to the laws of physics governing its propagation, the music synthesized for loudspeaker playback may take some liberties. Recording artists—with the help of the signal processing tools available in the recording studio—often fabricate multiple, physically unrealizable, audio spaces for simultaneous presentation in a single music performance. Additionally, these musicians are free to slow, accelerate, repeat, and reverse time for musical benefit. This paper isolates and demonstrates some of the unusual space- and time-focused synthesis techniques in popular recorded music, evaluating their technical basis and artistic merit.
The modulation rate transfer function of a Rissos dolphin, Grampus griseus, using the envelope following response.
Authors: Mooney T. Aran , Nachtigall Paul E. , Yuen Michelle M.
Published: October 2013

Auditory evoked potentials (AEPs) were used to obtain a modulation rate transfer function (MRTF) of a young, stranded Rissos dolphin (Grampus griseus). The animal’s neurological response to sound was stimulated by triangle-shaped broadband clicks, 1/2 ms in duration, played at presentation rates from 100 to 2000 Hz. These stimuli were played from a transducer 1 m in front of the subject, within a calibrated rehabilitation pool. The AEP responses were recorded using human EEG sensors attached by two soft suction-cups, placed just behind the blowhole and in front of the dorsal fin, respectively. By playing the stimuli at different rates, from low to high frequency, it was possible to determine the maximum and most efficient modulation rate, to be used in an AEP audiogram. The MRTF was similar to other cetaceans as it is low-pass in shape. Corner frequencies were somewhat lower than other published marine mammal MRTFs, dropping steeply after 1000 Hz. At this frequency, the evoked potential was highest, 230 nV, compared to noise levels in the tens of nV. Thus, 1000 Hz was determined to be the modulation rate used in determining the animals AEP audiogram.
Fluctuations of high-frequency sound field in shallow water in the presence of internal waves
Authors: Badiey Mohsen , Katsnelson Boris , Pereselkov Serguey
Published: October 2013

The structure of space-time fluctuations of a high-frequency (several kHz) sound field in a shallow water waveguide is considered. The sound field fluctuations due to internal and surface waves show different temporal variability. The perturbation theory within the framework of ray description is applied in order to derive some analytical estimation of fluctuations of arrival time and vertical angle distribution of high frequency broadband acoustics signals. The parabolic equation is used for numerical modeling of space-time fluctuations and vertical sound field intensity distribution. The experimental measurements of ocean dynamics from recent acoustic experiments are used as input data in numerical simulation of sound field fluctuations. [Work was supported by ONR and CRDF].
The relative effects of sound-speed variability in the water column versus the seabed on normal-mode propagation in shallow water
Authors: Frisk George V. , Sellers Cynthia J. , Souza Luiz L.
Published: October 2013

Normal-mode propagation in shallow water is influenced by variations in the acoustic properties of both the water column and the seabed. Specifically, the sound speed in the water may fluctuate due to the passage of an internal wave, while the sound speed in the bottom may change due to variable geological features. Assessing the relative effects of the water column versus the seabed on the characteristics of modal propagation is critical to the understanding of both the forward and inverse problems in shallow-water acoustics. In this paper, perturbation theory is combined with a Pekeris waveguide model to provide an analytic formalism for evaluating the delicate interplay between the water column and the seabed in shallow water propagation. In particular, the relative contributions of sound-speed fluctuations in the water and the bottom to variations in the modal eigenvalues are determined. The results are affected by both the strengths of the fluctuations and the magnitudes of the background modal eigenfunctions in the water and the seabed. The complexity of the problem is illustrated with synthetic and experimental data. [Work supported by ONR.]
A metric for evaluating speech intelligibility and quality in hearing aids
Authors: Kates James M. , Arehart Kathryn H.
Published: October 2013

Noise and distortion reduce speech intelligibility and quality in hearing aids, but there are no metrics that encompass both noise and distortion. This presentation introduces new intelligibility and sound-quality calculation procedures based on the Speech Intelligibility Index [ANSI S3.5-1997]. The SII involves measuring the signal-to-noise ratio (SNR) in separate frequency bands, modifying the estimated noise levels to include auditory masking, and computing a weighted sum across frequency of the modified SNR values. In the new procedure, the estimated SNR is replaced by a signal-to-distortion ratio (SDR) computed from the coherence between the input and output signals of the system under test. The SDR replaces the system noise estimate with the combined noise and nonlinear distortion. For the procedure, the signal is divided into three regions comprising the low-, mid-, and high-level signal segments. The SII is then calculated for each region using the corresponding coherence. The three coherence SII values are then combined to predict the intelligibility and the sound quality for the device under test. The coherence SII procedure is shown to be accurate for both normal-hearing and hearing-impaired listeners for additive noise, peak-clipping distortion, and center-clipping distortion. [Work supported by GN ReSound (JMK) and the Whitaker Foundation (KHA).]
Hearing aids: real world outcomes of the engineering feats
Authors: Bentler Ruth
Published: October 2013

It is often the case that software and hardware designs result in profound changes in the way hearing aids function. However, designing engineers must rely on feedback from others’ disciplines as to how these devices are evaluated and used in the ‘‘real world.’’ Directional microphone systems, noise reduction algorithms, and feedback cancellation schemes are all designed to eliminate unwanted interference. How those functions work in the real world, either independently or concurrently, will be explored.
Systems analysis of advanced quiet aircraft
Authors: Olson Erik , Hill Geoffrey , Brown Sherilyn , Geiselhart Karl , Burg Cecile
Published: October 2013

To achieve future goals for the reduction of aircraft community noise, it may be necessary to use unconventional engine and wing arrangements. Prediction of the resulting noise benefits cannot be made without taking into account the effect of the configuration on the whole aircraft system, including the impact on the aerodynamics, weights, and systems integration. Systems studies have been conducted that quantify the impact of various configurations on both the performance and noise of the aircraft. In this paper, the results for several systems studies are presented. In one study, a large matrix was assembled for candidate configuration options for a blended wing–body (BWB) aircraft–including engine, inlet, and nozzle types and placement options—and ranked based on prioritization between noise benefits and performance penalties. In another study, a pair of concepts was developed and evaluated with the goal of simultaneously reducing the noise produced and reducing or eliminating the production of harmful chemical emissions. Finally, a BWB configuration was studied to determine the sensitivity of the overall noise to the levels of the various engine and airframe sources, quantify the airframe shielding benefits using experimental data, and explore the effects of wing trailing-edge extensions on the shielding.
Acoustically assisted cleaning in microelectronics below 65 nanometers (nm): An urgent need to understand mechanisms and effects
Authors: Ferrell Gary
Published: October 2013

1000-kHz ultrasonics (megasonics) has been an important technology in controlling killer defects in modern microelectronics. In the construction of, say, a microprocessor, perhaps 10 percent of the 500 process steps may involve acoustically aided cleaning. Feature sizes are currently at 65 nm and will be at 32 nm by 2009. In our laboratory, we have been utilizing multiple-bubble sonoluminescence (MBSL) as a probe into cavitation processes in the hopes of learning to control bubble dynamics and growth. Strong evidence has been found which links MBSL with the removal of 100 nm and larger particles on single-crystal silicon substrates during wafer cleaning. Improved understanding of the bubble interaction with the surface features must be developed in order to maximize cleaning and eliminate damage to nanoscale features. Surface tension modification, overpressure, and nucleation control are some of the experimental controls being developed. A novel nanoscale optical damage probe is in development to further aid in understanding the forces impinging on surface features.
The influence of ultrasound power on multibubble sonoluminescence intensity from aqueous solutions containing surface active solutes
Authors: Sunartio Devi , Ashokkumar Muthupandian , Grieser Franz
Published: October 2013

Water soluble surface active solutes have been found to affect the intensity of multibubble sonoluminescence (MBSL) in aqueous solutions. For example, the presence of charged surfactants enhances the MBSL intensity relative to that observed from pure water, whereas the presence of volatile surface active solutes decreases the MBSL intensity in reference to pure water [J. Phys. Chem. B 101, 10845 (1997)]. Further investigations on how ultrasound power influences the effect of surface active solutes on MBSL intensity have shown that ultrasound power plays an important role in governing the above mentioned effects. The relative enhancement in MBSL intensity by charged surfactants has been found to vary with changes in ultrasound power level; the relative enhancement decreases with an increase in the ultrasound power level. Also, the extent of MBSL quenching by alcohols has been found to increase with an increase in the applied ultrasound power level; no SL quenching at lower power levels and >80% SL quenching at higher power levels have been observed. The influence of ultrasound power on the population of ‘‘active’’ bubbles and the cavitation bubble temperature, in aqueous solutions containing surface active solutes, will be discussed in order to rationalize the observed experimental data.
Viscothermal wave propagation, including acousto-elastic interaction
Authors: Beltman Willem
Published: October 2013

Standard wave equation models neglect the effects of viscosity and thermal conductivity on acoustic wave propagation. For wave propagation in narrow tubes or thin layers, like in MEMS devices, this might not be accurate. This presentation outlines models that take the effects of inertia, viscosity, thermal conductivity and compressibility into account. Three classes of models are described and characterized based on the use of dimensionless parameters. The most important parameter is the shear wave number, an unsteady Reynolds number that indicates the ratio between inertial and viscous effects. It is shown that for most applications the low reduced frequency model is sufficient and the most efficient. The wave propagation models are coupled to the structural models to capture the acousto-elastic interaction. For simple geometries, analytical solutions can be found for these coupled analysis cases. For more complex geometries, a finite element model was developed, based on the low reduced frequency model, in which viscothermal acoustic finite elements are coupled to structural elements. Examples of applications are presented.
An all surface-machined MEMS microphone
Authors: Elko Gary W. , Pardo Flavio , Lopez Daniel , Bishop David
Published: October 2013

An all-surface machined MEMS microphone for telephony applications was constructed a few years ago at Bell Labs. This microphone was built-up from multiple layers of standard polysilicon. After etching, the polysilicon layers were mechanically actuated in an origami-like fashion, to form a condenser microphone shaped in a tetrahedral structure. The overall size of the microphone was roughly 300 μ on a side. The enclosed back reference volume was designed in concert with a unique multiple cantilever beam design to realize a diaphragm resonance frequency of approximately 20 kHz. A discrete component preamplifier based on a modulated carrier detection circuit to reduce 1/f preamplifier noise was constructed. The predicted overall noise level of the microphone was approximately 45 dBA. The measured noise was significantly higher, due most likely to stray capacitance of the lead wires to the external discrete preamplifier. Some design issues related to mechanical-thermal noise will be discussed and some suggestions to mitigate self-noise will be given.
Fluid–structure waves in a micromachined variable impedance waveguide
Authors: White Robert , Deo Niranjan , Grosh Karl
Published: October 2013

A micromachined fluid–structure system, intended to demonstrate a unique cochlear-like acoustic sensing scheme, has been fabricated and analyzed. The system consists of a 0.11-mm-deep Pyrex fluid chamber, anodically bonded to a silicon structure housing a tensioned membrane. The membrane varies in width from 0.14 to 1.82 mm. Both isotropic LPCVD silicon nitride membranes and orthotropic nitride/polyimide membranes have been fabricated. Silicone oils of either 5 or 20 cSt viscosity are used. Laser vibrometry measurements show strong fluid–structure traveling waves. Wave speeds are between 50 and 300 m/s in the 4- to 35-kHz band. These traveling fluid–structure waves exhibit maximum structural motion at a location determined by their frequency. Wave decay rate is influenced by the viscosity of the fluid and, after the waves become evanescent, by membrane orthotropy. Results from finite element computations of an orthotropic membrane coupled to a compressible viscous fluid are compared with experiment. The fluid is modeled using either a two-dimensional thin-film approximation or the three-dimensional linearized Navier–Stokes equation. Both models accurately predict the observed fluid–structure response. Nondimensional parameters controlling system performance, and regions of applicability of the models, will be discussed. [Work supported by ONR, NIH, and NSF.]
A theory for flexural vibration of thin plates with thermoelastic damping
Authors: Norris Andrew
Published: October 2013

Thermoelastic damping in thin plates can be the dominant loss mechanism under certain circumstances, e.g., as demonstrated by recent measurements for MEMS paddle oscillators. However, modeling of thermoelastic damping in flexural vibration of plates has lagged, despite the classical theory of Zener for beams. This talk shows how the thinness of the plate permits a very accurate approximation to the fully coupled system of stress and temperature. In this asymptotically valid theory, the flexural plate equations are modified by damping terms of two types. The first are viscosity-like terms in the plate equation of motion. These depend on the local curvature, being zero at saddles. The damping also modifies the boundary moment and shear force. Both the bulk and boundary effects are important in estimating the Q for resonant modes. The theory is derived from a generalized form of Hamilton’s principle, using Kirchhoff’s kinematic assumption and asymptotic approximations for small thermal coupling valid for all relevant materials. Modal damping can be estimated simply for certain boundary conditions, including fixed edges. Plates with free or partially free edges present a more interesting challenge, and various alternative estimates of Q are presented and illustrated numerically for rectangular plates and MEMS structures.
A search for listener differences in the perception of talker identity
Authors: Remez Robert E. , Wissig Stephanie C. , Ferro Daria F. , Liberman Kate , Landau Claire
Published: October 2013

Talkers differ along several dimensions that listeners can resolve. These include acoustic effects of native variation in the scale and shape of the articulatory anatomy, and the effects of age and use on the tissues of the vocal tract. Linguistically, talkers differ in phonetic habits occasioned by dialect and idiolect, and differ paralinguistically in manner of affective expression conveyed vocally. However, listeners are themselves likely to vary in sensitivity to intertalker variation. In this study we aimed to identify differences in sensitivity to talker variation as a function of linguistic experience. Speech samples were produced by female talkers 15–17 years old drawn from two dialect groups, one from Brooklyn, NY, and one from Bloomington, IN. Each talker produced sentences in a list-reading task. Listeners in our tests were also native either to Brooklyn or to Bloomington, and each was far more familiar with one dialect than the other. Tests of apparent similarity of talkers in each set were conducted with listeners from the same and different dialect group. The results of similarity scaling analyses calibrate the contribution of sensitivity to idiolectal contrast within and across dialect in the perception of a talker’s characteristics. [Research supported by NIDCD.]