bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of modal and creaky voice quality variations
Authors: Shetye Avanti S. , Espy-Wilson Carol Y.
Published: October 2013

Voice quality, as a major vehicle of information about physical, phonological, and social characteristics of the speaker, has a vital semiotic role to play in spoken interaction [Laver (1968), Laver and Trudgill (1979)]. In the past couple of years, our lab developed an Aperiodicity/Periodicity/Pitch (APP) detector that produces a spectro-temporal profile of the periodic and aperiodic regions of the speech waveform [Deshmukh et al. (in press)]. To do so, the speech signal is passed through a 60-channel gamma tone auditory filterbank. The distribution of the dips occurring in the average magnitude difference function (AMDF) computed from each channel envelope is analyzed to determine periodicity and aperiodicity. Presently, the APP detector classifies both turbulent noise and irregular vocal fold vibration (creakiness) as aperiodic. In this work, we are investigating the detailed characteristics of the AMDF waveform when speech is creaky. This information is presently being used to distinguish aperiodicity due to turbulence from aperiodicity due to creakiness. We will present results from the refined APP detector using various male and female utterances from the TIMIT database.
Analysis by synthesis of electrolarynx speech
Authors: Saikachi Yoko , Hillman Robert , Stevens Kenneth
Published: October 2013

The ability to accurately synthesize electrolarynx (EL) speech may provide a basis for better understanding the acoustic deficits that contribute to its poor quality. Such information could also lead to the development of acoustic enhancement methods that would improve EL speech quality. This effort was initiated with an analysis-by-synthesis approach that used the Klatt formant synthesizer to study vowels at the end of utterances spoken by the same subjects both before and after laryngectomy (normal versus EL speech). The temporal and spectral features of the original speech waveforms were analyzed and the results were used to guide synthesis and to identify parameters for modification. EL speech consistently displayed utterance-final fixed (mono) pitch and normal-like falling amplitude across different vowels and subjects. Subsequent experiments demonstrated that it was possible to closely match the acoustic characteristics and perceptual quality of both normal and EL speech with synthesized replicas. It was also shown that the perceived quality of the synthesized EL speech could be improved by modification of pitch parameters to more closely resemble normal speech. Some potential approaches for modifying the pitch of EL speech in real time will be discussed. [Funded by NIH Grant R01 DC006449.]
Using on-line altered auditory feedback treating Parkinsonian speech
Authors: Wang Emily , Verhagen Leo , de Vries Meinou H.
Published: October 2013

Patients with advanced Parkinson’s disease tend to have dysarthric speech that is hesitant, accelerated, and repetitive, and that is often resistant to behavior speech therapy. In this pilot study, the speech disturbances were treated using on-line altered feedbacks (AF) provided by SpeechEasy (SE), an in-the-ear device registered with the FDA for use in humans to treat chronic stuttering. Eight PD patients participated in the study. All had moderate to severe speech disturbances. In addition, two patients had moderate recurring stuttering at the onset of PD after long remission since adolescence, two had bilateral STN DBS, and two bilateral pallidal DBS. An effective combination of delayed auditory feedback and frequency-altered feedback was selected for each subject and provided via SE worn in one ear. All subjects produced speech samples (structured-monologue and reading) under three conditions: baseline, with SE without, and with feedbacks. The speech samples were randomly presented and rated for speech intelligibility goodness using UPDRS-III item 18 and the speaking rate. The results indicted that SpeechEasy is well tolerated and AF can improve speech intelligibility in spontaneous speech. Further investigational use of this device for treating speech disorders in PD is warranted [Work partially supported by Janus Dev. Group, Inc.].
Imitation of contrastive lexical stress in children with speech delay
Authors: Vick Jennell C. , Moore Christopher A.
Published: October 2013

This study examined the relationship between acoustic correlates of stress in trochaic (strong-weak), spondaic (strong-strong), and iambic (weak-strong) nonword bisyllables produced by children (3;0-5;0) with normal speech acquisition and children with speech delay. Ratios comparing the acoustic measures (vowel duration, rms, and f0) of the first syllable to the second syllable were calculated to evaluate the extent to which each phonetic parameter was used to mark stress. In addition, a calculation of the variability of jaw movement in each bisyllable was made. Finally, perceptual judgments of accuracy of stress production were made. Analysis of perceptual judgments indicated a robust difference between groups: While both groups of children produced errors in imitating the contrastive lexical stress models (∼40%), the children with normal speech acquisition tended to produce trochaic forms in substitution for other stress types, whereas children with speech delay showed no preference for trochees. The relationship between segmental acoustic parameters, kinematic variability, and the ratings of stress by trained listeners will be presented.
Coarticulatory evidence in stuttered disfluencies
Authors: Arbisi-Kelm Timothy
Published: October 2013

While the disfluencies produced in stuttered speech surface at a significantly higher rate than those found in normal speech, it is less clear from the previous stuttering literature how exactly these disfluency patterns might differ in kind [Wingate (1988)]. One tendency found in normal speech is for disfluencies to remove acoustic evidence of coarticulation patterns [Shriberg (1999)]. This appears attributable to lexical search errors which prevent a speaker from accessing a word’s phonological form; that is, coarticulation between words will fail to occur when segmental material from the following word is not retrieved. Since stuttering is a disorder which displays evidence of phonological but not lexical impairment, it was predicted that stuttered disfluencies would differ from normal errors in that the former would reveal acoustic evidence of word transitions. Eight speakers four stutterers and four control subjects participated in a narrative-production task, spontaneously describing a picture book. Preliminary results suggest that while both stutterers and controls did produce similar rates of disfluencies occurring without coarticulatory evidence, only the stutterers regularly produced disfluencies reflecting this transitional evidence. These results support the argument that disfluencies proper to stuttering result from a phonological deficit, while normal disfluencies are generally lexically based.
Lateral waves at the ocean-bottom interface: A feasibility study for geoacoustic inversion using horizontal arrays
Authors: Pierce Allan D. , Carey William M. , Lynch James F. , Frisk George V.
Published: October 2013

Lateral waves are the cw counterpart of head waves, the latter being sometimes used for geoacoustic inversion [Godin et al., 1999; Berger and Buckingham, 2000; Choi and Dahl, 2004]. They should be detectable at horizontal ranges r that satisfy the criterion H2/(5λ)>r>4h1h2/λ, where the various symbols refer to the water depth, height above bottom of source and receiver, and wavelength in water column. The exent of the usable ranges can be increased appreciably if an end fire (parametic) array is used to direct sound so that the beam hits the bottom interface at the critical angle. Because lateral waves are the diffraction spill-off of energy carried primarily in the bottom, they have the potential for yielding geoacoustic parameters such as bottom attenuation and sound-speed profiles. Textbook models predict waves that radiate up from the bottom at the critical angle; more realistic models suggest a distribution in angles, with the distribution varying with range and depending on the bottom sound-speed profile. Horizontal arrays yield information on this angle distribution. Developed theory uses Biot low-frequency model for the bottom and matched asymptotic expansions.
A blueprint for computational analysis of acoustical scattering from orchestral panel arrays
Authors: Burns Thomas
Published: October 2013

Orchestral panel arrays have been a topic of interest to acousticians, and it is reasonable to expect optimal design criteria to result from a combination of musician surveys, on-stage empirical data, and computational modeling of various configurations. Preparing a musicians survey to identify specific mechanisms of perception and sound quality is best suited for a clinically experienced hearing scientist. Measuring acoustical scattering from a panel array and discerning the effects from various boundaries is best suited for the experienced researcher in engineering acoustics. Analyzing a numerical model of the panel arrays is best suited for the tools typically used in computational engineering analysis. Toward this end, a streamlined process will be described using ProEngineer to define a panel array geometry in 3-D, a commercial mesher to numerically discretize this geometry, SysNoise to solve the associated boundary element integral equations, and MatLab to visualize the results. The model was run (background priority) on an SGI Altix (Linux) server with 12 CPUs, 24 Gbytes of RAM, and 1 Tbyte of disk space. These computational resources are available to research teams interested in this topic and willing to write and pursue grants.
Field testing of sound absorption coefficients in a classroom
Authors: Pettyjohn Steve
Published: October 2013

Formal procedures for determining the sound absorption coefficients of materials installed in the field do not exist. However, the U.S. Air Force requested such tests to prove that the sound-absorbing material used in classrooms at Beale AFB in Marysville, CA, met the specified NRC of 0.80. They permitted the use of two layers of 0.5-in. fiberboard or 1-in.-thick fiberglass panels to meet the specified NRC rating. Post-construction tests showed reverberation times longer than expected. Unrealistic sound-absorption coefficients for room finish materials had to be used with the Sabine equation to achieve agreement between the measured and predicted reverberation time. By employing the Fitzroy equation and generally published absorption coefficients for ceiling tile, carpet, and fiberboard, the model provided excellent agreement with the measured reverberation times. The NRC of the fiberboard was computed to be 0.35, agreeing with published data. Since this did not meet project specifications, the Fitzroy model was used to learn the type and quantity of material needed to meet design goals. Follow-up tests showed good agreement between the predicted and measured reverberation times with material added, and project specifications were met. Results are also compared with the requirements of ANSI 12.60.
An effective method to predict sound transmission loss for multilayered/patterned partitions
Authors: Sinha Siddharth , Lowry Mark , Tarnowski David , Allaei Daryoush
Published: October 2013

Existing methods to calculate the sound transmission loss (STL) of multilayered/patterned partitions require either fabrication of the partition and-time consuming experimental testing or computationally expensive numerical methodologies. This paper presents two fast and accurate methodologies developed using FEM and wave propagation theory to predict the STL curve for any geometrical/material configuration partition. In the first methodology, a FEM program calculates the frequency-dependant bending and shear-wave velocities of any configuration partition by performing a modal analysis on a two-dimensional cross section of the partition. The critical frequency of that partition is then obtained by calculating the frequency at which the wave-speed curve intersects the curve for speed of sound in air. In the second methodology, the critical frequency of the partition is used to obtain an equivalent homogeneous isotropic panel. The separation impedance (mass + bending + shear-wave impedances) of this equivalent panel is calculated to plot the STL curve, which can be considered as that of the original partition as they have similar wave dynamics and critical frequency. The model is experimentally and theoretically validated by comparing a sample of the results with several validated theoretical and experimental trends previously published in open literature.
Recommended noise criteria for siting industrial facilities near residential communities with extremely low ambient sound levels
Authors: Hessler David M.
Published: October 2013

Noise limits or criteria in many residential communities are based on an allowable increase in level above the prevailing ambient sound level, usually on the order of 3 to 5 dBA. The theory is that such a small increase results in masking of the new or existing intruding facility noise by the environmental ambient sound. However, many facilities are planned for installation or already exist in remote and very quiet ambient environments with residual levels as low as 25 dBA during the day or nighttime. This paper summarizes a study conducted to determine appropriate criteria in such remote and quiet areas where little or no noise masking will occur from ambient sources. The paper discusses both audible noise measured by the A-weighted level, low frequency noise characterized by the C-weighted level and tonal noise.
Mitigation of structureborne noise nuisance
Authors: Ko Wing P.
Published: October 2013

This paper presents a noise complaint case which was solved by me a few years ago in Hong Kong. A newlywed couple in the residential unit complained to the Government that the noise emitted from the pump room directly beneath their unit was very annoying, especially in the night-time period. The owner of the building was then required by the Government to mitigate the noise to the night-time statutory noise requirement within 30 days, otherwise he would be prosecuted. Ideally, the structureborne noise from the pump room could be effectively mitigated by installation of floating slab and vibration isolators under the pumps. Also, the water tanks and water pipes were required to be isolated from the walls and floor. However, this work was impossible to be completed within 30 days to stop the prosecution. Water supply to the above residents would be seriously interrupted during the construction period. As the only noise parameter of the statutory requirement was 30 minute A-weighted Leq, the most effective and practical way in this exigent situation was to reduce the pump operation time within any 30 minute period to decrease the Leq values. In addition, the water pipes and pumps were also required to be isolated from the walls and floor with resilient materials to break the vibration channels. These noise mitigation measures were successfully applied to the pump room before the end of the 30 days. Finally, the noise levels inside the complainant’s unit were found to meet the statutory requirement. The noise complaint case was then closed by the Government.
Insertion loss class—Enhancing the single number rating system for duct silencers
Authors: Duta John , Clute Nathan
Published: October 2013

Single number rating systems have been used successfully to select architectural acoustics products for many years. Recently a single number rating system was proposed to evaluate sound attenuators in HVAC applications. The proposed system does not include the very low frequencies. This paper discusses the addition of the 31 Hz octave band to the proposed standard contour for calculating insertion loss class (ILC). A number of examples are shown using actual published silencer test data how the system can be applied to common HVAC noise problems.
Optimization of isolators for vibration suppression in an integrated motor propulsor
Authors: Konde Kiran , Johnson Marty
Published: October 2013

Integrated motor propulsors are ducted propulsors for underwater autonomous vehicles. The noise and vibration created by such propulsors is of great concern for stealth applications. In the present paper, a general approach to the design and optimization of passive elastomers embedded with dynamic vibration absorbers for reducing the vibration of such ducted propulsors will be presented with some results showing the optimal location and dimensions of the isolators. The strong fluid structure coupling between the propulsor, its surrounding duct, annular fluid and the surrounding water is taken into account while designing the isolators. A genetic algorithm with objective function as mean square velocities is used to get the optimal location and optimal size of these isolators. Finally the results obtained from the experiments for the performance of these designed isolators under the operating conditions of the propulsor will be presented. Also the approach adopted will be compared with the vibration control methods available in literature for such applications.
Case study: An appraisal of wet/dry vacuum noise
Authors: Sandman A. E. , Tao Z. , Herrin D. W.
Published: October 2013

An investigation was conducted to assess the difference in sound between a high end wet/dry vacuum and a consumer version. It was noted that the high end model had a convoluted flow path as well as foam in the exhaust. The sound power for each vacuum was measured. Additionally, the sound power for the high end model was measured with and without the foam in the exhaust. As anticipated, the higher end model was better at higher frequencies due to the absorbing material in the exhaust. Additionally, a crude sound quality assessment was conducted. The jury appeared to be more sensitive to the high frequency sound.
An automated system for the acoustical and aerodynamic characterization of small air moving devices
Authors: Schmitt Jeff G. , Nelson David A. , Phillips John
Published: October 2013

A plenum fixture for use in the measurement of acoustic emissions of air moving devices used to cool electronic equipment under the actual aerodynamic conditions of operation has been standardized in ISO 10302 and ANSI S12.11. This fixture has proven to be a valuable tool for use in the characterization of these devices. However, as many in industry have discovered, the construction of the plenum to the standardized specifications can quite complex, and the use of the plenum to fully characterize air moving devices can be quite laborious and tedious. Under contract to the NASA Glenn Research Center, which has a significant interest in the acoustic emissions of the air moving devices it uses to cool racks and payloads that are installed on the International Space Station, the authors have developed a fully automated fan test plenum that operates under software control. This plenum has been developed to facilitate rapid acoustic characterization of fans and other air moving devices, both independently and when operating into real world inlet conditions, obstructions and aerodynamic loads. The plenum slider has been calibrated to allow full development of fan curve data in parallel with acoustic emission data.
Why noise-induced hearing loss of industrial workers is dramatic while that of similarly assessed musicians has been described as trivial
Authors: Bies David
Published: October 2013

Criteria for noise exposure considered acceptable for hearing protection are based upon industrial experience, yet these same criteria do not describe the experience of musicians. Investigation of the physics of the human ear reveals a basic design compromise that explains this anomaly. Acoustic stimulation is encoded in the velocity response of the basilar membrane, which makes possible the use of damping control to achieve the dynamic range of the ear. The use of damping control for this purpose without unacceptable distortions is possible if damping is slowly varying. The ear is free running and guided by previous instruction, making it vulnerable to loud impulsive sounds. To protect the ear the aural reflex is provided, but this protection is limited to frequencies below about 1 to 2 kHz. In the natural environment this design compromise is satisfactory, but in the industrial environment loud impulsive sounds are common and the compromise fails. It is to be noted that impulsive sounds of high frequency and level for which the ear has no defense, and which are not characteristic of music, are averaged to zero using standard assessment procedures.
Noise around electrical energy substations
Authors: Diniz Fabiano B. , Zannin Paulo H.
Published: October 2013

This survey is intended to characterize the noise impact due to electrical energy substations in the city of Curitiba over the population living in their vicinity. This impact has been studied with the aid of a computational tool capable of mapping the acoustical field of substations and their vicinity. Several factors have been considered in this survey: sound power of the transformers; vehicle flow on the surrounding roads; positioning of the firewalls, of the buildings and of the walls; terrain topography. Seven substations have been analyzed, and acoustical maps have been traced for each of them for the day and night periods. With these maps it was possible to visualize what was the incident noise levels on the building facades. The predicted noise levels have been compared to the environmental legislation of the noise emissions in effect in the city. Finally the construction of noise barrier walls surrounding the transformers has been simulated, via the software, for some cases, in order to evaluate the reduction on the acoustical discomfort caused by the transformers over the neighborhood population.
A narrow-band analysis of reflected magnitude and phase from six reflector panel arrays
Authors: Rathsam Jonathan , Wang Lily M. , Torres Rendell R.
Published: October 2013

This investigation analyzes measurements of the reflected sound field from various reflector panel arrays. A previous study by the third author [R. R. Torres and M. Vorlaender, ‘‘Scale-model MLS-measurements of scattering from overhead panel arrays,’’ Acta Acustica (in press)] measured impulse responses using the maximum length sequence method at various receiver positions from six scale-model panel arrays of different sizes and densities. This study included an octave band analysis of reflected magnitude as a function of receiver position. The current authors have extended the research by conducting a narrow-band analysis of magnitude and phase of the reflected sound fields for three of the panel arrays [J. Rathsam, L. M. Wang, and R. R. Torres, J. Acoust. Soc. Am. 117, 2499(A) (2005)]. This study revealed a close relationship between phase and magnitude. The current work continues the analysis of reflected phase and magnitude for the three additional reflector panel arrays. The newer arrays are more complex and may reveal the effects of multiple diffraction more clearly than the previous three arrays.
Wavelet transform use for reflection analysis in architectural acoustics
Authors: Belanger Zackery
Published: October 2013

The use of wavelet transforms in the realm of architectural acoustics is discussed as an alternative to more traditional frequency-analysis techniques. Wavelet transforms allow the time and frequency information of a signal to be viewed simultaneously, providing a valuable way to study the frequency content of individual reflections and the frequency structure of impulse responses. Discussion will focus on the application of wavelet transforms to project work at Kirkegaard Associates.
Development of a new fabric canopy material
Authors: Belanger Zackery
Published: October 2013

The unique requirements of two concert halls, one existing and one new, have driven the development of a new fabric canopy material with beneficial reflection and transmission spectra. The development process is highlighted, including motivation, material choice, testing, and challenges such as absorption issues and architectural requirements. The potential of the fabric for use in other acoustic environments is also discussed.
Whistle repertoire of bottlenose dolphins (Tursiops truncatus) in the Mississippi Sound
Authors: Hernandez Erica N. , Kuczaj Stan , Solangi Moby
Published: October 2013

The whistle repertoire of wild bottlenose dolphins (Tursiops truncatus) in the Mississippi Sound, part of the northern Gulf of Mexico, was investigated. There is a large population of dolphins in this area, and many dolphins that are now housed in zoos and aquariums were captured in the Mississippi Sound. This paper reports the types of whistles that are predominant in this area, and how these whistles are used in the context of concurrent surface behavior. Over the course of 1 year (April 2004–March 2005), dolphin whistles were recorded as part of an ongoing study of the effects of human activity on wild bottlenose dolphins. The surface behavior of the focal group was categorized at 1-min intervals as follows: mill, travel, mill/travel, feed, social, with boat, or with shrimp boat. Whistles were then categorized as one of the following: upsweep, downsweep, convex, concave, sine, or constant frequency. Preliminary analysis of the data suggests that both the rate of whistling and the types of whistles produced vary as a function of dolphin behavior. Further analysis of the data will reveal if different types of whistles are associated with specific surface behavior categories. [Research supported by Department of Commerce.]
Automatic recognition of harmonic bird sounds
Authors: Heller Jason R. , Pinezich John D.
Published: October 2013

The method of sound recognition relies on a transformation of a sound into a spectrogram followed by extraction of the harmonics as curves. The extracted curves are called frequency tracks. A procedure called find—feasible—sets is used to extract sets of tracks that may correspond to harmonic sounds. If a set of tracks overlap each other sufficiently in time, then the set is designated a feasible set. Following the extraction of the feasible sets, the procedure find—maximal—subsets is applied to each feasible set. This procedure uses a function called harmonic—relate that determines if two tracks are harmonically related. All tracks that are not harmonically related to any other tracks in the feasible set are discarded. Furthermore, the feasible set is divided into maximal subsets. A maximal subset is a subset of the feasible set in which every track is harmonically related to one fixed track in the set called the reference track but no other tracks in the feasible set are related to the reference track. Each frequency track in a track set is transformed into a feature vector whose components describe the frequency, slope, and shape of the track. The species of birds analyzed are bluejay and herring gull.
Spectral identification of sperm whales from Littoral Acoustic Demonstration Center passive acoustic recordings
Authors: Sidorovskaia Natalia A. , Richard Blake , Ioup George E. , Ioup Juliette W.
Published: October 2013

The Littoral Acoustic Demonstration Center (LADC) made a series of passive broadband acoustic recordings in the Gulf of Mexico and Ligurian Sea to study noise and marine mammal phonations. The collected data contain a large amount of various types of sperm whale phonations, such as isolated clicks and communication codas. It was previously reported that the spectrograms of the extracted clicks and codas contain well-defined null patterns that seem to be unique for individuals. The null pattern is formed due to individual features of the sound production organs of an animal. These observations motivated the present studies of adapting human speech identification techniques for deep-diving marine mammal phonations. A three-state trained hidden Markov model (HMM) was used with the phonation spectra of sperm whales. The HHM-algorithm gave 75% accuracy in identifying individuals when it had been initially tested for the acoustic data set correlated with visual observations of sperm whales. A comparison of the identification accuracy based on null-pattern similarity analysis and the HMM-algorithm is presented. The results can establish the foundation for developing an acoustic identification database for sperm whales and possibly other deep-diving marine mammals that would be difficult to observe visually. [Research supported by ONR.]
Time and frequency analysis of seismic airgun calibration data from an environmental acoustic recording system (EARS) buoy
Authors: Ioup George E. , Ioup Juliette W. , Chapin Sean R. , Tashmukhambetov Arslan M. , Newcomb Joal J. , Sanders William M. , Walker Christopher D. , Brack Benjamin , Rayborn Grayson H. , Stephens James M. , Sidorovskaia Natalia A.
Published: October 2013

In the summer of 2003 two Environmental Acoustic Recording System (EARS) buoys were deployed in the northern Gulf of Mexico by the Littoral Acoustic Demonstration Center. The buoys were collocated and recorded ambient noise and seismic airgun array shots up to approximately 25 kHz. The gains and hydrophone sensitivities were set such that one EARS buoy could record the seismic shots without clipping and the other could record ambient noise. The M/V Kondor towed an airgun array on parallel linear tracks with horizontal closest points of approach to the buoy of 0, 500, 1000, 2000, and 5000 m, giving experimental data for a wide range of horizontal distances (up to 7 km) and arrival angles. The raw data were calibrated using the EARS system parameters to produce calibrated pressure time series for each shot. These data are analyzed in both the time and frequency domains. Maximum pressures for each shot as well as sound exposure levels (pressure squared integrated over time for 200 ms in this case) are presented. Also presented is a spectrogram analysis. The maximum time-domain peak pressure recorded is 200 dB re: 1 μPa. The maximum sound exposure level is 177 dB re: 1 μPa2 s. [Research supported by Industry Research Funding Coalition.]
Littoral Acoustic Demonstration Center 2003 seismic calibration experiment: Modeling acoustic energy distribution from seismic exploration array
Authors: Sidorovskaia Natalia A. , Tashmukhambetov Arslan , Ioup George E. , Ioup Juliette W.
Published: October 2013

In the summer of 2003 the Littoral Acoustic Demonstration Center (LADC) conducted a calibration experiment to measure the acoustic energy output of an industrial seismic exploration array in a frequency range up to 25 kHz. A standard acoustic propagation model, RAM (Range-dependent Acoustic Model by M. Collins), was adapted to model the broadband (up to 1000 Hz) waveguide transfer function for a 21-element moving seismic exploration source array generating acoustic data. Notional source signatures for each airgun in an array were generated by the calibrated airgun modeling package Gundalf, which is based on original theoretical work by Ziolkowski, Hatton, Laws, and others. The package allows modeling of the very close bubble interactions from each airgun in an array. Experimental and simulated data demonstrate good agreement in the frequency range up to 300 Hz. Factors responsible for the discrepancies between measured and modeled data in the higher frequency region are discussed. Environmental implications of variations in the acoustic energy distribution with seasonal and geographic changes in the propagation environment are addressed. [Research sponsored by the Industry Research Funding Coalition through the International Association of Geophysical Contractors.]
Performance variability of matched-field processors on a shelf-break region in the Mid-Atlantic Bight
Authors: Na Young-Nam , Mignerey Peter C. , Pasewark Bruce H.
Published: October 2013

An acoustics experiment (RAGS) was conducted by NRL in December 2003 in the Mid-Atlantic Bight. The deployed equipment included two sources broadcasting 300- and 500-Hz cw signals and three vertical arrays distributed at 10-km intervals over a 30-km range. The water depth varied between 63-125 m. Temperature profiles were obtained from sensors attached to the vertical arrays. Fourier analysis of temperature and vertical array data show that the region is dominated by the M2 tide, the effects being strongest up slope. Several storms significantly influenced the received acoustic fields. Simulations, using several matched-field processors, show significant mismatches between replica and data fields are introduced by changes in the water depth and the sound speed profiles. Just 1 m of tidal depth changes cause significant phase differences between replica and data fields that induce nearly 20-dB variation in matched-field processor output. The study will apply several existing matched-field processors to the measured data with modeled replicas and discuss source localization results. The discussion will focus on the inevitable degradation of processors that utilize coherence between replica and measured data in shallow waters. [Work supported by the U.S. ONR and the R.O.K. Agency for Defense Development.]
Littoral tidally induced environmental influences on horizontal array performance
Authors: Oba Roger , Finette Steven , Shen Colin , Evans Thomas
Published: October 2013

A modeled continental shelf-break region is used to assess the combined and relative impact of bathymetry and internal wave/bore influences on horizontal array performance in a littoral environment. Tidal forcing over a smooth break varying from a maximum depth of 100-m flat bathymetry to 50 m is used in conjunction with a submesoscale hydrodynamic model to produce internal wave activity in a fully stratified water column. A continuous wave source (100 Hz, for example) is sited at different aspects relative to the shelf break, and the acoustic field is propagated to broadside arrays that are placed at various bearings. A three-dimensional parabolic equation code propagated the field to the arrays. Time-variable three-dimensional acoustic effects such as beam wander due to horizontal refraction, resulting from either slope or internal waves, are both illustrated. The time-dependent bathymetric effects can be either enhanced or reduced by the internal tidal activity, depending upon the relative geometry of propagation, bathymetry, and internal tide. The influence of bathymetry versus the full evolving environment due to hydrodynamic action can be compared using array correlation calculations, signal gain degradation, and beam wander. [This research is sponsored by the ONR.]
Calculation of fine-scale sound-field structure based on towed CTD (conductivity, temperature, and depth) chain measurements
Authors: Lyons Joy E. , Bradley David L. , Culver R. Lee
Published: October 2013

In July 2002, an experiment was conducted off the coast of southern California in which the two-dimensional temperature and salinity field was measured directly using a towed CTD chain. The sensor spacing was smaller (2 to 8 m) near the surface (above 30 m) in order to better resolve the mixed layer and thermocline; the depth of the lowest sensor was about 150 m. The path of each tow was back and forth across the same section of ocean such that ocean dynamic features observed in the CTD data were recorded in expanded and compressed states depending on the ship’s heading. The range of each run was a few kilometers, with data taken in 1-s increments. This yielded a high-resolution field suitable for analyzing the propagation behavior of high frequencies. Using the fine-scale measurements of the sound-speed field and an acoustic propagation model based on an FFT-realized parabolic equation, the sound field was calculated reflecting the observed ocean dynamic features. Modeling of scintillation in acoustic intensity will be discussed in the context of spice theory. [Work supported by ONR Code 321US.]
Principles of radiation force
Authors: Rudenko Oleg
Published: October 2013

A brief review of general problems of radiation force (RF) is given. RF was discovered by Lord Rayleigh in 1902 and further fundamental contributions to the RF phenomenon were made by Brillouin and Langevin. In spite of century-old history, RF has not been studied exhaustively and there are many grey areas. The difference between the Rayleigh and Langevin RF appearing in fluids, the difference between averaging procedure in Lagrange and Euler representations, the connections between mean characteristics of the RF-induced streaming (velocity, pressure, mass transfer) and acoustic parameters are still under discussion. Everyone knows that RF is produced by a change in the density of ultrasonic wave energy due to the absorption or due to the reflection from obstacles and inhomogeneous inclusions. However, can RF appear in lossless homogeneous medium or not? The pumping effect of sound beam caused by hydrodynamic nonlinearity was first discussed more than 50 years ago, and similar effects in biomedical applications RF produced by high-intensity focused ultrasound are being discussed now. The talk reviews recent progress in investigation of the problems concerning RF in fluids, biological tissues, and solids with account for specific properties of wave field like nonlinearity, diffraction, absorption, focusing, and scattering.
In vivo noninvasive method for measuring local wave velocity in femoral arteries of pig
Authors: Zhang Xiaoming , Kinnick Randall , Pislaru Cristina , Fatemi Mostafa , Greenleaf James
Published: October 2013

We have proposed generating a bending wave in the arterial wall using ultrasound radiation force and measuring the wave velocity along the arterial wall [Zhang et al., IEEE Trans. Ultrason. Ferroelectr. Freq. Control 52, 642–652 (2005)]. Here, we report the results of in vivo studies on pigs. The pig was anesthetized, and a micromanometer tip catheter was inserted into the femoral artery to measure luminal pressure. A water bath was created on the animal’s groin to allow unimpeded access of the ultrasound beams to the femoral artery. The femoral artery was first located using a 13-MHz linear-array transducer. Then, a vibro-acoustography image was obtained to ensure precise positioning of the excitation force relative to the artery. The artery was excited by the force transducer and the resulting vibration of the arterial wall was measured by a sensing Doppler transceiver. Measured wave velocity was 3.1 m/s at 300 Hz. With this new method wave velocity over a distance of 5 mm, and therefore stiffness of arteries, can be measured locally and non-invasively. Measurement time is short in a few tens of milliseconds, which allows pressure dependence and pharmacological effect on the wall properties to be measured at different cardiac times.
Vibro-acoustography: Recent advances and future promises
Authors: Fatemi Mostafa , Alizad Azra , Greenleaf James F.
Published: October 2013

Vibro-acoustography is an imaging modality that uses ultrasound as the source of energy to explore objects at two ends of the spectrum. Employing two ultrasound beams at slightly different frequencies, this technique produces a highly localized radiation stress field that vibrates the object at the difference frequency. In response, the object produces a secondary acoustic field. This sound, which contains information about the dynamics of the object at the low difference frequency as well as objects characteristics at the ultrasound range, is used to produce an image of the object. This combination makes vibro-acoustography a unique tool to study biological tissues at low and high frequencies simultaneously. Utility of this method has already been demonstrated for a wide range of applications in vitro. In vivo applications of vibro-acoustography have been demonstrated in a recent study on human breast. It has been shown that this technique can produce high quality in vivo images at ultrasound intensities within the recommended FDA limits. Vibro-acoustography may also be used for imaging solids, such as metallic implants. This paper describes recent achievements in vibro-acoustography as well as possible future role of this technology in medicine. [This abstract includes materials patented by MF and JFG.]
A bioreactor for the dynamic mechanical stimulation of vocal-fold fibroblasts based on vibro-acoustography
Authors: Chan Roger W. , Rodriguez Maritza
Published: October 2013

During voice production, the vocal folds undergo airflow-induced self-sustained oscillation at a fundamental frequency of around 100–1000 Hz, with an amplitude of around 1–3 mm. The vocal-fold extracellular matrix (ECM), with appropriate tissue viscoelastic properties, is optimally tuned for such vibration. Vocal-fold fibroblasts regulate the gene expressions for key ECM proteins (e.g., collagen, fibronectin, fibromodulin, and hyaluronic acid), and these expressions are affected by the stress fields experi- enced by the fibroblasts. This study attempts to develop a bioreactor for cultivating cells under a micromechanical environment similar to that in vivo, based on the principle of vibro-acoustography. Vocal-fold fibroblasts from primary culture were grown in 3D, biodegradable scaffolds, and were excited dynamically by the radiation force generated by amplitude modulation of two confocal ultrasound beams of slightly different frequencies. Low-frequency acoustic radiation force was applied to the scaffold surface, and its vibratory response was imaged by videostroboscopy. A phantom tissue (standard viscoelastic material) with known elastic modulus was also excited and its vibratory frequency and amplitude were measured by videostroboscopy. Results showed that the bioreactor was capable of delivering mechanical stimuli to the tissue constructs in a physiological frequency range (100–1000 Hz), supporting its potential for vocal-fold tissue engineering applications. [Work supported by NIH Grant R01 DC006101.]
Non-dissipative mechanisms of radiation force and shear wave generation
Authors: Ostrovsky Lev , Ilinskii Yurii , Sarvazyan Armen , Sutin Alexander
Published: October 2013

We describe new mechanisms of shear stress generation in tissue by radiation force (RF) that are not related to attenuation or reflection of ultrasound waves. The suggested theoretical model is based on the five-constant theory for elastic solids that is extended to waterlike biological media. It is shown that in the absence of dissipation, a potential and linear sound beam in a homogeneous medium creates a potential radiation pressure rather than the shear stress. However, in inhomogeneous non-dissipative media, that is in a lossless medium with spatially varied linear and/or nonlinear parameters, the shear stress generation by this RF is possible. Additional non-dissipative mechanism is associated with the anharmonicity of the primary beam. Although the corresponding effect is proportional to the third power of the beam amplitude, it can be significant in the focal area. Estimates demonstrate that the contribution of the above mechanisms to the value of the generated RF can be comparable with and even exceed the classical dissipative radiation force in realistic situations. Experiments with inhomogeneous tissue mimicking phantoms are presented and experimental results are interpreted in the framework of the above theory. [Work partly supported by NIH grant.]
Radiation force of ultrasound as shear wave source in microscopic magnetic resonance elastography
Authors: Othman Shadi F. , Ozer M. Bulent , Xu Huihui , Royston Thomas J. , Magin Richard L.
Published: October 2013

Microscopic magnetic resonance elastography (micro-MRE) is a high-resolution imaging technique for measuring the viscoelastic properties of small synthetic and biological samples. Taking MRE to the microscopic scale requires stronger static fields, stronger magnetic field gradients, higher performance RF coils, and more compact, higher frequency shear wave actuators. Prior work by our group has been conducted at 11.74 T. A needle attached to a vibrating cantilever beam was placed in contact with the surface of the sample to generate shear waves up to 800 Hz. At higher frequencies, the excited shear waves attenuate within an extremely short distance such that only a very small region in the vicinity of the actuator can be studied due to inherent dynamic range limitations. In principle, modulated focused radiation force of US should be able to create a localized shear wave source within the test sample at a distance from the US transducer, thereby enabling micro-MRE probing of the sample at very high frequencies (up to 5 kHz). A confocal US transducer was fabricated to create such a source within the working constraints of the micro-MRE system. Initial feasibility studies are reviewed in this presentation. [Research supported by NIH Grant No. EB004885-01.]
Finite-difference time-domain approach to acoustic radiation force problems
Authors: Silva Glauber T.
Published: October 2013

Acoustic radiation force plays a major role in elastography methods such as vibro-acoustography, acoustic radiation force, shear wave elasticity, and supersonic shear wave imaging. The radiation force (dynamic or static) exerted on an object by an incident wave can be obtained by solving the acoustic scattering problem for the object. However, only in rather simple cases the scattering of waves can be described by exact analytical expressions. In this work, we developed an algorithm based on the finite-difference time-domain (FDTD) method to compute the radiation force exerted on arbitrary shaped objects. The algorithm simulates the wave propagation in a finite extended medium with an embedded object. The radiation force is obtained by numerically calculating a surface integral of the momentum flux, which depends on the incident and scattered fields. Absorbing boundary conditions are used to truncate the medium. We compute the radiation force exerted on a rigid and soft cylinder by a plane wave. Results are in agreement with the theoretical predictions. Discrepancies due to numerical dispersion in the algorithm are under investigation. The presented method might be used to calculate the radiation force on complex objects present in elastography techniques. [Work supported by FAPEAL/CNPq, Brazil.]
Low-frequency ground impedance from the surface mode
Authors: Waxler Roger , Talmadge Carrick L. , Gilbert Kenneth E.
Published: October 2013

At the last meeting of the Acoustical Society of America we presented data and theoretical analysis showing that pulse arrivals in downward refracting atmospheres have a universal low-frequency tail. This tail was identified with the surface mode. In this presentation we discuss the possibility of obtaining low-frequency ground impedance from the surface mode arrival. Signals received on a 10-m vertical array are analyzed. The vertical waveform of the surface mode is obtained as a function of frequency and used to infer a ground impedance. The inferred ground impedance is compared to impedances predicted by ground impedance models.