bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated signal excess as a metric for environmental acoustic assessment
Authors: Fabre J. Paquin
Published: September 2008

Signal excess (SE) is often used as a metric for determining acoustic performance through a waveguide or over an area. This quantity can limit the capability to assess the environment because SE is computed given a single acoustic source, receiver and frequency, and is a function of range from the source, thereby limiting the scenarios for which the environment can be assessed as well as the ability to visualize it over an area. Integrated SE (ISE) with phase tracking is proposed as an improved metric for evaluation of acoustic performance. For a given source location (in latitude and longitude), the SE is integrated over all possible source depths, a band of frequencies, and bands of ranges. Additionally, the phase variations across the regions are tracked. This metric is compared to various traditional SE fields and is shown to provide a better representation of the overall acoustic properties of a waveguide and an area. The ISE and the original SE are also examined across an ensemble of sound speeds and the variations of the acoustic environment are characterized. [The author appreciates and acknowledges the funding support from the Naval Research Laboratory Base Program.]
Modeling surface duct precursors for Littoral Acoustic Demonstration Center 2003 (LADC03) seismic calibration experiment
Authors: Tashmukhambetov Arslan M. , Ioup George E. , Ioup Juliette W. , Sidorovskaia Natalia A.
Published: September 2008

In summer 2003, LADC conducted a seismic calibration experiment for a 3190-in3 21-element seismic exploration array. After calibration, absolute broadband (up to 25 kHz) pressure-time dependencies for a wide range of offsets and arrival angles were produced. A computational workflow, combining the upgraded version of the Navy standard acoustic propagation model RAM and industry airgun modeling packages, was developed to model the calibrated experimental data. Experimental and modeled data have demonstrated good agreement in absolute pressure amplitudes and large-scale frequency interference pattern for the frequencies up to 1,000 Hz. The results of the application of the developed workflow for investigation of the effect of a seasonally-formed surface duct on seismic array energy distribution is presented. The presence of the surface duct is experimentally confirmed to be responsible for the generation of a unique set of modes forming the precursor arrivals, first systematically observed from a point source on a near-bottom hydrophone by DeFerrari and Monjo. The influence of a range-dependent environment on precursor stability is addressed. An attempt to identify precursors in the LADC03 experimental data is discussed. [Research sponsored by the Industry Research Funding Coalition and the Joint Industry Project.]
Efficient modeling of range-dependent seismo-acoustics problems
Authors: Collins Michael D. , Jung Woo-Yeol , Kusel Elizabeth T. , Siegmann William L.
Published: September 2008

The parabolic equation method is the most effective approach for solving range-dependent problems in ocean acoustics. During the past three decades, many difficulties have been encountered while attempting to generalize this approach to problems involving elastic layers. With the development of an improved single-scattering solution [J. Acoust. Soc. Am. 121, 808813 (2007)], a large class of range-dependent seismo-acoustics problems can now be solved accurately and efficiently. Previous single-scattering solutions for seismic problems were based on an iteration formula, and limited by convergence problems. Since the improved solution does not require iteration, it provides the efficiency of the energy-conserving solution that has proved to be very useful for acoustics problems. The application of this approach to problems involving fluid layers is currently being investigated. [Work supported by ONR.]
Mode formulas for shallow water waveguides using a modified asymptotic approximation
Authors: Kaczkowski Stephen V. , Siegmann William L. , Pierce Allan D. , Carey William M.
Published: September 2008

Sound speed profiles in shallow water waveguides are small deviations from isospeed and often decrease monotonically with depth. Approximation formulas for the propagating modes are found using a modified form of the classical WKBJ method. The ocean bottom is taken as homogeneous. The approach is accurate for modes with phase speeds greater than, and even slightly less than, the maximum water sound speed. The validity and accuracy of the approximations over frequency and mode number are illustrated using benchmark numerical calculations. Comparisons with approximations from other methods, including previous WKBJ approaches, are described. The formulas here are typically more compact and convenient. The results demonstrate how changes in parameters, such as frequency, bottom sound speed, and water sound speed profile quantitatively affect the mode functions. Applications for representative waveguide profiles are provided. [Work supported by the Office of Naval Research.]
Model for energy consumption by a broadband shallow-water acoustic communications network
Authors: Rouseff Daniel , Fox Warren L. J.
Published: September 2008

A multistatic active sonar system with several widely distributed sensors must share information between the sensors. Acoustic communication is a viable method to share information and is particularly appropriate when the sensors are mobile. A potential drawback is that a significant fraction of the total energy budget for the system might be consumed just by sending information between the sensors. In the present work, an energy consumption model is developed that is appropriate for incoherent acoustic communication in shallow water. The model builds upon the foundation established by Sozer et al. [IEEE J. Oceanic Eng. 25, 72–83 (2000)], but uses an improved sub-model for acoustic propagation. The sub-model includes environmental factors like the sound speed profile in the water column and the composition of the seabed. By exploiting the waveguide invariant concept, the broadband nature of the communications signals can be included efficiently in the calculation. Numerical results demonstrate how relaying messages between intermediate sensors can save substantial energy compared to direct communications. The calculations also show that energy consumption can vary by more than an order of magnitude depending on the seabed composition. [Work supported by ONR.]
Relating X-waves and Cerenkov radiation
Authors: Walker Shane C.
Published: September 2008

X-waves are shown to be related to Cerenkov-Vavilov (CV) radiation as derived by solving the linearized inhomogeneous scalar wave equation in free space for the case of a source in uniform motion at velocity v that is greater than the speed of waves, c, in the medium, ‖v‖>c. The results apply to wave phenomena in general, both acoustic and electromagnetic. In this context, the supersonic/superluminal properties of X-waves are unambiguously demonstrated to be phase effects. One implication is that even the ideal diffractionless X-wave is not signal-like nor can it exceed the Shannon data rate bandwidth relation, ΔtΔω=2π. Further, it is shown that the continuous power required to propagate an X-wave is analogous to the energy dissipation of a CV particle caused by radiation drag. Thus, generating a diffractionless X-wave requires an infinite total energy input over a spatially infinite source aperture. Finally, the connection between CV radiation and X-waves suggests the possibility of generating X-waves using time-reversal.
Fictional timbre—Close microphones and warped perspectives
Authors: Case Alexander U.
Published: September 2008

Recording engineers, particularly in pop and rock genres, have a long tradition of placing microphones exceptionally close to the sound sources they wish to record. Not a gesture towards realism, close microphone techniques are born of practical needs for sound isolation in sometimes cramped recording spaces, production pressures to defer signal processing decisions until the mixdown session, and creative desires to variously avoid, enhance, and/or exaggerate sonic features of the instrument in search of a sound that is ‘‘better than the real thing.’’
What to do with a five-track woodwind quintet
Authors: Beauchamp James W. , Bay Mert
Published: September 2008

Recently we made a five-track recording of a woodwind quintet using a two-step process: First, the group was recorded together in the same room with each instrument close-miked. Second, each instrument was recorded separately with the performer monitoring the others on headphones. There were a few synchronization problems, but basically the method worked fine, and the result is a recording with complete separation between the tracks. Although this was inspired by the necessity for ground truth for a demixing project, several other advantages of this approach to recording have come to mind: (1) Listening to all instruments played back simultaneously from separate speakers is very enjoyable. (2) Music-minus-one recordings are useful for musicians to practice with and are easy to produce. (3) Data reduction on each track enables analysis, modification, and resynthesis projects of various sorts. For example, pitch, tempo, relative loudness, and timbre are easy to manipulate. Examples of music produced by processing the woodwind quintet will be demonstrated.
Making outdoor acoustic venues ‘‘better than the real thing.’’
Authors: Harght Pamela
Published: September 2008

Traditionally-acoustic music organizations, particularly orchestras, are developing new ways to reach out to a wider audience, extend their season, and promote their music in non-traditional summer homes. Many of these outdoor venues accommodate far more patrons than the established, enclosed concert hall. Furthermore, with these larger venues comes the responsibility to enhance the performing group through amplification to satisfy the expectations of the patrons and to compensate for the vastly different atmosphere regular concert-goers are accustomed to. Electronic reinforcement is now required to accommodate the thousands more outdoors and with digital reverberation and modern recording equipment, these goals and expectations can be met with little compromise in the listening experience. This paper will discuss the role of sound reinforcement in orchestral music, focusing on the popular Tanglewood Music Center, the summer home of The Boston Symphony Orchestra, and other successful venues.
Pulse and swing: Quantitative analysis of hierarchical structure in swing rhythm
Authors: Lindsay Ken , Nordquist Pete
Published: September 2008

Swing feeling in music is generally attributed to the presence of timing variations in the rhythm as played, contrasted with standard tablature form. Substitution of triplet subdivision for the divide by two format (quarter, eighth, sixteenth notes) of Mozart-Bach (MB) notation is a well known timing variation associated with Swing. We present evidence that an important part of Swing is also found in nonuniform timing of the Pulse, or basic beat, of a Swing tune i.e., time delta between downbeats of successive musical measures does not conform to a regularly spaced time grid as defined by the metronome. To our knowledge, this fundamental aspect of Swing has not been previously reported. The departure from a uniform time grid and presence of different types of time variations played by different instruments both make important contributions to the ‘‘lively’’ quality found in Swing style of many genres: Classic Jazz Swing, Pop, Gospel/Soul, Rock and Roll, Samba, etc. Although different rhythms may not be locked together as in MB style, nonetheless they are all highly synchronized. The degree of synchronization corresponds to varying degrees of tight or loose rhythmic style. This also contributes to the ‘‘live’’ feeling in the musical performance.
Reality is not a recording/a recording is not reality
Authors: Anderson Jim
Published: September 2008

The former New York Times film critic, Vincent Canby, wrote all of us have different thresholds at which we suspend disbelief, and then gladly follow fictions to conclusions that we find logical. Any recording is a fiction, a falsity, even in its most pure form. It is the responsibility, if not the duty, of the recording engineer, and producer, to create a universe so compelling and transparent that the listener isnt aware of any manipulation. Using basic recording techniques, and standard manipulation of audio, a recording is made, giving the listener an experience that is not merely logical but better than reality. How does this occur? What techniques can be applied? How does an engineer create a convincing loudspeaker illusion that a listener will perceive as a plausible reality? Recordings will be played.
Audio networks—From the main stage to main street
Authors: Britton Deb
Published: September 2008

In recent years, digital audio networks have become a more and more prevalent means of distributing audio signals. Audio networks are not unique to large, permanently-installed sound systems, but are also used in touring sound, homes, and even some musical instruments. The audio network trend was not sparked by a desire to be on the cutting edge of technology, but to fill some very real needs. Audio technology has been steadily moving from analog to digital, yet the interconnection of the individual components remains in the analog domain. The resultant numerous A/D and D/A conversions can cause signal quality issues, severely limiting the performance of the system. A network provides a common, digital interconnection, and reduces the infrastructure requirements by routing many signals over fewer cables. For the facility owner, the greatest benefit could be the drastic reduction in cabling. For the engineer or system end user, any input to any output routing capability enables the implementation of different system configurations on the fly, and can allow for future expansion, without the need for hardware or wiring changes. For the musician or home studio enthusiast, a networked instrument provides a direct interface to a computer for recording.
A survey of small live music venues of New Orleans
Authors: Woolworth David
Published: September 2008

This survey of small live music venues of New Orleans will summarize aspects of history, capacity, sound reinforcement specifications, and acoustic properties. There will also be information on the factors affecting sound quality for small venues and some examples of ‘‘on the fly’’ problem solving, using available materials and sound processing.
Link-based feature extraction for model-based detection of echolocation calls
Authors: Skowronski Mark D. , Fenton M. Brock
Published: September 2008

Frame-based acoustical analysis of echolocation calls from bats has recently been proposed to improve the robustness of automated call detection. Statistical models, popularized and honed by automated human speech processing research, learn the distributions of call features extracted identically from short overlapping frames of time. A fundamental assumption is that each frame contains at most one echolocation call. In field recordings of bats, this assumption is often violated by the presence of echoes and overlapping calls from multiple bats, which degrade automated detection performance. Simple rules, based on expert knowledge of echolocation calls, were used to follow local spectrogram ridges and to group ridge points into links. Frame-based features were extracted from the links, which may overlap in time, allowing links to be used in the existing model-based analysis paradigm. Improved performance using links is demonstrated for several pathological cases, including conspecific interaction and high-duty-cycle foraging.
Simulating bat echolocation
Authors: De Mey Fons , Reijniers Jonas , Peremans Herbert
Published: September 2008

In accordance with the growing practice of performing acoustical experiments in virtual reality, the acoustic properties of the echolocation system of a number of bat species are characterized in simulation. The head related transfer function (HRTF) and interaural intensity differences (IIDs) from the pinnae and the radiation pattern from the noseleaves are calculated with a boundary-element method. The obtained results are compared to actual acoustic measurements performed on other specimens of the same species. This comparison shows that performing the experiments in virtual reality is a viable alternative to performing measurements on real specimens. It has the additional advantage that the spatial resolution that can be achieved compared to the more commonly used acoustical measurements, is higher. Furthermore, computer manipulation of the virtual morphology model allows characterizing the influence of different head parts on the HRTF and the noseleaf radiation pattern. To illustrate the power of this technique, the effects of different head parts on the HRTF of the phyllostomid bat Phyllostomus discolor are investigated. For this species, it is concluded that the pinna has a larger effect on the interaural intensity difference (IID) pattern than the head itself.
Sound recordings from the 2007 emergence of Brood XIII cicada
Authors: Muehleisen Ralph T.
Published: September 2008

Level calibrated recordings of the Brood XIII 17-year periodic cicadas were made in June, 2007 in River Forest, Illinois. Brood XIII consists of three separate species: Magicicada cassini, M. septendecim, and the more rare M. septendecula. Power spectrum analysis of a 2 min segment of the recording shows a 5.95 kHz resonance with Q≊6, indicative of cassini, and a 5 dB lower resonance at 1.35 kHz with a Q≊13.5, indicative of septendecim. Since other researchers have estimated that the power of septendecim is 20 dB below that of cassini, the high level of the septendecim song suggests that 30 times more septendecim than cassini were singing. Computation of the sound pressure level shows a 2–5 dB variation with a period of 7.5 s, indicative of synchronized chorus singing of cassini.
Design of LabVIEW-based software for insect acoustic research
Authors: Ramalingam Vijay , Fink Tom , Seiner John , Streett Douglas , Lax Alan
Published: September 2008

LabVIEW-based software has been developed for acquiring and analyzing acoustical data from insects under field and laboratory conditions. The following features will be discussed in the presentation: Data acquisition using single or multiple transducers using National Instruments hardware. Timed, threshold, and periodic data acquisition routines. Periodical playback of WAV files or sine waves during data acquisition. Embedded META data information to avoid field notebooks. Real-time saving or deleting acquired data without losing acquisition continuity. Sequential, logical, and automatic file saving routines with time and date stamped file names. Playback of acquired data at different speeds (0≤v≤1), and at different time frames. Compare multiple waveforms (up to four) using synchronized pan and zoom routines. Create annotations, image file, and small segments of the original waveform with a single mouse click. Create spectrograms, FFT, and power spectrums of the acquired data. [Work supported by USDA ARS.]
A vowel identification procedure for gerbils
Authors: Sinnott Joan M. , Mosteller Kelly W.
Published: September 2008

Mongolian gerbils are small rodents with auditory specializations that provide them with excellent hearing in the human speech range. Our lab has previously developed simple go/no-go response procedures to measure gerbil detection and discrimination of human vowels. Here is presented our new identification procedure that uses a two-alternative, forced-choice, left versus right response. The gerbil is tested in a small wire mesh cage that contains a center platform, a light, and two feeder cups left and right of the light. The gerbil begins a trial by mounting the platform when the light flashes. One of two vowel sounds (e.g. /u/ or /i/) then starts repeating at the rate of 1 per sec. The gerbil is reinforced with food if s/he goes to the left feeder cup for /u/, or to the right feeder cup for /i/. Incorrect responses are punished with timeouts. Gerbils easily learn to differentiate the spectrally-dissimilar vowels /u/ versus /i/, and data will be presented on their ability to differentiate more similar vowels such as /a/ versus /ae/. Gerbil identification ability appears related primarily to second formant frequency differences. A video will be shown of gerbils working on the procedure. [Research supported by NIH.]
The substrate vibration generating behavior of Aphaenogaster carolinensis (Hymenoptera: Formicidae)
Authors: Menzel Timothy O. , Marquess Jake R. , Seiner John , Streett Douglas
Published: September 2008

Aphaenogaster carolinensis Wheeler produces substrate vibrations by striking a substrate with its mandible and dragging its mandible across the surface. We have described this behavior and conducted laboratory trials to determine the conditions under which it occurs. Individual strikes were consistent in pattern and duration, but there was great variation in the duration of, and the number of strikes associated with, a single substrate vibration generating event. In laboratory trials, this behavior occurred most frequently in response to confrontation with non-nest mate con-specifics and did not require the presence of a food source or territory to be initiated.
Multibeam sonar observations of near-surface bubbles during a storm
Authors: Weber Thomas C.
Published: September 2008

In October 2006, a reson SeaBat 7125 multibeam sonar (400 kHz) mounted on the drop keel of the R/V Hugh Sharp was used to collect acoustic backscatter from bubbles generated by breaking wind-waves in the Gulf of Maine. The multibeam sonar has a very high spatial resolution, with 256 1.0×0.5 deg beams. The data of interest here were collected as the ship returned to port because of bad weather (sustained 15 m/s wind speed), traveling through the plumes of breaking waves. Data were collected at a ping rate that varied between 5–10 pings/s. These observations show frequent breaking wave bubble plumes extending up to 12 m deep. The data also show that preferential concentrations of bubbles (clusters) were often present. Correlation functions (e.g., the pair correlation) describing the bubble clustering have been extracted from this data, and their affect on acoustic propagation characteristics (sound speed, attenuation) will be presented. [Work supported by ONR Ocean Acoustics.]
Acoustic monitoring of severe weather in the northeast Pacific Ocean
Authors: Nystuen Jeffrey A. , Vagle Svein
Published: September 2008

Wind and rainfall are the principal physical processes responsible for the production of high frequency (1–50 kHz) ambient sound in the ocean. The primary source of the sound is the resonant ringing of individual bubbles created during wave breaking and raindrop splashes. Larger bubbles (?‘ 300 μ diam) quickly return to the surface, while smaller bubbles can be mixed downward many meters. During severe weather, a layer of smaller ambient bubbles forms and effectively absorbs higher frequency (>10 kHz) sound. These processes are revealed in a two-year record of ambient sound recorded from a sub-surface mooring at 50N, 145W in the northeast Pacific Ocean as part of the Canadian SOLAS program. The passive acoustic signal of wind, rain, and ambient bubble clouds are compared to the sub-surface mooring data including data from an upward looking 200 kHz active sonar and a 300 kHz ADCP. The acoustic signatures of light, moderate and heavy rainfall are superimposed on the signature of high wind, demonstrating rainfall detection even in the presence of high wind. [Work supported by ONR, Fisheries and Oceans Canada, and the Canadian CFCAS & NSERC.]
Analyses of broadband and narrowband propagation measurements in Shallow Water 2006 (SW06)
Authors: Knobles David P. , Koch Robert A. , Wilson Preston S. , Duda Timothy F. , Newhall Arthur E.
Published: September 2008

Acoustic measurements were made during the Shallow Water 2006 Experiment near the New Jersey continental shelf in 70–80 m of water. For a portion of the experiment, several L-arrays and a variety of broadband and narrowband sources were deployed for the purpose of investigating the nature of the dispersion of the acoustic propagation in the seabed. A geo-acoustic inversion methodology is used to infer the dispersion from the acoustic measurements in the water column. The waveguide possesses significant inhomogenities in range, azimuth, and time due to bathymetry, sound speed profile fluctuations resulting from internal waves, and variability in seabed properties. Physical oceanography measurements are used in part to obtain the best estimate for a water column description for the analyses of specific acoustic measurements. Various inversion methods along with different propagation models, such as two-way coupled modes and finite element parabolic equation algorithms, are used to obtain an accurate mean description and uncertainty estimates for the properties that control dispersion of the seabed. [Work supported by ONR.]
Inversion of sediment properties from observations of scattering of buried cylinders using subcritical ensonification
Authors: Sanders William , Bibee Dale , Calvo David
Published: September 2008

It is well known that objects buried near the water-sediment interface may be ensonified beyond the critical angle. Although the evanescent portion of surface waves decays rapidly with depth, objects near the surface may reradiate significant amounts of energy, especially at lower frequencies. Moreover, surface roughness may serve as a mechanism for enhancing the penetration of energy at higher angles. This study addresses the viability of inferring and then utilizing geo-acoustic properties from such scattering observations. A synthetic data set is generated for testing inversion using genetic algorithms (using the SAGA toolkit developed by Peter Gerstoft) and by use of a new model for predicting scattering from buried cylinders, target response using matched asymptotics. Distributions of posterior errors in the inverted parameters are presented. [This work was supported in part by the Naval Research Laboratory under program element PE62782N.]
Bottom and sub-bottom roughness effects on coherence and geo-acoustic inversions
Authors: Heaney Kevin D.
Published: September 2008

In this discussion, the effect of bottom and sub-bottom roughness on acoustic propagation in shallow water is examined. Generally in underwater acoustics, the acoustic medium is quantized as a stratified medium, with dominant changes occuring in depth and the range-dependent environmental variability (apart from bathymetry) is neglected. For a few environments presented in this paper, this approximation is quite poor. Scattering from bottom and sub-bottom roughness can lead to loss of signal and is often treated as an anomolous attenuation. Energy scattered from a rough hard bottom or basement is not removed from the water column but instead propagates as incoherent energy reducing the measured coherence and leading. A numerical model that incorporates random bathymetric and sub-basement roughness into the parabolic equation is presented. Comparisons of the effects of roughness will be made for an experiment over Basalt (BASSEX2004) and limestone (CALOPS 2007), both of which are thought to be hard, rough basements, covered with sand. Comparisons of measured and predicted coherence, geo-acoustic inversion results, and eigenspectra will be presented.
A geometric method for calculating the Doppler spreading of surface scattered signals
Authors: Preisig James , Deane Grant , Tindle Chris
Published: September 2008

Recent work has shown that the characteristics of surface scattered high frequency signals can significantly impact the performance of underwater acoustic communications systems in shallow water environments. A combination of high signal intensities due to the focusing of the signals by the curved surface waves and high Doppler spreads due to the motion of the surface waves make it difficult to accurately track the time varying channel impulse response as required by most high rate communications systems. However, algorithms that can model and accommodate the Doppler spreading have been shown to maintain acceptable performance in these environments. The ability to predict the expected Doppler spreads of the surface scattered signals as a function of source/receiver geometry and surface wave characteristics can improve the performance of some of these algorithms. A method for calculating the Doppler spreading of surface scattered signals as a function of the source/receiver geometry and surface wave slope, curvature, and velocity is presented. Comparisons between theoretical predictions and observed Doppler spreads in collected acoustic data are presented.
Low frequency enhancement of water-to-air sound transmission
Authors: McDonald B. Edward , Calvo David
Published: September 2008

Low-frequency acoustic radiation into the air from an underwater point source is investigated using plane wave expansion of the source spectrum and Rayleigh reflection/transmission coefficients in order to clarify a recent claim of ‘‘anomalous transparency’’ of the water-air interface at low acoustic frequencies [Phys. Rev. Lett. 97, 164301, 2006]. Carrying the analysis to first order in the air/water density ratio, it is found that as the depth-wave number product kD becomes small, radiation into the water is quenched by the source’s acoustic image, while the power radiated into air increases to about one percent of the power that would be radiated into unbounded water. For kD less than about 0.093, a majority of the one percent surviving total energy is transmitted to the air. In our view it seems an exaggeration to refer to this as ‘‘anomalous transparency.’’ [Work supported by the Office of Naval Research.]
Resolving travel-time variability of the coupled oceanographic-tomographic analysis and prediction system (COTAPS)
Authors: Lucifredi Irena , Stein Peter
Published: September 2008

It has been suggested that the tomographic approach that feeds the 8–11 kHz ocean acoustic measurements into an ocean model using data from bottom-mounted hydrophones, suffers from a significant travel-time variability due to the surface waves. In this work, the influence of the ocean surface motion on the acoustic travel times has been studied using both the experimental data collected at the Pacific missile range facility (PMRF) off Kauai, and an appropriate acoustic model. The ray-based acoustic model developed is an adaptation of the range-dependent version of Bellhop with the modified top surface characterizing ocean surface waves. The model-generated time series suggests a direct relationship between the phase of the top surface wave and the time-of arrival, which is further confirmed by the experimental data. Furthermore, an approach is developed that automatically decouples the effect of the top surface waves from the environment-related phenomena, making it possible to assign the travel time variations produced by the physical phenomena independently of the surface geometry, in turn eliminating the surface related error. [Work supported by the ONR.]
Novel method of measuring sound from footfall to understand impacts in space below
Authors: Pettyjohn Steven D.
Published: September 2008

Sound generated by people walking overhead made a conference room and law library unusable in the offices of a lawyer. Employing sound transmission class (STC) and impact insulation class (IIC) test procedures to quantify sound impacts in the space proved useless in understanding the complaints caused by the footfall. That is, the STC ratings and IIC ratings were sufficiently high that complaints would not have been expected. The floor/ceiling assembly was light weight with 28 ft long girders and open web trusses 35 ft long and 24 in. on center. The floor was constructed with two layers of plywood on top, and the trusses and the ceilings were either gypsum board or suspended acoustical tiles. Floors were finished with commercial carpet, vinyl composition tile, and carpet and padding. Short duration sound measurements in the frequency range 12.5 Hz to 10,000 Hz were made to quantify the difference in background sound and footfall generated sound. The very large differences in sound pressure levels at individual one-third-octave band frequencies and the A-weighted sound level clearly shows why complaints would be expected. The influence of floor and ceiling finish is seen in these measurements. The results provide clues to solutions to the problem with the assembly.
Evaluation of field impact sound pressure levels as a function of tapping machine location
Authors: LoVerde John J. , Dong D. Wayland
Published: September 2008

Field impact sound insulation in the United States is typically quantified in terms of field impact insulation class, which is defined in ASTM E1007. This standard requires averaging the receiving room impact sound pressure levels (ISPL) generated by the tapping machine in four defined positions. In a previous paper [LoVerde and Dong, J. Acoust. Soc. Am. 121, 3113 (2007)] the authors analyzed several hundred field tests to determine effects of reducing the number of tapping machine positions on the FIIC rating. In this paper the analysis is extended to look at the detailed effects on the third-octave band ISPL, which may impact design decisions more than the overall FIIC rating. The effect of reducing the number of positions as a function of assembly construction is also examined.
Field impact isolation testing failures due to lowest frequency performance deficiencies
Authors: Hale Marlund E.
Published: September 2008

There is a continuing demand in the construction of multifamily residences and in the renovation of apartments and condominiums to install hard-surfaced flooring in upper level dwelling units. Some municipalities and/or homeowners’ associations have enacted regulations requiring that floor/ceiling assemblies meet specific minimum laboratory tested and/or field impact insulation performance standards. This paper presents field performance test results for several new and renovated condominiums in different multifamily residential buildings that failed both regulatory and homeowners’ association impact performance requirements. Further investigations and research into tests by others indicated that an inordinate number of new and renovated condominiums are failing the FIIC performance requirements only in the lowest test band frequency. Potential reasons for such failures are discussed and remedies are recommended.
Spatiotemporal response of mammalian cells to sonoporation measured using calcium imaging
Authors: Kumon R. E. , Deng C. X.
Published: September 2008

Sonoporation, ultrasound-induced plasma membrane poration, permits the passage of extracellular agents into the cytoplasm that may otherwise be impermeable, thereby making it useful for drug and gene delivery. Ca2+ is an important second messenger (signaling) molecule found to play a role in cell recovery after sonoporation. To better understand the dynamical responses of cells to sonoporation, calcium imaging of Chinese hamster ovarian cells was performed using digital video fluorescence microscopy and the Ca2+-indicator dye fura-2AM. Spatiotemporal evolution of intracellular [Ca2+]i was determined from real-time fluorescence measurements of cells in the presence of OptisonTM microbubbles and various extracellular [Ca2+]o levels before, during, and after exposure to 1 MHz ultrasound tone bursts (0.2 s, 0.45 MPa). In cells where ultrasound caused a direct microbubble-cell interaction, breaking and eventual dissolution of the microbubble were observed with concomitant permeabilization of the cells to Ca2+. These cells exhibited a large influx of Ca2+, and sometimes the [Ca2+]i did not return to its equilibrium level. Subsequently, other surrounding cells often exhibited complex [Ca2+]i dynamics, including intracellular oscillations and intercellular waves. Efforts to model the time evolution of [Ca2+]i in individual cells with analytical and numerical approaches will also be discussed. [Work supported by ACS and NIH.]
Acoustic hemostasis: Underlying mechanisms
Authors: Vaezy Shahram , Crum Lawrence , Carter Steve , O’Keefe Grant , Zderic Vesna , Martin Roy , Karmy-Jones Riyad
Published: September 2008

Cessation of hemorrhage using extrinsic, interventional methods is possible with delivery of energy to bleeding tissues, i.e., cauterization. High intensity focused ultrasound (HIFU) is one such method, with significant advantages of delivering high levels of energy to well-defined regions of deep-seated tissues, even during profuse bleeding. The physical mechanisms involved in this process include thermal and mechanical effects of HIFU, leading to various biological effects. Our results using HIFU devices of 1–5 MHz, and focal, derated intensities of 1,000–10,000 W/cm2, in solid organs such as liver, spleen, and kidneys and major and minor blood vessels, show that temperature of targeted tissues reaches 70–100°C within seconds, with formation of microbubbles, approximately 5−−200 μ in size, and concentration of 100 bubbles/mm3. It appears that boiling of interstitial fluids and blood and acoustic cavitation are both involved. The biological effects include coagulative necrosis, mechanical disruption of tissue structure potentially leading to release of tissue factors enhancing the coagulation, coagulum and thrombus formation at a wound site, tissue fusion via collagen and elastin remodeling, and fibrin plug formation, with minimal damage of the surrounding tissues. These mechanisms appear to provide an effective and safe method of hemorrhage control. [Work supported by NIH, DoD, NSBRI.]
Temporary blood-brain barrier disruption via focused ultrasound for targeted drug delivery in the brain
Authors: McDannold Nathan
Published: September 2008

The ability to deliver drugs to the central nervous system is severely limited by the presence of the blood-brain barrier (BBB). This barrier normally serves to protect the brain and restricts the passage of most molecules from being delivered to the brain tissue from the blood stream. We have developed a method by which the BBB is temporarily disrupted in localized regions using low-power ultrasound pulses combined with a circulating ultrasound contrast agent. By systematically focusing at multiple overlapping locations, one could prescribe the region in which the BBB is disrupted to conform to a desired target volume, reducing drug penetration to the rest of the brain. Ultrasound parameters suited for this procedure are compatible with a device that can focus through the intact skull. In this presentation, we will describe recent research on this technique, discussing methodology, safety, possible mechanisms, and potential means to guide and monitor the procedure.
Influence of inhomogeneity and geometry on lung response to low-frequency underwater sound
Authors: Wochner Mark S. , Zhang Yongjie , Ilinskii Yurii A. , Hamilton Mark F. , Zabolotskaya Evgenia A.
Published: September 2008

An effective medium, finite-element model has been developed for human lung response to low-frequency underwater sound [Wochner et al., J. Acoust. Soc. Am. 121, 3082 (2007)]. Macroscopic properties are determined by averaging over microscopic properties associated with lung tissue elasticity and alveolar geometry. The resulting elastic constants depend on lung volume, and thus vary with the phase of the breathing cycle. This presentation discusses effects due to spatial variations in lung and geometric features specific to the anatomy of lung. An important variation in elastic properties occurs where soft tissue of the parenchyma attaches to much stiffer bronchial tissue, resulting in stresses that may cause injury at high levels of acoustic excitation. A factor affecting inhomogeneity within the parenchyma is the orientation of the swimmer. When vertical, the suspension of the lung under its own weight may cause the stiffness to be higher at the top of the lung than at the bottom, resulting in a change in the lung resonance frequency. Finally, patient-specific geometries based on volumetric data of the human thorax are considered. Results will be presented showing stress and strain fields, lung resonance, and mode shapes. [Work supported by ONR and ARL:UT IR&D.]
Finite-element modeling of microsphere surface modes and high-frequency ultrasound scattering from a single cell
Authors: Falou Omar , Kumaradas J. Carl , Kolios Michael C.
Published: September 2008

A finite-element model of wave propagation using COMSOL Multiphysics (COMSOL Inc., Burlington, MA) was developed to solve the problem of high-frequency ultrasound (10–70 MHz) scattering from spheres. This model is being used to predict ultrasound backscatter from cells for ultrasound tissue characterization. In this work, backscatter from an elastic (polystyrene) microsphere was used to validate the computational model against experimental results. Agreement between experimental results and finite-element solutions were found in the frequency domain solutions. Moreover, conversion of the theoretical solutions to time-domain backscatter data showed good agreement with experimental time domain measurements. To develop a better understanding of the interactions of the incident pressure field with the scattering object, oscillations of the elastic microsphere at various resonance frequencies were also investigated. A systematic relationship between the resonance frequency and its corresponding surface mode was found. An ultrasound scattering model by a single cell is also presented. The model treats the cell as an elastic sphere (nucleus) surrounded by a fluid shell (cytoplasm). Comparison of the theoretical backscatter predicted by the model and experimental measurements for acute Myeloid Leukemia (AML) cell is also shown. Finally, the implications of these results on ultrasound tissue characterization techniques are discussed.
Characterization of trabecular bone structure through acoustic scattering
Authors: Denis Max , Thompson Charles , Chandra Kavitha
Published: September 2008

In this work, observations of the relationship between the internal structure of a three-dimensional trabecular bone and scattering acoustic waves from the bone tissue are investigated. A three-dimensional scattering field base on the perturbation expansion of the fluid and solid constituents of the bone tissue is presented. Due to the anisotropic nature of the trabecular bone, eigenvalues and eigenvectors of the bone tissue’s moment of inertia tensor were used to determine its principal axis. The eigenvector associated with the largest eigenvalue was considered as the unit vector along the principal axis. This allowed for a stationary analysis of the medium. Using spatial autocorrelation, estimates are made of the inner length scales of the medium. Observations were made of the simulated exterior field’s relation to the bone tissue’s inner length scales. Of particular interest are features of anisotropy and frequency dependence of the scattering field.
Fast integral equation algorithm for simulation of acoustic energy transfer to the inner ear through multiple pathways
Authors: Bleszynski Elizabeth , Bleszynski Marek , Jaroszewicz Thomas
Published: September 2008

Recent progress is described in our development of a volumetric integral equation-based algorithm applicable to accurate large scale simulations of propagation of elasto-acoustic waves through inhomogeneous media. The primary goal of our work is to construct an efficient and high fidelity numerical simulation tool for investigating such effects as, e.g., acoustic energy transfer to the inner ear via nonairborne pathways. The considered algorithm achieves high efficiency through the use of an FFT-based nonlossy matrix compression and makes possible rigorous simulations involving realistic geometries characterized by highly subwavelength details, large density contrasts, and described in terms of several million unknowns. The recently added algorithm elements are the node-based Galerkin discretization and the solver extension to include pressure and shear elastic wave propagation. Representative examples of numerical simulations involving several million of unknowns and illustrating the method accuracy and effectiveness in simulating acoustic/elastic field distribution in human head are presented. [Work is supported by AFOSR.]
Extraction of infrasonic waveforms from conventional condenser microphones
Authors: Gabrielson Thomas B. , Marston Timothy M.
Published: September 2008

There are several commercial measurement-grade condenser microphones that are suitable for measurements down to about 0.1 Hz; however, these one-half-inch microphones reach those low frequencies with an in-line attenuator that compromises the overall dynamic range. In a previous paper [T. M. Marston and T. B. Gabrielson, J. Acoust. Soc. Am. 119, 3378 (2006)], a process was described for digital reconstruction of the lowest frequencies that avoids the attenuator and the sacrifice in dynamic range. This work has been extended to evaluate a reconstruction process for a one-quarter-inch condenser microphone, which has significantly higher low-frequency roll-off than the one-half-inch infrasonic microphones. One reason for using the one-quarter-inch microphone is its higher peak pressure limit. By modeling the preamplifier input-impedance bootstrapping and the pressure-equalization leak, extension to a few tenths of a hertz can be performed. However, the pressure-equalization leak characteristic frequency varies from microphone to microphone and with temperature. Consequently, there is a single free parameter that requires a measurement of the actual very-low-frequency response or measurement of a physically constrained reference waveform (like the N-wave from a clean sonic boom). [Work supported by the FAA/NASA/Transport-Canada Center of Excellence for Aircraft Noise and Aviation Emissions Mitigation.]
A device for reducing wind and breaking flow into small-scale eddies to decrease infrasonic noise
Authors: Bedard Alfred J. , Nishiyama Randal T. , Bartram Bruce W.
Published: September 2008

The purpose of the fence developed is to raise the atmospheric boundary layer, and at the same time, break up the wind into small eddies, which interact destructively with one another and rapidly break down into smaller scales. This produces a calm region inside an enclosure or behind a wall with only random weak variations of the wind. Severe weather environments often have strong, complex regional flows. In the past, infrasonic systems have used spatial filters to average out the pressures from boundary layer turbulence. However, such spatial filters, while quite effective at lower wind speeds, do not reduce the wind noise sufficiently at higher wind speeds (e.g., above 10 m/s). This wind noise represented a critical limitation for infrasonic tornado detection systems. To solve this problem, we affixed the tops of barriers with corrugations. These cause the creation of adjacent vortex sheets of opposite signs, which interact strongly with one another and rapidly break down into smaller scales, and will not penetrate into regions behind the barrier. We use the eddy fence in conjunction with porous hose spatial filters. Although our motivation was to extend the effectiveness of infrasonic detectors in high wind conditions, there are numerous other applications.