bluuebunny/crossref_metadata_2025 huggingface dataset:
Interior Fourier near-field acoustical holography using energy density.
Authors: Collins Zachary A. , Gee Kent L. , Sommerfeldt Scott D. , Blotter Jonathan D.
Published: March 2010

Near-field acoustical holography (NAH) is used to reconstruct three-dimensional acoustic fields from a two-dimensional planar measurement. During previous work at BYU, a method has been developed called energy-based near-field acoustical holography which reduced the number of needed measurements by 75%. Other recent advances have expanded the theory to interior spaces where multiple sources and/or reflections are present. This paper presents a new method for reconstructing interior acoustic parameters using Fourier NAH and a single plane of energy density measurements. Energy density is measured using a six-microphone array. First, the probe measurements are used to create a Hermite surface pressure interpolation on two separate planes. These two planes are used to approximate the normal particle velocity as well as to separate the incoming and outgoing waves using the spatial Fourier-transform method. Once separated, traditional Fourier NAH is used to reconstruct the pressure and normal particle velocity at any point in space. Analytical and experimental results are shown and compared to exterior Fourier NAH approximations. Other drawbacks and benefits are discussed.
Conformal mapping based on spherical array measurements: Noise source identification in a car cabin.
Authors: Haddad Karim
Published: March 2010

Spherical beamforming based on spherical array is a technique well suited for in-cabin noise source identification, especially from mid- to high frequencies. One aspect of these imaging techniques based on acoustic measurements is how to link detected acoustic sources with the environment. Two main alternatives are currently used. The first possibility is based on pictures of the environment: pictures are superimposed on the acoustic map for an easy identification of sources. The main advantages are its quickness for setup and also it is a good solution to efficiently keep track of any change in the environment. The second possibility is the use of a model describing the objects around the microphone array. It is an interesting solution to describe precisely the medium. But also in terms of accuracy, it provides the correct distances from objects to the acoustic sensor: the level of sources could be more accurately determined. This last option can therefore generate an acoustic map conformal to the surrounding environment. In this paper, we use the conformal mapping technique in a case study concerning tests done in a car cabin using a spherical array.
Panel contribution analysis for a large complex structure.
Authors: Mylavarapu Sandeep , Wu Sean F.
Published: March 2010

This paper presents a newly developed panel contribution analysis using the Helmholtz equation least squares method for a large complex structure. The approach requires only one set of the acoustic pressures measured in the near field of a vibrating structure. Using these input data, the normal surface velocity and acoustic pressure are reconstructed, from which the normal acoustic intensity distribution is calculated. Next, the normal acoustic intensity is correlated to the acoustic pressure at any field point of interest. In this way, the relative contributions from individual panels toward acoustic radiation at any field point can be ranked, and the critical panel(s) of a vibrating structure can be identified. Numerical simulations using this approach for identifying critical panels inside a passenger compartment are presented.
Rocket motor microphone investigation.
Authors: Herrera Eric , Pilkey Debbie , Gee Kent L. , Giraud Jarom H. , Young Devin J.
Published: March 2010

Identification of optimal microphone configurations and instrumentation is underway as a continuous process improvement effort at ATK Space Systems, where large solid rocket motors (SRMs) have been tested for decades. Rocket motor tests provide a unique environment which cannot be fully duplicated in a laboratory. This is especially true for the largest SRM ever to be tested, Demonstration Motor I (DM-I), which is the five-segment first stage of the NASA Constellation program’s Ares I launch vehicle. During the DM-I firing, two separate arrays of pressure transducers with various vent tube configurations, microphones, accelerometers, and temperature sensors were placed at locations near the motor. The objectives were to better determine the vibration levels and temperature to which acoustic gages are subjected and to examine their comparative performance for different vent tube configurations, particularly at low frequencies (10–30 Hz). Results from the DM-I and corroborating laboratory tests reveal very different low-frequency responses for the pressure transducers that depend critically on vent tube configuration. This and other issues are discussed.
Condenser microphone protective grid correction for high-frequency measurements.
Authors: Lee Erik N. , Bennett Reginald M.
Published: March 2010

Use of a protective grid on small diameter microphones can prolong the lifetime of the unit, but the high-frequency effects can complicate data interpretation. Analytical methods have been developed to correct for the grid effect at high frequencies. Specifically, the analysis pertains to quantifying the microphone protective grid response characteristics in the acoustic near field of a rocket plume noise source. A frequency response function computation using two microphones will be explained. Experimental and instrumentation setup details will be provided. The resulting frequency response function for a B&K 4944 condenser microphone protective grid will be presented, along with associated uncertainties.
Listening to soundscape as the music of life.
Authors: Cance Caroline , Dubois Danièle , Genevois Hugues
Published: March 2010

The musician M. Shafer introduced, in 1970, the word and the concept of soundscapes as “the tuning of the world,” driving our attention to the quality of the sounding environment, therefore comparable to music. The concept of soundscape has been developed within acousticians’ communities, and the research slowly evolved from “noise effect,” “noise control,” or “noise annoyance” to “sound quality” or “soundscape” and “soundscaping.” Also, around 70 electroacoustics music has promoted every day noises as musical sounds, and nowadays computer music blurs the boundaries between musical instruments and new technological devices and tools. We would like to present here our research conducted in perception and evaluation both in music (and more precisely on digital music) and in everyday noise and soundscapes to discuss some of the following questions: What makes a noise a musical sound? Its acoustic properties? That it is produced by a specific (musical) instrument? The time, places (streets? concert halls?) or ways one hears/listens to it (personal involvement, purpose)? Are the boundaries between music and noise the same in different communities (acousticians, musicians, instrument makers, every one in the street)? How do the concepts of music/noise evolve in time and space, and people?
Model of a benefit/cost ratio analysis for comparison of environmental noise barriers.
Authors: Carvalho Antonio P. , Oliveira Pedro D.
Published: March 2010

The choice for an economically ideal solution of environmental noise barrier must acknowledge both the cost of its main components and the benefits it can provide through time. To achieve a systematic analysis tool an algorithm based on benefit/cost ratio analysis was created. It calculates the benefit/cost ratio for any potential noise barrier. The cost of a barrier can be described with known or quantifiable parameters such as barrier height, thickness, angle, material and initial investment costs, life-cycle costs as maintenance costs, replacement costs due to minor/major accidents, vandalism or defacement, etc. The benefits associated with a solution are defined by computable parameters such as sound absorption index (DLalfa) and airborne sound insulation index (DLr) defined in EN 1793, insertion loss (predicted or measured), and even intangible parameters such as visual intrusion (color and aesthetics) and environmental impact (sustainability). Each benefit is weighed regarding its importance. Using the necessary parameters it is possible to calculate the benefit/cost ratio for any number of years of a life expectancy. An analysis concerning several possible solutions with different life expectancies can therefore be conducted. A general example of application is also presented.
Annoyance response to mapped noise from combined road-traffic and railway system.
Authors: Son Jin-Hee , Park Tae-Ho , Ko Joon-Hee , Chang Seo Il , Lee Kun
Published: March 2010

To study annoyance response to combined transportation noise from road-traffic and railway, a social survey has been performed in a highly populated residential area in the city of Seoul, South Korea. To determine the noise exposure level in an interviewed household, a noise mapping software package was utilized and the noise exposure level from each single source was calculated separately and combined to get total exposure level. The prediction was partially validated by measurements. The households in the study area are classified into acoustically differentiated groups which are named as the road-traffic noise dominant, railway noise dominant, and combined noise dominant, respectively. %HA (percentage of highly annoyed people) curves to noise exposure level are presented for the acoustically classified three groups. Comparison of the %HA curves shows that more people are highly annoyed to railway noise than road-traffic noise, but the curve for combined noise is much closer to the %HA curve for road-traffic noise rather than the %HA curve for railway noise. Multiple-regression and path analysis of the survey data give the direct and indirect quantitative relationships between annoyance and noise and non-noise factors. Personal sensitivity to noise and satisfaction of living environment are primary contributing factors.
Noise mechanisms in motorcycle helmet noise.
Authors: Carley M. J. , Holt N. J. , Walker I.
Published: March 2010

A unique set of results on the acoustics of motorcycle helmets has been gathered during road tests on a rider wearing a representative modern helmet. The data were collected during a study of the noise which can cause hearing damage and, possibly, distraction in riders. They consisted of simultaneous measurements of noise at the rider’s ear and unsteady pressure on the helmet surface, combined with GPS measurements of rider position and speed. These signals have been analyzed to reduce the coherent structures in the turbulent flow responsible for noise generation. The identified structures appear to be produced by a vortex street shed by the motorcycle windscreen. The internal and external pressures proved to be poorly correlated over most of the frequency range, which has been identified as a result of the insertion loss of the helmet. The implications of these findings are that the majority of the variation in helmet noise is a function of such extrinsic factors as motorcycle configuration and rider build and posture. Efforts to reduce the harmful effects of noise in motorcycling should, then, move to studying the whole system of rider, helmet, motorcycle, and external environment.
Calculating annualized sound levels for a wind farm.
Authors: Kaliski Kenneth , Duncan Eddie
Published: March 2010

Modeling done for wind farms usually focuses on calculating a worst-case short term average sound level. However, the impact to homes is not simply defined by a single meteorological condition. Rather, a more complete picture of the impacts is given by calculating sound levels under various meteorological conditions that occur during the year. The actual sound level at a receiver will depend on variations in atmospheric stability, wind speed, wind direction, and other parameters that change hourly. This paper will describe a method to calculate hourly sound pressure levels for individual receivers over the course of an 8760 h year and give examples of different wind farm configurations and how they affect annualized sound levels.
Low frequency sound and infrasound from wind turbines: A status update.
Authors: O’Neal Robert D. , Hellweg Robert D. , Lampeter Richard M.
Published: March 2010

A common issue raised with wind energy developers and operators of utility-scale wind turbines is whether the operation of their wind turbines may create unacceptable levels of low frequency noise and infrasound. In order to answer this question, one of the major wind energy developers commissioned a scientific study of their wind turbine fleet. The study consisted of three parts: (1) a world-wide literature search to determine unbiased guidelines and standards used to evaluate low frequency sound and infrasound, (2) a field study to measure wind turbine noise outside and within nearby residences, and (3) to compare the field results to the guidelines and standards. The guidelines and standards evaluated were audibility including infrasound; ANSI S12.2 for interior sounds—both acceptability of low-frequency sounds in bedrooms, schools, and hospitals and perceptible rattles and vibration; ANSI S12.9 Part 4 for thresholds of annoyance and beginning of rattles; and certain European criteria for low frequency and infrasound. This paper presents the results of the detailed study and concludes that there should be no adverse public health effects from infrasound or low-frequency noise at distances greater than 1000 ft from the wind turbine types measured.
Acoustic sensing for urban battlefield applications.
Authors: Pham Tien
Published: March 2010

For years, acoustic sensor systems have been used effectively in a variety of battlefield applications due to its low-cost, low-power, non-line-of-sight and 360 deg coverage capabilities. Acoustic (only) systems can autonomously detect, track, and classify a variety of targets: personnel, ground vehicles, airborne targets, and transient events. In recent years, acoustics has become an important sensing technology due to its complementary sensing capability within multi-modal sensor systems, and its wide-area coverage capability to alert and point other hi-resolution sensors within a network of sensor systems for intelligent-surveillance-reconnaissance (ISR). For example, in a multi-modal sensor system, acoustic can provide enhanced detection and discrimination of targets and activities, and cue imaging sensors to capture the events of interest. Similarly, in a network of ISR sensor systems, acoustic can reduce the search space for other ISR sensors to autonomously track and locate events of interest in real time. In this discussion, we will present an overview of battlefield acoustic applications that are of current interest to military operations: (i) detection and localization of transients, (ii) sensing from mobile and aerial platforms, and (iii) sensing within a network of ISR sensor systems. We will then discuss the signal processing strategies and challenges associated with the applications.
Associating acoustic transients for localization by multiple arrays.
Authors: Tran-Luu Tung-Duong
Published: March 2010

This paper first presents two methods to estimate the location of an acoustic transient based on measurements of its time-of-arrival and direction-of-arrival at a set of microphone arrays. One is a least-square (LS) estimator, the other a maximum likelihood (ML) estimator. Both are compared to the Cramer–Rao lower bound for reference. They are then extended to associate detections (of the same event) at different arrays by a maximum a posteriori (MAP) formulation that can sort out outliers and multipath detections while re-using the likelihood values computed in the first part. Simulations show that the LS estimator performs slightly better than the ML estimator when the observation noise does not match the noise model. Both methods exhibit a bias in the range estimate, which accounts for most of the square error. The MAP estimator, applied to live fire data, was accurate and successfully resolved simultaneous multiple targets from outlier and multipath noise.
Comparison of the performance of acoustic beamformers under differing atmospheric conditions.
Authors: Collier Sandra L. , Sim Leng , Tran-Luu Duong , Wilson D. Keith , Ostashev Vladimir E.
Published: March 2010

It is well known that atmospheric turbulence can negatively impact the performance of acoustic beamformers. While many beamformers, especially adaptive ones such as minimum variance distortionless response (MVDR), may be robust when the turbulent fluctuations are mild to moderate, they fail when the fluctuations are large. Other methods, such as maximum likelihood estimation, may be used to mitigate the effects of turbulence by directly incorporating the physics of the propagation medium into the assumed model of the acoustic signal (through the covariance and mean). When using synthesized data, the previously developed maximum likelihood estimator (MLE) for the azimuthal angle of arrival was found to outperform classical beamformers. However, in reality the atmosphere does not exhibit the exact behavior of the assumed atmospheric model, or all the required input parameters, such as the meteorological data, for the atmospheric model are not available. Therefore, we compare the performance of methods such as the MLE to that of classical and parametric methods, such as MVDR, multiple signal classification, and matched subspace detector, for data collected during a variety of atmospheric conditions. We critically examine the expense of gained accuracy over computational speed.
Impact of a collection of buildings on line-of-bearing estimates.
Authors: Noble John M. , Alberts W. C. Kirkpatrick , Coleman Mark A.
Published: March 2010

The urban environment presents a very complex environment for the propagation of acoustic signals. To study some of these effects, a series of field experiments was conducted looking at propagation around urban structures. The third experiment in the series involved propagation around a small collection of urban structures. As part of this experiment, a series of triangular arrays was scattered around the area to examine the effect of urban structures on the line-of-bearing calculation. This presentation will present the results of these measurements and discuss the observed effects and their causes.
Acoustic and direct vibratory excitation, propagation, and scattering of Rayleigh waves at an air-ground interface.
Authors: Muir Thomas G. , Costley R. Daniel , Hickey Craig J. , Sabatier James M.
Published: March 2010

Finite element methods are utilized to model loudspeaker as well as shaker generation of sound, shear, and interface waves in an elastic solid containing an imbedded elastic scatterer. Results for steady state (continuous) and transient (pulsed) insonification, animated in the time domain, are presented to illustrate excitation, propagation, and scattering mechanisms and features. [Work supported by the U.S. Army Research Development and Engineering Command.]
Revisiting isodiachrons as a solution for localization.
Authors: Katlai Balaji , Vallarta Jonathan
Published: March 2010

Recently, there have been some new attemtps in source localization algorithms. In particular, Spiesberger et al. successfully introduced the notion of isodiachrons to localize a source. In this abstract, it is shown that the concept and notion of using an isodiachron can be understood in terms of mapping an unbounded trajectory (as in conventional hyperbolic fixing for localization) into a more closed form bounded surface. This is made possible by realizing a simple analytical continuation of the parameters in the algorithm. The resulting system is a bounded surface with isodiachrons as a solution. A simple proof-of-concept example is also demonstrated. This is a complementary solution/approach to the original idea of isodiachrons as proposed by Spiesberger. Additionally, other alternative approaches to translate (an unbounded) hyperbolic fixing technique to a source on a bounded surface are also discussed.
Optimal selection of weights for the linear total least-squares solution to impulsive source localization.
Authors: Frazier Wm. Garth , Rice Heath
Published: March 2010

At a recent ASA meeting, Monte Carlo-based noise performance analysis of several formulations and solution algorithms for the time-of-arrival (TOA) based impulsive source localization problem were presented. That analysis included two algorithms for parameter estimation using the (exact) linear formulation for the localization problem. Those algorithms were standard linear least-squares (LLS) and linear total least-squares (TLS). Using systematically derived, but in no way optimized, choice of weights, the TLS algorithm clearly demonstrated the ability to overcome the bias associated with LLS under conditions associated with low signal-to-noise ratio. Unfortunately, the bias reduction was obtained at a cost of high variance as compared to solutions associated with nonlinear formulations. This presentation presents results from investigations into performance of optimally chosen (variance reducing) weighting schemes for TLS and compares them to the performance of nonlinear formulations.
Error analysis of locating arbitrary sound sources in three dimensional space in real time.
Authors: Zhu Na , Wu Sean F.
Published: March 2010

This paper presents an error analysis in locating multiple incoherent sound sources in three dimensional space in real time by using a newly developed hybrid approach. The underlying principle of this hybrid approach consists of modeling of sound radiation from point sources in a free field, triangulation, and signal processing techniques. The impacts of target source locations and signal to noise ratio on the results are examined. Experimental results show that errors in source localization consist of primarily two components: biased and random errors. The former seems to be caused by the fact that the formulations used in acoustic modeling are for a free field, whereas the measurement environment is a non-free field. The latter is mainly caused by fluctuations in the source levels. To account for these errors, empirical formulations are developed and validated again in experiments with different settings. Results demonstrate that these empirical formulations can significantly improve the accuracy and spatial resolution of source localizations.
Coherence of low-frequency acoustic signals across a tetrahedral array.
Authors: Goldman Geoffrey, H
Published: March 2010

Many direction finding algorithms for acoustic applications require that the data collected at each microphone is coherent with respect to the data collected with another microphone in some frame. As the microphones are moved farther apart, the angular resolving power of the array is increased, but the coherence of the data is reduced. These factors are critical for designing the spatial configuration of acoustic arrays. The coherence of low-frequency acoustic signals was examined across tetrahedral microphone arrays elevated 1 m above the ground. The signal source was a UH-1 helicopter, which had strong harmonics between 10 and 100 Hz. The coherence was measured by tracking the harmonics of the signal, bandpass filtering each harmonic, cross correlating the filtered signals across all the microphone combinations, finding the maximum output, and then normalizing. The results indicate that the elevated microphone was less coherent than the non-elevated microphones. Multipath was determined to be a major factor affecting the coherency.
Noise cross-correlation and passive measurements of the sound speed profile in deep water.
Authors: Godin Oleg A. , Zabotin Nikolay A. , Goncharov Valery V.
Published: March 2010

Ambient acoustic noise in the ocean contains extensive information about its sources and the propagation environment. Successful application of the noise observations to acoustic characterization of the environment depends on identifying the noise properties which can be reliably measured and are sensitive to variations in temperature and other physical parameters of the ocean. This paper focuses on two-point noise cross-correlation and the environmental information that can be retrieved from it without any a priori knowledge about properties and locations of the noise sources. A technique to retrieve deterministic acoustic travel times from cross-correlations of noise recorded on two vertical line arrays is described. Feasibility of environmental monitoring with ambient noise is illustrated by results of passive tomography of the water column using noise recordings of opportunity, which were obtained in the North Pacific Ocean as a by-product of a long-range sound propagation experiment. Conflicting requirements on the hydrophone separation and frequency band are analyzed that originate from the demands to improve the inversion accuracy and to decrease noise averaging time. Remaining challenges in retrieving oceanographically meaningful results from acoustic noise cross-correlations are discussed. [Work supported by ONR.]
Long-time trends in low-frequency traffic noise for four sites off the North American west coast.
Authors: Andrew Rex K. , Howe Bruce M. , Mercer James A.
Published: March 2010

Measurements from four cabled-to-shore hydrophone systems located off the North American west coast permit extensive comparisons between “contemporary” low-frequency traffic noise (25–50 Hz) collected in the past decade to measurements made in the mid-1960s with the same in-water equipment at the same sites. An increase of roughly 10 dB over the band 25–40 Hz at one site has already been reported [Andrew et al., ARLO Acoust. Res. Let. Online 3 (2002)]. Newly corrected data from the remaining three systems corroborate this increase. Simple linear trend lines of the contemporary traffic noise (duration 6–12+ years) show that the current levels either hold steady or decrease at three of the four sites. These results confirm the Ross prediction, at least at these sites, that the rate of increase in traffic noise would be far less at the end of the last century compared to that observed in the 1950s and 1960s.
Three-dimensional sound propagation over submarine canyons.
Authors: Lin Ying-Tsong , Duda Timothy F. , Collis Jon M. , Lynch James F. , Newhall Arthur E.
Published: March 2010

Submarine canyons are common features of continental shelf and slope regions, e.g., Hudson Canyon in the Mid-Atlantic Bight. In this paper, the impact of submarine canyons on low-frequency sound propagation is studied using a three dimensional (3-D) parabolic approximation numerical program, which is implemented in a Cartesian coordinate system and utilizes the split-step Fourier technique and a 3-D variant of the Thomson and Chapman wide-angle approximation. This program will be first benchmarked with a classic wedge problem, and then used to study an idealized canyon environment to understand distinct 3-D sound propagation effects. The idealized environment has a Gaussian shaped canyon incising a slope. Horizontal focusing of sound in the canyon and energy flow into the canyon from an off-axis sound source are observed. A realistic model using the Hudson Canyon bathymetry shows even more complex sound propagation situations. Propagation conditions over different seabed types are also compared, and the 3-D field sensitivity to bottom properties is investigated. [Work supported by the Office of Naval Research.]
Impact of surface gravity waves on high-frequency acoustic propagation in shallow water.
Authors: Karjadi Entin A. , Badiey Mohsen , Kirby James T.
Published: March 2010

Sea surface roughness is one of several factors that significantly influences high-frequency (1–50-kHz) acoustic wave propagation in shallow water. The evolving sea surface introduces several variability effects including Doppler shift. Data analyses from high-frequency acoustic experiments show high-correlation between time, angle, and intensity fluctuations of received signals and varying sea surface conditions. In order to assess detailed acoustic signal interactions with the sea surface, a realistic wave model is developed and combined with an acoustic ray-based model. Model validity is evaluated by comparing the results with data from multiple experiments. [Work supported by ONR 321OA.]
Acoustic observations of subsurface instability.
Authors: Eickmeier Justin M. , Badiey Mohsen , Yamamoto Tokuo
Published: March 2010

A high-frequency (0.6–18-kHz), shallow water acoustic experiment (HFA2000) was conducted in Delaware Bay (15-m depth) during December 2000. Reciprocal transmissions of chirp signals (0.345-s duration) were radiated between three bottom mounted source-receiver tripod stations separated by 70–353 m. Environmental data were collected at a nearby oceanographic platform; simultaneously, a shipboard ADCP and CTD were deployed. Analysis of direct path station-to-station arrival times (between December 18th 00:00 and December 19th 10:00, during which 126 acoustic transmissions consisting of 29 chirps were radiated) revealed significant deviation from arrival time patterns established during previous tidal cycles. Examination of the corresponding signal intensity reflected this deviation. Independent ADCP data displayed current profile distortion during the period along the direction of the dominant flow channel. The mean slope of a wave number vs geo-time spectrum was calculated from each geo-time’s respective chirp series. Slope changes correlate to variations in the total signal intensity’s constituents, Itot(t) = 〈|E(t)|2〉, particularly the incoherent or scattered intensity, Iincoh(t) − Itotal(t) − Icoh(t). Through comparison with a Kolmogorov power spectrum and calculation of the corresponding Richardson number, a profile of environmentally induced subsurface instability has been developed.
Basics of blast physics.
Authors: Ritzel David
Published: March 2010

Blast science concerns the processes by which the energy of an explosion source becomes propagated into its surrounding environment, then interacts, loads, and damages materials, structures, and systems. Although explosive events have been chronicled for over 2000 yrs, and good empirical insights regarding blast phenomenology were established prior to WW-II, the advent of the nuclear bomb drove the first rigorous and concerted efforts to understand the detailed physics of blast propagation. Blast science merges with classical acoustic sciences in its far-field limits including phenomena such as atmospheric focusing. However, in the interaction of blast with composite structures including the human body, a wide range of transmitted, coupled, or overdriven mechanical waves of many types can be generated. There has been a significant resurgence of R&D in protective technologies against modern blast threats such as terrorist bombings and IED attacks against our armed services. The current paper presents a review of the basic of blast physics from the near to far fields, principles of blast simulation in the laboratory, as well as recent progress in the understanding of blast induced traumatic brain injury.
Effects of low blast levels on the central nervous system.
Authors: Säljö Annette , Svensson Berndt , Mayorga Maria , Bolouri Hayde , Hamberger Anders
Published: March 2010

Anaesthetized swine in crew positions were exposed to weapons in air or to explosives underwater. Blast parameters were correlated with those in the brain. The peak pressure in the brain (Pmax brain/air) was 0.7 for a bazooka (45 kPa), 0.5 for a howitzer (10 kPa), and 0.4 for a rifle (23 kPa). The brain/water Pmax for the detonation pulse of under water explosives was only 0.1, but 0.3–0.4 for the secondary pulses. The results indicate that low-frequency spectra penetrate easier into the brain. Histological examination revealed small hemorrhages in rear regions of the brain. In rats, we investigated the effect of shock tube blasts. After exposure to 10 or 30 kPa, cognitive performance (Morris Water Maze) decreased by 50%. The intracranial pressure (ICP) increased in a dose dependent fashion to reach peak levels 6 h after exposure at 10 kPa and 10 h after exposure to 30 or 60 kPa. An initial ICP elevation took place 30 min after exposure to 60 kPa, and 2 and 6 h after exposure to 30 and 10 kPa, respectively. A prophylaxis, consisting of a 2 week intake of hydrothermally fermented cereals, reduced significantly the blast effect both on ICP and cognitive performance. [The authors thanks Svante Hjer, Samba Sensors AB. The study was supported by the Swedish Armed Forces and FMV.]
Effects of a simulated blast pulse train on a simple neural model.
Authors: Wahab Radia , Liu Yunbo , Krauthamer Victor , McCabe Joseph , Moratz Chantal , Egan Ryan , Zderic Vesna , Myers Matthew
Published: March 2010

In the treatment of traumatic brain injury (TBI) due to blast-wave exposure, an understanding of the mechanisms of injury is critical for proper intervention. One mechanism of particular importance is the interaction of blast waves with neurons. In order to investigate this interaction in isolation from other TBI mechanisms, blast waves were simulated on a local (approximately 1-mm) scale using high-intensity focused ultrasound (HIFU). The acoustic impulse of the HIFU blast wave was selected to approximate the impulse of an actual blast. As a first step in a chain of increasingly complex neural models, the giant axon in an earthworm was used in this study. Intact earthworms were exposed to simulated blast waves from an HIFU transducer, and axonal action potentials were stimulated and recorded. The action potential amplitude decreased continuously with increasing impulse, with the signal typically vanishing at about 8000 Pa s. The conduction velocity showed more of a threshold effect, decreasing minimally from control values until an impulse of about 4000 Pa s was reached, at which point the decline was more rapid. Results indicate that exposing isolated neurons to HIFU-simulated blasts is a promising approach for studying TBI.
Toward the non-invasive determination of cerebral perfusion pressure.
Authors: Mourad Pierre D.
Published: March 2010

Brains subjected to blast from an explosive or other sources of trauma often develop intracranial hemorrhage or edema or loose their ability to autoregulate the blood flowing into the brain (cerebral autoregulation). Such damage can, in turn, lead to increases in intracranial pressure (ICP) and decreases in cerebral perfusion pressure (CPP=arterial blood pressure—ICP) that, in turn, can lead to ischemia and/or herniation, and brain death. This is not good for the patient. To assay ICP, of intrinsic value, and CPP—two variables of critical interest to the medical staff who treat and manage patients with head injury—requires a (invasive) neurosurgical procedure. Here I describe research performed over the last several years whose target is the prediction of ICP and CPP using arterial blood pressure data as well as data derived from transcranial Doppler. In particular, I will review the process by which we collected sufficient human-derived data in order to make a decent pass at predicting ICP for patients with closed traumatic brain injury (TBI) and a great effort at predicting CPP for these and a complementary group of patients.
Blast-induced traumatic brain injury research at Lawrence Livermore National Laboratory.
Authors: Moss William C. , King Michael J.
Published: March 2010

Our blast-induced TBI research has computational and experimental components. Our numerical hydro-structural simulations show that non-lethal blasts can induce sufficient flexure of the skull to generate potentially damaging loads in the brain, even if no impact occurs. The possibility that this mechanism may contribute to TBI has implications for the diagnosis of soldiers and the design of protective equipment such as helmets. Our experimental work involves designing and testing blast dosimeters, which are needed to quantify the blast environment around the soldier, independent of the mechanism(s) causing TBI. One system that uses MEMS sensors incorporated into the helmet and suspension would record peak pressure, positive-phase duration, blast direction, loads directly on the skull, and accelerations. Another system uses less sophisticated, inexpensive, small, lightweight, disposable, unpowered sensors that act as “yes-no” gauges that indicate the blast magnitude by visual inspection of the gauge. This system is a trade-off between quantity and quality of data, which may be viable, based on current DoD needs. [This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.]
Numerical simulation of mechanisms of blast-induced traumatic brain injury.
Authors: Teland Jan Arild , Arrhén Fredrik , Hamberger Anders , Huseby Morten , Rahimi Reza , Säljö Annette , Svinsås Eirik
Published: March 2010

Blast-induced traumatic brain injury caused by road bombs has lately become a larger part of allied injuries. The same mechanisms may also be responsible for milder injuries of similar nature, resulting from training with large caliber weapons and explosives. In this paper, the blast effects from a weapon on the brain are investigated. Using the hydrocode AUTODYN, numerical simulations of shock wave propagation into the brain are performed. The shock wave is calculated from a complete numerical simulation of the weapon, including the burning gun powder gas inside the barrel, acceleration of the projectile, and the rapid gas flow out of the muzzle. An idealized head is placed in the simulation at the position of personnel firing the weapon. Here we focus on the qualitative mechanisms of the propagation of the shock wave through the skull and into the brain. The results are compared with experiments carried out on anesthetized animals. To simulate real training scenarios, pigs were placed in position of personnel and exposed to impulse noise generated from weapons. Blast parameters in the air were correlated with those in the brain.
Influence of skull microstructure on blast-induced pressures in the brain.
Authors: Turner Joseph A. , Liu Jinjin
Published: March 2010

The interaction of blast waves with the human head is complicated by many factors including the geometry, material nonlinearities, and skull microstructure. In particular, the flat bones of the skull are comprised of the outer and inner tables (cortical bone) and the diploë (trabecular bone) on the interior. This microstructure results in both scattering and absorption of incident pressure waves. A clear understanding of these effects is needed if pressure profiles within the brain are to be accurately modeled. The focus of this presentation is on finite element wave simulations that have been developed to account for this complex organization. The models are first used to examine the scattering attenuation and coherency loss resulting from the microstructure as a function of incidence angle and frequency for plane wave incident pressure profiles. These models are then extended to more realistic pressure profiles representative of blast waves. The statistics of the microstructure are shown to play a key role in the peak pressures observed within the skull. It is anticipated that this work will lead to a better understanding of role of skull microstructure on blast-induced traumatic brain injury. [Work supported by ARO.]
A finite element approach towards understanding violin structural modes.
Authors: Gough Colin
Published: March 2010

A COMSOL finite element package has been used to model the structural modes of vibration of the violin treated as a shell structure with orthotropic arched plates. Such computations enable the physical properties of the plates, ribs, and soundpost to be varied over many orders of magnitude. This provides major insight into the nature of the coupling of the top and back plates by the ribs and the role of the soundpost in coupling the radiating “breathing” modes of the violin to the weakly radiating anti-symmetric modes excited by the bowed string induced rocking of the bridge on the central island area. Examples will be shown of the influence of such factors as plate thickness/density, anisotropy, arching, rib strength, and position of soundpost on the frequencies and excited strengths of the strongly radiating “signature” modes below 1 kHz. In addition to determining the mode shapes and frequencies of the excited modes, their contributions to the radiated sound are also computed. Comaparison will be made with experimentally observed mode shapes and frequencies.
Global modeling of the violin radiativity profile.
Authors: Bissinger George
Published: March 2010

The violin’s radiativity (pressure/force)profile maintains a consistent shape across quality classes, arguing for a quality-independent generalized global model. In the 196–660 Hz region the lowest cavity modes A0 and A1 and the two first corpus bending modes B1 generate almost all the radiativity, with the B1 modes treated as “pumps” for A0 and A1. The B1 modes have nodal patterns similar to the plate bending (primarily) modes 2 and 5, suggesting a link to the violin’s critical frequency. The essentially serial character of the violin’s sound chain leads naturally to a simplified expression for the averaged-over-sphere radiativity profile as a product of just two filters: (1) string-to-corpus through the tuned bridge substructure “gatekeeper”) filter and (2) the “egress” filter for the vibration-radiation transformation, the latter reliably parametrized by the radiation-total damping ratio FRAD. FRAD incorporates the violin critical frequency as well as top and back plate properties in a generalized form. The gatekeeper filter on the other hand is considerably more complex; present bridge models must be augmented by systematic empirical measurements to understand the effects of varying bridge rocking mode frequency or “wing” mass. Recent three-dimensional vibration measurements provide additional insight into bridge-corpus impedance effects.
Development of the Titian Stradivari finite element model.
Authors: Pyrkosz Michael A. , Van Karsen Charles D. , Bissinger George
Published: March 2010

As part of the continuing effort to understand the structural and acoustic behavior of one of Stradivari’s masterpieces, a finite element (FE) model of the Titian Stradivari (1715) has been constructed from computed tomography (CT) scans. The CT data were used to extract high-fidelity geometry and density information specific to this violin. This violin is unique in that it is the only one of Stradivari’s instruments that has been measured with a full three-dimensional mobility scan over the top and back plates and ribs as well as acoustic radiativity over a sphere. Hence this solid model can be updated and correlated with this comprehensive experimental data set. The current status of this solid modeling effort will be reviewed in the presentation.
The violin as a statistical energy analysis network.
Authors: Davis Evan B.
Published: March 2010

This paper applies elementary statistical energy analysis (SEA) concepts to the violin. Modern makers have been experimenting with ultra-light violins trying to solve the problem increasing the overall output while maintaining the spectral balance of the classical violin. Anecdotal experimental evidence suggests the traditional bridge is not “appropriate” for the ultra-light violins. The ultra-light design problem is used as a case study for hybrid-SEA model. SEA modeling applies a high-modal destiny, high-frequency, approach which complements the low-frequency, low-modal density, finite element approach. The focus of the SEA modeling is the top plate or belly of the violin addressing the interaction of the cross-arching, plate thickness, wood material properties, and the dynamics of the bridge. The cross-arch of the violin is seen as a critical design feature in the violin. The current approach is more properly a “hybrid method” where the belly and box volume are represented as SEA subsystems and the bridge is represented with a two mode subsystem. The hybrid-SEA analysis demonstrates that the ultra-light’s bridge mass must be in the same bridge-mass to belly-mass ratio as the traditional violin to maintain the spectral balance of the classical violin.
Noise and vibration phenomena in aircraft wheel and brake systems.
Authors: Rook Todd E.
Published: March 2010

There is a wide variety of noise and vibration phenomena in aircraft brake systems for which must be accounted in the design process of such systems. These phenomena include such modes as whirl and squeal, the latter of which can be quite different from its counterpart in automotive systems and has likewise received much less attention in the literature than its automotive counterpart. Consequently, an overview of such phenomena with representative results from simulations and experiments will be presented to highlight the differences. Complicating matters is that brake-induced vibration often involves strong coupling with the aircraft structure, thereby necessitating a system level understanding beyond the brake itself. This aspect poses a particular problem to a brake component supplier in how to ensure favorable noise and vibration behavior for the full aircraft system, particularly early in the development cycle. To accomplish this goal, Goodrich has developed a successful methodology combining simulation and testing to assess the noise and vibration behavior at an earlier stage. The methodology implements simulations to guide appropriate brake component tests that are more tractable for the brake supplier yet sufficiently mimic the full system environment. With the combined simulation and testing, a reduction in actual testing can be achieved while improving component noise and vibration performance.
Enhancing accuracy in reconstruction of vibro-acoustic responses of a complex structure using Helmholtz equation least squares based nearfield acoustical holography.
Authors: Natarajan Logesh Kumar , Wu Sean F.
Published: March 2010

In traditional nearfield acoustical holography, the acoustic pressures in the near field are measured, and the entire acoustic field including the normal component of the surface velocity are reconstructed. This type of approach may be appropriate for reconstructing the acoustic pressure field, but not for reconstructing normal surface velocity in practice because not enough nearfield information is collected to yield satisfactory reconstruction of the normal surface velocity. In this paper, we propose to supplement the acoustic pressure measurements with a few normal surface velocity measurements, which can be used as benchmarks in optimizing the reconstruction of normal surface velocity. These data are taken as input to the Helmholtz equation least squares method based NAH to reconstruct the acoustic pressure and normal velocity on the surface of a vibrating structure. The accuracy in reconstruction is examined experimentally on a baffled rectangular plate with clamped boundary conditions subject to random excitations. To validate the results, the reconstructed field acoustic pressures are compared with those measured by microphones, and the normal surface velocities were compared with the benchmark values collected by using a scanning laser vibrometer under the same condition.