bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic color of viscoelastic objects in two-fluid environments: High-fidelity, high-speed, three-dimensional finite-element modeling.
Authors: Burnett David S.
Published: March 2010

NSWC PCD has developed a computer simulation system for modeling the acoustic color (target strength versus frequency and aspect angle) of realistic three dimensional (3-D) objects that are near to or straddling the interfaces between different fluids. It employs high-fidelity (fully 3-D physics throughout object and environment), finite-element (FE) modeling of acoustic scattering from viscoelastic objects. It is implemented in a scalable-architecture, multiblade rack system that automatically runs hundreds of thousands of FE models, changing the mesh resolution and outer fluid boundaries of the models as they sweep over frequency. This frequency-dependent modeling yields a frequency-independent modeling error for the acoustic color response. This, in turn, yields higher accuracy for subsequent signal processing of the acoustic color data. The first part of this paper will present a brief overview of the theoretical, numerical, and software issues. The second part will present verification and validation of the system: (1) ultra-high-precision correlation with T-matrix simulations for four canonical target/environment configurations and (2) experimental validation for objects in free space and straddling the interface between two different fluids. [Work supported by ONR and SERDP.]
Energy finite element analysis of naval vehicles.
Authors: Vlahopoulos Nickolas , Wu Kuangcheng
Published: March 2010

Simulation methods can be used for meeting both the new acoustics and vibration initiatives for surface ship silencing. An energy finite element analysis (EFEA) formulation has been developed for computing efficiently the vibration of complex structures and the associated radiated noise at frequencies beyond the limits of conventional finite element methods. The EFEA provides a very attractive alternative to the statistical energy analysis (SEA) because it uses the same finite element model which is utilized for other simulations (i.e., structural analysis), while the SEA requires the development of a completely new model based on a lumped parameter approach. Further, the SEA requires estimates of modal densities for the various subsystems which introduce difficulties and approximations in the solution. Thus, the EFEA streamlines the structural-acoustic analysis within the ship design process due to modeling commonality with other disciplines. In this presentation, the main theoretical aspects of the EFEA will be presented first. Results presented for two 1/8th scale structures representing an advanced double hull design and a conventional hull design of a surface ship are analyzed. Results for the structural vibration induced on the outer bottom part of the structures are compared to available test data.
Numerical study of structural intensity for a model airframe structure in healthy and damaged states.
Authors: Shepherd Micah R. , Conlon Stephen C. , Semperlotti Fabio
Published: March 2010

Structural damage due to fatigue or material flaws presents a major challenge for many engineering applications. To address this challenge, structural health monitoring techniques have been developed in an effort to determine the type, severity, and location of the damage. Many of these techniques are based on the nonlinear contact phenomenon. In this paper, structural intensity methods are used as a damage-detection metric on a simplified airframe structure. A finite-element model was created and the structural intensity field was mapped over the surface using individual element power flow estimates. Damage was then introduced into the model by removing connectivity between elements and including nonlinear stress-strain relationships and contact at the damage location. Structural intensity maps were then compared to the healthy case to correlate the changes with the damage state. More specifically, the increase in structural intensity at the sub- and super-harmonics was found to be indicative of the damage state. The results of this numerical study show the potential of surface structural intensity in autonomous damage detection for flight vehicles. The implications of this type of damage detection metric with respect to damage size and location will also be discussed.
Effects of metrical structure on syllable timing II.
Authors: Tinius Megan , Fourakis Marios
Published: March 2010

Fourakis and Monahan [J. Linguist. (1988)] examined the effects of two different types of metrical foot (iamb and anapest) on syllable timing in 3 ft utterances. These utterances were comprised of three iambs, three anapests, and every possible combination of the two types. The present research follows the same paradigm but uses trochees and dactyls instead of iambs and anapests. A set of eight 3 ft long sentences was constructed. At one end there was the three trochee sentence: Auctions rescue business. At the other end was the three dactyl sentence: Auctions may rescue his businesses. The intermediate six sentences were formed by different combinations of the metrical feet. Five male and five female native speakers of Midwestern American English were recorded producing five repetitions of each sentence at a normal rate of speech. Segments were assigned syllable membership based on the maximum onset principle. Results will be presented on syllable durations as a function of foot type and sentence type. [Research supported by the University of Wisconsin Madison Graduate School.]
Mandarin and English initial stops produced by Mandarin-English bilinguals.
Authors: Liao Jia-Shiou
Published: March 2010

This study investigates the relationship between the way Mandarin-English bilinguals and native speakers of English pronounce English initial stop consonants, and between the way Mandarin-English bilinguals pronounce Mandarin and English stops, with respect to voice onset time. Twelve Mandarin subjects who had learned English as their second language and were studying at a US university were asked to read randomized lists of 72 Mandarin characters and of 72 English words; twelve English subjects read only the list of English words. The syllable structure of each Mandarin character and of each English word in this study was CV. The Mandarin consonants were initial aspirated and unaspirated /p, t, k/; the English consonants were initial /p, t, k/ and /b, d, g/. The vowels used in both lists were high vowels. Significant differences are found between the Mandarin-speaking subjects’ articulation of all the Mandarin stops and their minimally paired English equivalents produced by the English-speaking subjects. Significant differences are found between Mandarin and English speakers’ articulation of the same English stops, except for that of /t/. When comparing the Mandarin-speakers’ articulation of Mandarin stops and their minimally paired English counterparts, a significant difference is found only between English and Mandarin aspirated /p/.
Priming at the level of phonetic detail: Evidence from voice onset time (VOT).
Authors: Levi Susannah , Bruno Jennifer
Published: March 2010

Priming studies have shown effects on the production of target words when the target and prime are identical and when the target and prime share some but not all phonological features. Variation at the level of phonetic detail has also been found to affect production in word shadowing tasks where speakers produce longer VOTs when the VOT of the sample word is artificially lengthened. In this study, we examine the effect of naturally produced, yet systematic within-category variability in the VOT of the prime on the production of a target word for visually presented words. Primes either contained a voiceless stop with a long VOT (“keen”) or a short VOT (“pan”). The target words contained a voiceless alveolar stop followed by five vowels which varied in height and backness (e.g., “tune” and “ten”). Results showed that the same target word was produced with longer VOTs when the prime contained a naturally long VOT than when the prime contained a naturally short VOT. These results suggest that speakers are sensitive to natural within-category variability, and that this sensitivity affects production across different segments.
“Probably, OK, whatever!”: Variability in conversational speech stops and flaps.
Authors: Warner Natasha , Tucker Benjamin V.
Published: March 2010

In casual, conversational speech, speakers often do not fully realize all segments one would normally expect in a given word. For example, “better” may be pronounced with an approximant instead of a medial flap (if the tongue fails to make a complete closure at the alveolar ridge), the expected flap may be entirely deleted, or the segments may be so heavily overlapped that it is almost impossible to say which segments are present and which not. The current work investigates how much reduction occurs (including both changes and deletions), comparing casual conversations, connected reading, and isolated word-list reading. It compares the phonemes /p, t, k, b, d, g/, post-stress vs inter-unstressed, and six segmental environments. The results represent 13 native English speakers and comprise a dataset of more than 9000 tokens, with several acoustic measures. This provides very thorough data on phonetic variability in both natural and “lab” speech. The work finds relatively little effect of stress and complex effects of segmental environment attributable to places of articulation. It also provides insight into how variable speakers are in how much they reduce, both within a speaker and within the population, a topic not often addressed in phonetic research.
Dependency of compensatory strategies on the shape of the vocal tract during speech perturbed with an artificial palate.
Authors: Brunner Jana , Hoole Phil , Guenther Frank H. , Perkell Joseph S.
Published: March 2010

When adapting to an articulatory perturbation, different speakers may use different strategies. This study investigates the hypothesis that the choice of strategy depends on vocal tract shape. Vowel production was perturbed with prostheses that changed palatal shape. Three speakers had a prosthesis that effectively moved the alveolar ridge posteriorily; three others had a prosthesis that effectively flattened the palate. EMA recordings of speakers’ adaptive behavior showed that during the production of the vowel /y/, the speakers with the alveolar prosthesis compensated by using increased lip protrusion. The speakers with the flat prosthesis used about the same amount of lip protrusion as without perturbation. We hypothesize that this is because for the first group of speakers the main constriction in the vocal tract was moved forward due to the changed palatal outline: the front cavity became too short, which was compensated for by more lip protrusion. This hypothesis is being explored by determining whether the DIVA speech production model will produce compensations like the subjects when the model’s vocal tract is adapted to fit individual vocal tract shapes using detailed information about the subjects’ vocal tracts from MRI recordings. Complete results will be reported and discussed. [Work supported by DAAD, NIH.]
Modeling the acoustic channel for mixed pressure and particle velocity sensors.
Authors: Hursky Paul , Porter Michael B.
Published: March 2010

Looking at our repertoire of acoustic modeling techniques, ray tracing and Gaussian beams provide a good match to modeling the underwater channel for acoustic communications, given their fundamentally broadband nature. We will discuss how we have augmented existing acoustic models, including Gaussian beam and normal mode codes, to produce particle velocity predictions. In both of these cases, the modifications consisted of manipulating the components used to represent the pressure field, as opposed to relying upon a finite difference approximation of the predicted field itself. We will discuss further modifications to these codes that enable the dynamic features of the channel to be modeled, including source and receiver motion, and motion of the ocean surface due to ocean surface waves. It is important to model realizations of the channel, rather than averaged representations, because many of the high-speed, coherent modulation schemes that are the focus of continuing research use tracking loops in their design. These tracking loops must be stressed with realistically time-evolving channels. Acoustic channel predictions will be compared with experiment data from acoustic communications experiments off the coast of Kauai in Hawaii.
Geo-acoustic inversion with vector sensors in shallow water.
Authors: Li Fenghua , Zhang Renhe
Published: March 2010

Vector sensors have attracted much attention in recent years. However, relative few papers have been published on the geo-acoustic inversion with vector sensors. The data recorded with vector sensors in several shallow water acoustic experiments have been studied in this paper. The experimental data and theoretical analyses indicate that (1) the intensity of the vertical particle velocity decreases faster than that of the horizontal particle velocity; (2) the same normal modes of the horizontal particle velocity and the vertical particle velocity have similar transmission losses, but different amplitudes and phases; (3) the difference of the mode amplitudes between the horizontal particle velocity and the vertical particle velocity is dependent on the eigen-value and receiver depth. With those properties, two geo-acoustic inversion schemes employing vector sensors have been developed. The first inversion scheme uses a combination of matched field processing and the difference of transmission losses between pressure and particle velocity. The second estimates the bottom sound speed and attenuation from the amplitudes of normal modes of particle velocities. Experimental results show that the developed geo-acoustic inversion methods with vector sensors can decrease the uncertainty of inversion in comparison with that by hydrophones.
Amplitude, phase, location, and orientation calibration of an acoustic vector sensor array, Part I: Theory.
Authors: de Bree Hans-Elias
Published: March 2010

An acoustic vector sensor array consists of multiple sound pressure microphones and particle velocity sensors. A pressure microphone usually has an omni-directional response, yet a particle velocity sensor is directional. Currently, acoustic vector sensor arrays are under investigation for far field source localization and visualization. One of the major practical issues in these applications, however, is to determine the accurate position, orientation, and complex (phase and amplitude) sensitivity of each sensor within the array. In this study, a calibration method is developed to determine each of those crucial parameters based on a limited number of measurements with a reference sensor and multiple sound sources located at known locations. The calibration method is also designed to be robust to mistakenly switched cable connections. Ideally, the calibration process should take place in an anechoic environment, but efforts have been made to compensate the effects of moderate background noise and reflections.
Proof of principle for geo-acoustic inversion of vector sensor array data.
Authors: Koch Robert A.
Published: March 2010

Acoustic data collected from an array with elements comprised of omni-directional hydrophone sensors co-located with acceleration vector sensor triplets are analyzed for seabed geo-acoustic information. The data were collected during the passage of a surface vessel, the R/V Montague, in an August 2006 experiment conducted in Monterey Bay. Geo-acoustic inversion with the vector sensor acceleration components parallel to the array line of bearing produced a solution approximately identical to the solution obtained from the inversion of the hydrophone array data. [Sponsored by ONR.]
The rest of the school: An investigation into good acoustical design of non-classroom spaces in primary and secondary schools.
Authors: Markham Benjamin , Hinckley Jennifer
Published: March 2010

The focus on acoustics in recent standards and guidelines such as the ANSI Standard S12.60, the Leadership in Energy and Environmental Design (LEED) for Schools system, and the Collaborative for High Performance Schools (CHPS) has rightly been on classrooms. Each of them does address other school environments also, although sometimes without particular specificity. After reviewing relevant American standards and guidelines for gymnasiums, libraries, lobbies, corridors, auditoriums, and other spaces that do not fit neatly into the classroom designation, this paper addresses good practices in the acoustical design of such critical environments through the use of a series of case studies. Specifically, the authors suggest room acoustics design parameters and appropriate background noise and sound isolation criteria for non-classroom spaces in primary and secondary schools.
Acoustical compromises: Working with a design team for maximum isolation at minimal costs in high school music facilities.
Authors: Harght Pamela J.
Published: March 2010

Texas Public High Schools place a large emphasis on their music and drama programs, often providing facilities for their students that are far superior than many 4-year college and universities. These high school facilities include several rehearsal rooms for band, choir, orchestra, percussion, ensembles, mariachi and individual practice. In addition, they also often have a drama classroom, a black box theater, and a Performing Arts Center. When working with the design team on these projects, there are often many obstacles to work around in order to provide the best scenario possible for the end user. These “obstacles” often include (but are not limited to) school district codes, budgets, the “convenience” factor, city codes, and space planning. This paper will showcase many high school music facilities through the south and southeast and the compromises and obstacles that were overcome with the end result goal as satisfying the music department.
Helping clients realize superior room acoustics while achieving other facility goals.
Authors: Farion Rob
Published: March 2010

Addressing the needs of a space often involves considering many competing objectives. When room acoustic performance is one of the priorities, there is potential to address other priorities in conjunction with acoustic considerations. Integrating interior design goals with acoustic requirements often allows more resources to ultimately be available for acoustic considerations. This presentation outlines two educational facility projects where clients were assisted in meeting their goals by incorporating interior design objectives and room furnishings with acoustic performance outcomes.
The evolution of the gymatorium and cafetorium in primary schools.
Authors: Doggett Felicia
Published: March 2010

Many primary schools do not have formal auditoriums, but the school still needs a space for performances and assemblies. The existence of “gymatoriums” and “cafetoriums” in these schools is essential to the student body and staff. Far from being just a gymnasium or cafeteria with a stage at one end, these rooms are fully functioning performance spaces with appropriate acoustics and audio systems. What many in the school may deem most important, however, is that they still function very well for their everyday uses of gymnasiums or cafeterias. This presentation explores several gymatoriums and cafetoriums and their acoustical and audio design elements.
A comparison of biosonar beampatterns in bats.
Authors: Müller Rolf , Yan Zhen
Published: March 2010

The beampattern associated with a diffracting baffle around a sound receiver can be predicted efficiently using numerical methods. Here, such methods have been used to derive estimates for a large number of reception beampatterns from high-resolution digital models of the shapes of pinnae (outer ears) of different bat species. For each ear, beampatterns were obtained with a high-directional resolution (1 deg) and for a set of frequencies that sample the frequency band used by the respective species adequately. This allows the characterization of frequency-dependent features of the beampattern such as the number of lobes present, as well as their size, shape, orientation, and position. The resulting data set allows comparisons between different ecological groups, such as the continuous frequency (cf-fm) and frequency modulated bats (fm-bats) as well as an assessment of variability within such species groups. Comparisons across a larger number of species have facilitated the identification of outliers, i.e., species with unique beampatterns. Such unique beampattern features may be related to unique uses of the animals biosonar system or unique constraints under which these tasks have to be accomplished. Tentative links to unique features of the pinna geometry have also been established.
A digital model for the deformation of bat ears.
Authors: Balakrishnan Sreenath , Gao Li , He Weikai , Müller Rolf
Published: March 2010

In bats, the directivity patterns of the biosonar system are shaped by the surface geometry of the pinnae. Since many bat species are capable of large ear deformations, these beampatterns can be time-variant. To investigate this time-variance using numerical methods, a digital model that is capable of representing the pinna geometry during the entire deformation cycle has been developed. Due to large deformations and occlusions, some of the surfaces relevant to sound diffraction may not be visible and hence the geometry of the entire pinna has to be computed from limited data. This has been achieved by combining a complete digital model of the pinna in one position with time-variant sparse sets of three dimensional landmark data. The landmark positions were estimated using stereo vision methods. A finite element model based on elasticity was constructed from CT scans of the pinna post mortem. This elastic model was deformed to provide a good fit to the positions of the landmarks and retain values of smoothness and surface energy comparable to life. This model was able to handle ratios of data to degrees of freedom around 1:5000 and still effect life-like deformations with an acceptable goodness of fit.
Reanalyzing auditory sensitivity: The functional audiogram as modeled by the bat detecting moth ear.
Authors: Jackson Matthew E. , Asi Navdeep , Fullard James H.
Published: March 2010

Auditory sensitivity has often been measured by identifying neural threshold in real time (online) which can introduce bias in the audiograms that are produced. This was tested by recording auditory nerve activity of the Notodontid moth Nadata gibbosa elicited by bat-like ultrasound and analyzing the response offline. The offline audiogram was compared to a published online audiogram showing that the bias introduced can result in a difference in both the best frequency of this moth ear and the audiogram shape. The offline neural threshold audiogram was then compared to audiograms produced using behavioral threshold definitions based on (1) spike period and (2) the latency to first spike, showing that audiograms produced using these theoretical behavioral definitions to have a similar shape. Finally, predictions on the distance at which Notodontid moths may evade bats using negative phonotaxis or the acoustic startle response are made, using the number of spikes elicited as a proxy for distance.
Direct measurements of subjective loudness in a bottlenose dolphin.
Authors: Schlundt Carolyn E. , Finneran James J.
Published: March 2010

Equal-loudness contours were measured in a bottlenose dolphin (it Tursiops truncatus) trained to perform a loudness comparison task. The subject was presented two sequential tones and whistled if the first tone was louder, and produced a burst pulse or “buzzed” if the second tone was louder. Approximately 70% of trials were “known” comparisons [e.g., tones of same frequency but different sound pressure levels (SPLs)] and allowed performance to be tracked within sessions. The remaining comparisons were probe trials, consisting of a 10-kHz standard tone with a fixed SPL (either 90, 105, or 115 dB re 1 μPa) and a comparison tone, whose frequency was fixed but whose SPL varied. Presentation order of probe trials was balanced. Eleven comparison frequencies ranged from 3.5 to 113.1 kHz. Logistic regression was used to derive curves relating the probability of the comparison tone being perceived louder. The 50% point represented the SPL at which the comparison and standard tones were equally loud. The data represent the first direct measurement of equal-loudness curves in any animal and show the relationship between the frequency and subjective loudness. Loudness contours may be more appropriate for assessing behavioral effects of sound, assuming behavioral reactions are more strongly related to loudness than SPL.
Numerical modeling techniques common to medical ultrasound and detection of undersea objects.
Authors: Burnett David S.
Published: March 2010

Acoustic scattering from gallstones, diseased tissues, and objects on the ocean floor and submarines are all governed by the same underlying partial differential equations describing wave propagation in fluids and viscoelastic solids. These objects differ in size by many orders of magnitude. However, they are all the same “acoustic size” when each is insonified at a frequency such that the ratio of object-diameter-to-wavelength is the same for all. Objects of the same acoustic size have two important characteristics: (1) they exhibit qualitatively similar physical-acoustic phenomenology and (2) numerical modeling consumes similar computational resources. Given these observations, many of the numerical modeling techniques developed by the U.S. Navy for acoustic scattering from undersea objects may be applicable to biomedical ultrasound applications. This paper explores these possibilities. NSWC PCD has developed a computer simulation system for modeling the acoustic color (target strength versus frequency and aspect angle) of realistic objects. It automatically runs hundreds of thousands of three dimensional FE models, changing the mesh and finite fluid boundaries of the models as they sweep over frequency and yielding uniform accuracy with frequency. This paper will present an overview of the technology and numerical verification and validation of the system. [Work supported by ONR and SERDP.]
Acoustic streaming for direct delivery of therapeutics into tissue.
Authors: Raghavan Raghu
Published: March 2010

Ultrasound has been used in medical drug delivery but largely for altering membrane permeability. We are investigating acoustic streaming for delivery of therapeutics, such as drug molecules or other particulates, into brain tissue, with other applications for the future. Acoustic streaming potentially can enhance fluid and particle flux in interstitial pathways in tissue. The conventional equations that describe streaming in fluids are not directly applicable to porous media such as the brain. In this study, a modified Biot equation is employed to develop a theoretical framework to account for the attenuation mechanisms dominant in acoustic streaming in porous media. The analytical solutions obtained for isotropic, homogeneous media are presented and compared with experiments conducted on gel phantoms, and with results reported for streaming in live monkey brains. The dependence of streaming-induced therapeutic transport on acoustic parameters and tissue properties are investigated. The theoretical framework was used to determine optimal operating parameters of ultrasonic devices for streaming-based drug transport in porous tissue with particular emphasis on two objectives: (1) reduction in backflow from catheters inserted into brain tissue for direct delivery and (2) delivering drugs into the margins of a resection cavity following surgery for brain tumor.
A generalized formulation for scattering from arbitrary distributions of homogeneous cylinders or spheres.
Authors: Hesford Andrew J. , Astheimer Jeffrey P. , Waag Robert C.
Published: March 2010

A generalized form of spatial harmonic expansion suitable for calculation of scattering by arbitrary distributions of homogeneous cylinders in two dimensions and homogeneous spheres in three dimensions is presented. The method is applicable for general incident fields expressed as angular spectra of plane waves. The technique uses harmonic expansions, physical acoustic boundary conditions, and mode matching to represent scattering by each individual object as a diagonal operator. Interaction between objects is treated with a T-matrix approach in which scattering from one object is applied to another using translation operators that shift the origins of harmonic expansions between scatterers. The generalized form permits efficient calculations in both two and three dimensions. These calculations are used to assess the validity of two-dimensional approximations to three-dimensional scattering for volumes containing multiple interacting spheres that are illuminated by elevation-focused beams. Differences in the two-dimensional and three-dimensional results are attributed to out-of-plane scattering and partial-volume effects caused by significant variations in the scatterer cross section over the elevation width of the focused beam.
Characterization of clutter in ultrasonic imaging using a nonlinear full-wave simulation method and in vivo human tissue.
Authors: Dahl Jeremy J. , Pinton Gianmarco F.
Published: March 2010

Clutter is a well known image degradation mechanism in ultrasonic imaging that is patient dependent. Despite widespread agreement on clutter sources, there are few studies on sources and their contribution to overall image clutter. We have performed simulations of clutter using a nonlinear, full-wave method to demonstrate the characteristics and sources of ultrasonic clutter. Representations of human abdominal layers, created from histological stains of human abdominal layers, were placed at the surface of the transducer. Point targets and anechoic cysts were simulated to demonstrate the characteristics of clutter resulting from these near-field layers. We have also performed matching in vivo experimental studies in human bladders and livers. The simulations and experiments show consistent results. Clutter resulting from near-field tissue layers is spatially coherent with respect to axial motion and incoherent in the sampled pressure field. The contribution of off-axis clutter resulting from the tails of the point-spread-function is shown to be relatively small (<5%) compared to the contribution of clutter associated with near-field layers (approximately 68%). Thus, the dominating source of clutter is associated with multiple reflections in near-field tissue layers. Clutter due to off-axis scattering dominates only when an interfering target is close to the imaging target. [This work is supported by the NIH Grant R21-EB008481 from the NIBIB. Technical support was provided by the Ultrasound Division at Siemens Medical Solutions USA, Inc.]
Modeling nonlinear acoustic waves in media with inhomogeneities in the coefficient of nonlinearity.
Authors: Demi L. , Verweij M. D. , van Dongen K. W. A.
Published: March 2010

The refraction and scattering of nonlinear acoustic waves play an important role in the realistic application of medical ultrasound. One cause of these effects is the tissue dependence of the nonlinear medium behavior. A method that is able to model those effects is essential for the design of transducers for novel ultrasound modalities. Starting from the Westervelt equation, nonlinear pressure wave fields can be modeled via a contrast source formulation, as has been done with the INCS method. An extension of this method will be presented that can handle inhomogeneities in the coefficient of nonlinearity. The contrast source formulation results in an integral equation, which is solved iteratively using a Neumann scheme. The convergence of this scheme has been investigated for relevant media (e.g., blood, brain, and liver). Further, as an example, the method has been applied to compute the one-dimensional nonlinear acoustic wave field in an inhomogeneous medium insonified by a 1 MHz Gaussian pulse propagating up to 100 mm. The results show that the method is able to predict the propagation and the scattering effects of nonlinear acoustic waves in media with inhomogeneities in the coefficient of nonlinearity. This motivates a similar extension of the three-dimensional INCS method.
Three-dimensional calculation of ultrasound propagation through a breast model.
Authors: Tillett Jason C. , Salahura Gheorghe , Metlay Leon A. , Waag Robert C.
Published: March 2010

A specimen of human breast comprised mostly of fat and connective tissue was imaged with a high-resolution magnetic resonance scanner. The volume of data was segmented to construct an acoustic model by assigning values of sound speed, density, and attenuation to voxels corresponding to fat and connective tissue. Propagation of a wavefront from a point source through the model was calculated using a three-dimensional finite-difference time-domain k-space method that included perfectly matched absorbing boundary conditions to eliminate reflections at the edge of the computational domain. Because of the large 557×451×289 grid and computational demands of the three-dimensional FFT, the calculation was performed on a cluster of computers. The wave field was sampled in three orthogonal planes, one of which was offset from the origin to represent a receiving aperture. The aperture waveforms were corrected for geometry associated with the estimated location of the point source and used to calculate arrival-time and energy-level fluctuations. The root-mean-square arrival-time and energy-level fluctuations of the simulated propagation were consistent with measurements for comparable specimens of breast. The results demonstrate the feasibility of using the described combination of methods to provide insight about the way ultrasound beams are aberrated by tissue.
Effects of middle-ear disorders on ear-canal reflectance measures in human cadaver ears.
Authors: Voss Susan E. , Merchant Gabrielle R. , Horton Nicholas J.
Published: March 2010

The development of acoustic reflectance measurements may lead to noninvasive tests that provide information currently unavailable from standard audiometric testing. Few systematic measurements exist on the effects of various middle-ear pathologies on the ear-canal reflectance, where reflectance is calculated from impedance measurements. This work uses a human cadaver preparation to examine how a variety of middle-ear pathologies affect power reflectance: static middle-ear pressures, middle-ear fluid, fixed stapes, disarticulated incudo-stapedial joint, and tympanic-membrane perforations. The change from normal in power reflectance, induced by the simulated pathology, generally depends on frequency and the extent of the pathology (except for the disarticulation). The largest changes from normal occur as increases in power reflectance near 1000 Hz with both large static pressures and large amounts of middle ear fluid. Disarticulation of the stapes results in reductions in power reflectance at the lower frequencies, while fixation of the stapes results in low-frequency increases in power reflectance. Tympanic membrane perforations generally produce reductions in power reflectance for frequencies below 1000–2000 Hz that are systematically related to the size of the perforation. These preliminary measurements may help assess the utility of power reflectance as a diagnostic tool for middle-ear disorders.
In-situ calibrated sound signals and hearing sensitivity.
Authors: Withnell Robert , Jeng Pat , Shofner William , Allen Jont
Published: March 2010

The acoustic input impedance of the ear provides data on the acoustico-mechanical function of the ear and can be used diagnostically to assess outer and middle ear function. Sound signals delivered to the ear (canal) can be quantified in-situ if the complex reflectance of the ear has been determined. Hearing sensitivity can be expressed in terms of the forward-going sound pressure wave, or after correcting for acoustic delay, the fraction of the forward-going sound pressure wave transmitted to the middle ear. The latter is an estimate of the signal the cochlea receives. Data will be presented examining the virtues of expressing hearing sensitivity in terms of an in-situ calibrated sound signal.
Simple models for hearing-aid vents and open fittings.
Authors: Kates James M.
Published: March 2010

The effects of a vent or open fitting are determined by the vent and ear acoustics. The dominant effects are a high-pass filter applied to the hearing-aid frequency response and a low-frequency direct signal path through the vent into the ear canal. Because these effects occur predominantly at low frequencies, simple lumped-parameter acoustics can be used to model them. The vent is modeled as an acoustic mass, and the ear canal and middle ear impedances as equivalent acoustic volumes. The results of using these simple approximations will be compared to calculations using acoustic tube models for the vent and ear canal and the Zwislocki middle-ear impedance model.
A comparison of two methods for estimating sound pressure level at the tympanic membrane at high frequencies for hearing aids.
Authors: Zhang Tao , Recker Karrie , LoPresti Janice , Kleffner Matt , Ryan William
Published: March 2010

For hearing aid fittings, it is important to know the delivered sound pressure level (SPL) at the tympanic membrane (TM) over a wide frequency range. Because it is infeasible to measure the SPL at the TM clinically, an indirect estimation based on measurements away from the TM is often used in practice. Furthermore, it is highly desirable that such a method does not require a clinician to use extra accessories to perform extra calibration in a clinic. Two such methods were proposed in the past. One used a set of empirically derived correction factors to estimate the SPL at the TM (Recker et al. (2009), the other used a lumped-element model to estimate the SPL at the TM [LoPresti et al. (2009)]. In this study, both methods were evaluated using actual hearing aid prototypes. An ITC hearing aid was built for each of ten participants. For each participant, the SPL in the ear canal was measured using a hearing aid microphone. The SPL at the TM was estimated using each method separately. The results were compared with the measured SPL at the TM. The relative strength and weakness of each method were discussed with the implications for clinical applications.
Assess eardrum characteristics using standing wave technique.
Authors: Lin Weili , Recker Karrie
Published: March 2010

It has been shown that eardrum reflection coefficients can be derived accurately up to 8 kHz based on standing wave patterns in the human ear canal, but not as reliably in higher frequencies [Lawton et al., J. Acoust. Soc. Am. 79, 1003 (1986)]. The primary purpose of this study is to investigate various factors affecting the accuracy of this type of measurements and extract important characteristics of ear canal and eardrum. In addition to reflection coefficients, eardrum impedance and the effect of loading on the eardrum are also examined. A model ear canal is constructed using a tube with variable loading conditions at one end. Measurements are taken along the center axis and contour of the tube when a stimulus is presented with frequency components up to 16 kHz, under both occluded and open situations. Results obtained from standing wave properties in the model ear canal are then compared to data acquired in real ear and in an ear simulator.
The banjo, string theory for the rest of us.
Authors: Dickey Joe
Published: March 2010

An analytical model of a five string banjo is used to calculate the dynamic response of a plucked banjo and the subsequent radiation of sound. This is the easy part: the difficult part is to identify and quantify the subtle differences between bad and good sound, whether that sound is measured or calculated. As a step toward this, the author has defined figures of merit (FOMs) to quantify radiated sound characteristics related to loudness, brightness, and decay, and to examine these FOMs as functions of the tension and propagation loss factor of the membranic head, the mass of the bridge, and the location of the pluck on the string. The calculated response does exhibit dual decay constants for radiated sound and a diminution of the sixth overtone. Qualitative agreement between calculated and measured mode patterns will be presented.
Membrane modes and air resonances of the banjo using physical modeling and microphone array measurements.
Authors: Pfeifle Florian , Bader Rolf
Published: March 2010

A fullscale physical model of a banjo is implemented using a finite-difference formulation. The model consists of strings, bridge, resonance membrane, and the air enclosed in the geometry. The resulting time series of plucked strings in the model radiated from the membrane is integrated with respect to a room position in front of the banjo membrane and analyzed. Furthermore, the modes of the membrane are displayed as two-dimensional mode shapes for the plucked string as well as for the free vibrating membrane. For verification and refinements of the model, measurements on a banjo were performed using a 11×11 microphone array. The recorded time series were back-propagated to the surface of the membrane showing its vibrational patterns. These measured modes are compared to the modeed mode shapes in the low- to mid-frequency range. Furthermore, the air modes of the open sound holes are investigated with respect to the their phase relations to the membrane. Radiation strength of these frequencies are strongly influenced by the opposite phase relations of these patterns. Also open-back and closed-back banjos are compared. The radiation behavior of these lower modes in the far field is then used to be implemented into the physical model of the banjo.
Vibroacoustic characterization of a commercial airliner bulkhead.
Authors: Allen Albert , Moeller Mark
Published: March 2010

The commercial airliner bulkhead design candidate of concern is an internal divider wall consisting of an aluminum forward panel and liner aft panel sandwiching an array of closely spaced interstitial aluminum I-beams. The main purpose of the bulkhead, which separates the cargo bay from the occupied area, is to protect the crew from being compromised by cargo during a hard landing. Occupied area noise requirements also affect the bulkhead design as it is a primary path of noise transmission from the cargo bay. Vibroacoustic performance of the bulkhead analyzed with statistical energy analysis is supported by coupon testing of a representative bulkhead test section. Fibrous acoustic treatments were also evaluated experimentally for noise reduction potential. The experimental methods, results, and component level modeling complement each other by demonstrating a vibroacoustically appropriate bulkhead design and good bulkhead modeling practices.
A semi-analytical method to predict the vibroacoustics response of composite and isotropic stiffened panels.
Authors: mejdi Abderrazak , Atalla Noureddine
Published: March 2010

The vibroacoustics behavior of aircraft-type stiffened panels is classically analyzed using deterministic methods such as the finite element and boundary element method at low frequencies or energy based methods at higher frequencies. In the present work, a general semi-analytical method based on modal expansion technique is developed to predict the vibration and acoustics radiation of both metallic and composite flat stiffened panels. Both unidirectional and bidirectional stiffened panels with eccentric stiffeners and various shapes are analyzed using the same matrix formulation. The presented model is also able to predict the response of both regular and irregular stiffened panels. The contributions of the force and moment modal coupling at each beam location are accounted for together with the effect of interaction between ribs in the case of orthogonal stiffened plate. The response to various types of excitations (point force, diffuse acoustic field, and turbulent boundary layer) are presented in terms of their joint acceptance. The model is numerically validated by comparison with the FEM/BEM and hybrid FEM/SEA methods for various configurations and excitations. Excellent agreement is found.
Impact of damping uncertainty on sea model response variance.
Authors: Schiller Noah , Cabell Randolph , Grosveld Ferdinand
Published: March 2010

Statistical energy analysis is commonly used to predict high-frequency vibroacoustic levels. This statistical approach provides the mean response over an ensemble of random subsystems that share the same gross system properties such as density, size, and damping. Recently techniques have been developed to predict the ensemble variance as well as the mean response. However these techniques do not account for uncertainty in the system properties. In the present paper uncertainty in the damping loss factor is propagated through the analysis to obtain more realistic prediction bounds that account for both ensemble and damping variance. The analysis is performed on a stiffened composite cylinder representative of an aircraft fuselage. Realistic bounds on the damping loss factor estimates are determined using measurements acquired on the stiffened composite cylinder in the lab. The analysis demonstrates that uncertainty in system properties, such as damping, should be considered when computing the variance of the response.
Hybrid characterization of engine isolator and its application to cabin noise studies.
Authors: Downing Marshall
Published: March 2010

Aircraft companies typically build a global acoustic model of the aircraft, engines, and engine attachments, which would allow for prediction of cabin noise related to engine operating conditions up to 500 Hz. The objective of the hybrid characterization method is to provide a matrix of stiffness (or mobility) for an isolator over a broad frequency range which is suited for use in the global model. The method is called “hybrid” because it aims at aligning viscoelastic material test data, isolator shaker testing, and a detailed finite element model. The result is a six degrees of freedom matrix of translational, rotational, and cross coupling terms for the engine attachment. This paper covers a case study showing how this method was used for the engine attachments on a business jet aircraft.
From development to evaluating effectiveness in industry: Building a research model for noise control technology efforts.
Authors: Reinke Dana , Smith Adam
Published: March 2010

The NIOSH mining hearing loss research program recognizes the importance of not only developing effective noise controls but also evaluating the technology transfer and industry usage of control technologies. As a way to focus on the direct impact of NIOSH-developed control technologies on reducing noise induced hearing loss, we have developed a structured research model with metrics that help to more accurately evaluate and measure the effectiveness of noise control technologies. Through the development of a process model, we are creating a more structured process to analyze the effectiveness of noise control products through development, refinement, promotion, and long term evaluation stages. With metrics identified at each stage, the model creates a more transparent and consistent process to evaluate control technologies. This presentation describes the architecture of the process model and its associated metrics to reduce occupational noise-induced hearing loss in the mining industry. Proven control technologies for roof bolter and continuous mining machinery will serve as examples of where current research gaps occur and how they are being addressed with this new model. This research structure for noise control development, dissemination, and evaluation of control technology effectiveness can serve as a model for noise control researchers and academics.