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https://www.readbyqxmd.com/read/27915155/vertically-oriented-structure-and-its-fracture-behavior-of-the-indonesia-white-pearl-oyster
#1
Guowei Chen, Hongyun Luo, Shunfei Luo, Zhenying Lin, Yue Ma
Structural calcites, aragonites, and the bonding organic network decide the growth, structure and mechanical properties of the mollusk bivalvia shell. Here, it was found out that the calcite prisms together with the coated organics construct another kind of 'brick and mortar' structure similar to the aragonite tablets. The calcite layer can be divided into three sublayers and direct evidences show that the calcite prisms are produced by two methods: nucleation and growing in the first sublayer; or fusing from the aragonites, which is quite different from some previous reports...
November 3, 2016: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/27915026/effects-of-model-definitions-and-parameter-values-in-finite-element-modeling-of-human-middle-ear-mechanics
#2
Daniel De Greef, Felipe Pires, Joris J J Dirckx
BACKGROUND: Despite continuing advances in finite element software, the realistic simulation of middle ear response under acoustic stimulation continues to be challenging. One reason for this is the wide range of possible choices that can be made during the definition of a model. Therefore, an explorative study of the relative influences of some of these choices is potentially very helpful. METHOD: Three finite element models of the human middle ear were constructed, based on high-resolution micro-computed tomography scans from three different human temporal bones...
November 30, 2016: Hearing Research
https://www.readbyqxmd.com/read/27914448/a-fractional-calculus-model-of-anomalous-dispersion-of-acoustic-waves
#3
Andrew W Wharmby
An empirical formula based on viscoelastic analysis techniques that employs concepts from the fractional calculus that was used to model the dielectric behavior of materials exposed to oscillating electromagnetic fields in the radiofrequency, terahertz, and infrared bands. This work adapts and applies the formula to model viscoelastic behavior of materials that show an apparent increase of phase velocity of vibration with an increase in frequency, otherwise known as anomalous dispersion. A fractional order wave equation is derived through the application of the classic elastic-viscoelastic correspondence principle whose analytical solution is used to describe absorption and dispersion of acoustic waves in the viscoelastic material displaying anomalous dispersion in a specific frequency range...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914447/acoustical-gas-leak-detection-in-the-presence-of-multiple-reflections-dispersion-and-uncorrelated-noise-using-optimized-residual-complexity
#4
A M Ahmadi, A Amjadi, A R Bahrampour, H Ravanbod, S Tofighi
Precise acoustical leak detection calls for robust time-delay estimates, which minimize the probability of false alarms in the face of dispersive propagation, multiple reflections, and uncorrelated background noise. Providing evidence that higher order modes and multi-reflected signals behave like sets of correlated noise, this work uses a regression model to optimize residual complexity in the presence of both correlated and uncorrelated noise. This optimized residual complexity (ORC) is highly robust since it takes into account both the level and complexity of noise...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914446/speech-recognition-for-multiple-bands-implications-for-the-speech-intelligibility-index
#5
Larry E Humes, Gary R Kidd
The Speech Intelligibility Index (SII) assumes additivity of the importance of acoustically independent bands of speech. To further evaluate this assumption, open-set speech recognition was measured for words and sentences, in quiet and in noise, when the speech stimuli were presented to the listener in selected frequency bands. The filter passbands were constructed from various combinations of 20 bands having equivalent (0.05) importance in the SII framework. This permitted the construction of a variety of equal-SII band patterns that were then evaluated by nine different groups of young adults with normal hearing...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914445/coherent-and-incoherent-ultrasound-backscatter-from-cell-aggregates
#6
Romain de Monchy, François Destrempes, Ratan K Saha, Guy Cloutier, Emilie Franceschini
The effective medium theory (EMT) was recently developed to model the ultrasound backscatter from aggregating red blood cells [Franceschini, Metzger, and Cloutier, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 58, 2668-2679 (2011)]. The EMT assumes that aggregates can be treated as homogeneous effective scatterers, which have effective properties determined by the aggregate compactness and the acoustical characteristics of the cells and the surrounding medium. In this study, the EMT is further developed to decompose the differential backscattering cross section of a single cell aggregate into coherent and incoherent components...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914443/converting-sunlight-into-audible-sound-by-means-of-the-photoacoustic-effect-the-heliophone
#7
N B Roozen, C Glorieux, L Liu, M Rychtáriková, T Van der Donck, A Jacobs
One hundred and thirty-five years after Alexander Graham Bell and his assistant Charles Sumner Tainter explored the photoacoustic effect, and about 40 years after Rosencwaig and Gersho modeled the effect in a photoacoustic cell configuration, the phenomenon is revisited in a "Heliophone" device that converts sunlight into sound. The light is focused on a carbon blackened copper coated Kapton foil in an acoustic cell by means of a compound parabolic collimator, and its intensity is modulated by a mechanical chopper...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914442/analysis-and-modeling-of-255-source-levels-of-merchant-ships-from-an-acoustic-observatory-along-st-lawrence-seaway
#8
Yvan Simard, Nathalie Roy, Cédric Gervaise, Samuel Giard
An ensemble of 255 spectral source levels (SSLs) of merchant ships were measured with an opportunistic seaway acoustic observatory adhering to the American National Standards Institute/Acoustical Society of America S12.64-2009 standard as much as possible, and deployed in the 350-m deep lower St. Lawrence Seaway in eastern Canada. The estimated SSLs were sensitive to the transmission loss model. The best transmission loss model at the three measuring depths was an empirical in situ function for ranges larger than 300 m, fused with estimates from a wavenumber integration propagation model fed with inverted local geoacoustic properties for [300 to 1 m] ranges...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914439/design-of-broadband-time-domain-impedance-boundary-conditions-using-the-oscillatory-diffusive-representation-of-acoustical-models
#9
Florian Monteghetti, Denis Matignon, Estelle Piot, Lucas Pascal
A methodology to design broadband time-domain impedance boundary conditions (TDIBCs) from the analysis of acoustical models is presented. The derived TDIBCs are recast exclusively as first-order differential equations, well-suited for high-order numerical simulations. Broadband approximations are yielded from an elementary linear least squares optimization that is, for most models, independent of the absorbing material geometry. This methodology relies on a mathematical technique referred to as the oscillatory-diffusive (or poles and cuts) representation, and is applied to a wide range of acoustical models, drawn from duct acoustics and outdoor sound propagation, which covers perforates, semi-infinite ground layers, as well as cavities filled with a porous medium...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914438/dynamic-sound-scattering-field-fluctuation-spectroscopy-with-singly-scattered-ultrasound-in-the-near-and-far-fields
#10
M L Cowan, J H Page, T Norisuye, D A Weitz
Dynamic sound scattering (DSS) is a powerful acoustic technique for investigating the motion of particles or other inclusions inside an evolving medium. In DSS, this dynamic information is obtained by measuring the field autocorrelation function of the temporal fluctuations of singly scattered acoustic waves. The technique was initially introduced 15 years ago, but its technical aspects were not adequately discussed then. This paper addresses the need for a more complete account of the method by describing in detail two different implementations of this sound scattering technique, one of which is specifically adapted to a common experimental situation in ultrasonics...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914437/humpback-whale-generated-ambient-noise-levels-provide-insight-into-singers-spatial-densities
#11
Kerri D Seger, Aaron M Thode, Jorge Urbán-R, Pamela Martínez-Loustalot, M Esther Jiménez-López, Diana López-Arzate
Baleen whale vocal activity can be the dominant underwater ambient noise source for certain locations and seasons. Previous wind-driven ambient-noise formulations have been adjusted to model ambient noise levels generated by random distributions of singing humpback whales in ocean waveguides and have been combined to a single model. This theoretical model predicts that changes in ambient noise levels with respect to fractional changes in singer population (defined as the noise "sensitivity") are relatively unaffected by the source level distributions and song spectra of individual humpback whales (Megaptera novaeangliae)...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914432/simulation-of-nonlinear-propagation-of-biomedical-ultrasound-using-pzflex-and-the-khokhlov-zabolotskaya-kuznetsov-texas-code
#12
Shan Qiao, Edward Jackson, Constantin C Coussios, Robin O Cleveland
Nonlinear acoustics plays an important role in both diagnostic and therapeutic applications of biomedical ultrasound and a number of research and commercial software packages are available. In this manuscript, predictions of two solvers available in a commercial software package, pzflex, one using the finite-element-method (FEM) and the other a pseudo-spectral method, spectralflex, are compared with measurements and the Khokhlov-Zabolotskaya-Kuznetsov (KZK) Texas code (a finite-difference time-domain algorithm)...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914429/big-brown-bats-eptesicus-fuscus-reveal-diverse-strategies-for-sonar-target-tracking-in-clutter
#13
Beatrice Mao, Murat Aytekin, Gerald S Wilkinson, Cynthia F Moss
Bats actively adjust the acoustic features of their sonar calls to control echo information specific to a given task and environment. A previous study investigated how bats adapted their echolocation behavior when tracking a moving target in the presence of a stationary distracter at different distances and angular offsets. The use of only one distracter, however, left open the possibility that a bat could reduce the interference of the distracter by turning its head. Here, bats tracked a moving target in the presence of one or two symmetrically placed distracters to investigate adaptive echolocation behavior in a situation where vocalizing off-axis would result in increased interference from distracter echoes...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914427/reconstructing-the-normal-velocities-of-acoustic-sources-in-noisy-environments-using-a-rigid-microphone-array
#14
Shang Xiang, Weikang Jiang, Hao Jiang, Jianzheng Gao
An acoustic source identification technique with single layer pressure measurement is presented to reconstruct normal velocities of target sources in noisy environments. The theory for this reconstruction is developed from the inverse patch transfer functions method which is supposed to combine measurements of pressure and velocity on a surface surrounding the source. The rigid microphone array is called an acoustic mask, which is designed to obtain pressure on the Neumann boundary condition and realized by microphones flush mounted on the aluminum plate...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914425/acoustical-standards-news
#15
Neil B Stremmel, Christopher J Struck
American National Standards (ANSI Standards) developed by Accredited Standards Committees S1, S2, S3, S3/SC 1, and S12 in the areas of acoustics, mechanical vibration and shock, bioacoustics, animal bioacoustics, and noise, respectively, are published by the Acoustical Society of America (ASA). In addition to these standards, ASA publishes a catalog of Acoustical American National Standards. To receive a copy of the latest Standards catalog, please contact Neil Stremmel.Comments are welcomed on all material in Acoustical Standards News...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914423/measurement-of-the-low-wavenumber-component-within-a-turbulent-wall-pressure-by-an-inverse-problem-of-vibration
#16
Damien Lecoq, Charles Pézerat, Fabien Chevillotte, Rémi Bessis
An experimental validation is implemented for the measurement of a weak acoustic component within a turbulent wall pressure by an inverse problem of vibration. The turbulent flow is generated by a forward-facing step in a wind tunnel. In addition to the flow, an acoustic source with a low level excites the plate and plays the role of an additional acoustic component to be identified. The inverse methods called the force analysis technique and the corrected force analysis technique are used to compute the wall pressure fluctuations from the measurement of the plate vibration using an array of 13 accelerometers...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914422/modeling-of-oropharyngeal-articulatory-adaptation-to-compensate-for-the-acoustic-effects-of-nasalization
#17
Panying Rong, David P Kuehn, Ryan K Shosted
Hypernasality is one of the most detrimental speech disturbances that lead to declines of speech intelligibility. Velopharyngeal inadequacy, which is associated with anatomic defects such as cleft palate or neuromuscular disorders that affect velopharygneal function, is the primary cause of hypernasality. A simulation study by Rong and Kuehn [J. Speech Lang. Hear. Res. 55(5), 1438-1448 (2012)] demonstrated that properly adjusted oropharyngeal articulation can reduce nasality for vowels synthesized with an articulatory model [Mermelstein, J...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914419/multi-objective-optimization-of-acoustic-black-hole-vibration-absorbers
#18
Micah R Shepherd, Philip A Feurtado, Stephen C Conlon
Structures with power law tapers exhibit the acoustic black hole (ABH) effect and can be used for vibration reduction. However, the design of ABHs for vibration reduction requires consideration of the underlying theory and its regions of validity. To address the competing nature of the best ABH design for vibration reduction and the underlying theoretical assumptions, a multi-objective approach is used to find the lowest frequency where both criteria are sufficiently met. The Pareto optimality curve is estimated for a range of ABH design parameters...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914418/direct-noise-simulation-of-a-canonical-high-lift-device-and-comparison-with-an-analytical-model
#19
Pablo Salas, Guillaume Fauquembergue, Stéphane Moreau
The noise of a canonical main-element/flap high-lift device (HLD) is computed directly using compressible wall-resolved Large Eddy Simulation. An experimental database for the chosen configuration allows us to successfully validate the chosen numerical approach. Both the noise sources and the far-field acoustic pressure are shown to be well predicted. Although the two elements trailing-edge noise can be observed in the near field, the flap remains as the dominant source in the far-field. The simplicity of the studied configuration enables the comparison of the validated numerical results with a recently developed analytical model that takes into account the diffraction of the flap noise by the main-element...
September 2016: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/27914413/differences-in-acoustic-impedance-of-fresh-and-embedded-human-trabecular-bone-samples-scanning-acoustic-microscopy-and-numerical-evaluation
#20
Xiaowei Ojanen, Juha Töyräs, Satu I Inkinen, Markus K H Malo, Hanna Isaksson, Jukka S Jurvelin
Trabecular bone samples are traditionally embedded and polished for scanning acoustic microscopy (SAM). The effect of sample processing, including dehydration, on the acoustic impedance of bone is unknown. In this study, acoustic impedance of human trabecular bone samples (n = 8) was experimentally assessed before (fresh) and after embedding using SAM and two-dimensional (2-D) finite-difference time domain simulations. Fresh samples were polished with sandpapers of different grit (P1000, P2500, and P4000)...
September 2016: Journal of the Acoustical Society of America
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