bluuebunny/crossref_metadata_2025 huggingface dataset:
Transformation acoustics: Theory, ray-tracing, and finite element simulations.
Authors: Gokhale Nachiket , Cipolla Jeffrey , Norris Andrew
Published: October 2010

Norris’ theory of transformation acoustics enables the realization of pentamode acoustic materials having anisotropic density and finite mass. Two additional extensions of the theory are considered, with a view toward demonstrating feasibility for practical applications. First, specializations of the theory developed by Norris [“Acoustic cloaking theory,” Proc. R. Soc. London, Ser. A 464, 2411–2434 (2008)] are considered in order to develop transformations corresponding to pentamode acoustic metamaterials with specified functional forms (constant or powerlaw) for density and stiffness. Ray-tracing and finite element simulations of wave propagation through such pentamode acoustic media are presented. Next, the design of acoustic materials for objects composed of simple geometric shapes (e.g., a cylinder with spherical endcaps) is considered. It is shown that certain classes of transformations are well-suited for the design of such shapes and validate the concept with finite element simulations.
Design and experimental evaluation of particulate composite materials for use as acoustic scattering cancellation layers.
Authors: Guild Matthew D. , Haberman Michael R. , Alù Andrea
Published: October 2010

The possibility of creating acoustic cloaks has recently received significant attention in the scientific community. Many authors have suggested the use of resonant metamaterial layers to achieve functionally graded, anisotropic, and extreme values of density and compressibility to effectively redirect acoustic waves around an object. The need for materials with these exotic properties stems from the use of the coordinate transformation method to design the cloaking layer. An alternative approach to acoustic cloaking, known as the scattering cancellation technique, can be taken in which an elastic cloaking layer is designed to significantly reduce the scattered field over a given bandwidth. Previous work [M. D. Guild, A. Alù, and M. R. Haberman, J. Acoust. Soc. Am. 127, 1952 (2010)] has demonstrated the feasibility of this approach when applied to the case of an isotropic sphere coated with a single isotropic elastic cloaking layer. The current work presents the use of micromechanical models to design multiscale particulate composite materials consisting of micro- and mesoscale inclusions embedded in a continuous matrix. Polymer matrix samples containing varying inclusion volume fractions were constructed and tested to determine the bulk elastic properties using compressional and shear wave time-of-flight measurements. Experimental results validate the use of micromechanical modeling to design acoustic cloaking layers.
Perception of reduced pronunciation variants in conversational speech.
Authors: Ernestus Mirjam
Published: October 2010

Spontaneous conversations are characterized by reduced pronunciation variants that, relative to the corresponding citation variants, provide less acoustic information (e.g., the English word “hilarious” may be pronounced like [hlErEs]). This paper discusses three series of experiments investigating how listeners process reduced variants within their natural contexts. In two series of experiments, native speakers of Northern Dutch listened to extracts from spontaneous conversations in Northern Dutch and either predicted masked reduced words or repeated stretches of speech. These experiments show that even though reduced variants contain little acoustic information, listeners heavily rely on this information. Furthermore, listeners use acoustic cues in the context, which is often reduced itself, and these cues may override semantic/syntactic cues. In the third series of experiments, native speakers of Northern and Southern Dutch listened to conversations in Northern Dutch and indicated whether words appearing on the screen had just occurred in the conversation. The results show that acoustic cues are less informative for listeners who are less familiar with the language variant. These listeners rely more on semantic/syntactic information. In conclusion, acoustic cues, even if highly reduced, play a major role in the processing of conversational speech, especially in native listeners.
Exploring the limits of matched-field processing.
Authors: Debever Claire , Kuperman W. A.
Published: October 2010

Though matched-field processing (MFP) has been shown to successfully localize acoustic sources in an assortment of ocean environments, it has a questionable overall reliability that is still not completely understood. The combination of factors such as signal-to-noise ratio, environment and propagation model accuracy, incoherent versus coherent frequency processing, and the time scales of ocean processes and source/receiver/interferer motion all contribute to MFP performance. Examples of MFP experiments that include results that transition from successful to failed localization are presented and further examined using simulation. Conventional and adaptive methods are included in this study as well as both narrowband and broadband processing.
Sonar transmit and receiver design for detection of underwater objects in nonstationary environments.
Authors: Hamschin Brandon , Loughlin Patrick
Published: October 2010

In undersea environments, particularly shallow water, the sonar backscatter from objects of interest can be subject to propagation effects such as dispersion, attenuation, and multi-path, which can confound detection and classification. Detection and classification of buried objects are further complicated by dramatic changes in the backscatter due to the sediment layer. These propagation and environmental effects can induce time-varying (or nonstationary) characteristics in the received sonar signal. In addition, the object itself can induce nonstationarities, such as the inherent dispersion characteristics of some elastic objects. The processing and analysis of such signals for detection and classification can be enhanced by applying time-varying methods to the received signal, such as time-frequency analysis and linear time-varying filters. Detection can also be enhanced by designing a transmit waveform to optimize some metric, such as received signal-to-interference/noise power. In this talk, we explore the use and benefits of optimum transmit waveform design, and time-varying processing at the receiver, for the detection of elastic objects from their sonar backscatter. [Work supported by ONR, code 321US.]
Physics-based performance prediction model for a coherent communications algorithm.
Authors: Rouseff Daniel , Jackson Darrell R.
Published: October 2010

A demodulation algorithm for coherent underwater acoustic communications may start by applying a finite impulse response (FIR) filter matched to the response of the channel. Relevant design parameters are the length of the FIR filter and the rate at which it must be updated. The performance of the algorithm as a function of these design parameters can then be quantified in terms of the mean-squared error (MSE) in the soft demodulation output. In terms of propagation physics, the length of the FIR filter is related to the number of acoustic paths retained as usable signal, and the required update rate is related to the time variation of the channel. In the present study, scattering by the sea surface is the assumed source of time variation. A model is developed for the MSE as a function of the design parameters. The Kirchhoff approximation is used to model acoustic paths that may have undergone multiple reflections by the sea surface. Required model inputs include the grazing angle, the significant wave height, and the dominant period for the surface waves. Model predictions are compared to published experimental results. [Work supported by ONR.]
Relating acoustic communication performance in different shallow water environments.
Authors: Yang T. C.
Published: October 2010

Relating the performance of an underwater communication system with the signal/environmental characteristics under different environmental conditions is a subject of great interest. Consider a very-shallow water channel, for example, with different wind speeds. The higher the wind speed, the more random the channel (due to sound-scattering from the rough surface), and hence the less the channel coherence-time and the higher the channel-estimation error. For such a channel, one expects the output signal-to-noise (SNR) to decrease inversely with the channel-estimation error; the latter reflects how much of the channel energy is random and treated like noise. On the other hand, the output SNR is expected to be unrelated between different environments where propagation conditions (the multipath arrivals) are significantly different. This paper shows, based on experimental data, that the output SNR (given the same input SNR) is correlated with the channel-estimation error with the same functional relationship despite the environmental differences. The reason is the universal property of the so-called Q function, the auto-correlation of the received impulse responses summed over all receiver channels. The channel-estimation error can thus serve as a metric for performance assessment in different shallow water environments. [Work supported by the Office of Naval Research.]
Sound transmission between rooms with a common plenum: Better predictions from laboratory data.
Authors: Stewart Noral D.
Published: October 2010

ASTM E1414 provides a method of measuring one-third-octave noise reduction between two prescribed laboratory spaces sharing a common ceiling plenum and calculating a single number rating based on those results normalized for a specific amount of receiving-room absorption. However, the noise reduction between two such spaces is dependent on many variables, and E1414 provides no way of relating the measured results to rooms of different geometries. This contrasts with the situation for sound passing through a wall between spaces where the noise reduction (without flanking) depends only on the wall transmission loss, wall area, and absorption in the receiving room. Mariner devised a theoretical equation for the noise reduction through the plenum, but it included the actual transmission loss of the ceiling panels. Starting with that work, a relationship is developed between the normalized noise reduction as measured in E1414 and the actual noise reduction through the ceiling plenum that also depends on the area of the opening between spaces in the plenum, the height and width of that opening, and the absorption in the plenum.
Improvements in impact noise insulation from suspended ceilings.
Authors: LoVerde John , Dong Wayland
Published: October 2010

In high-rise multifamily projects, one of the primary building design decisions from the acoustical perspective is to determine whether or not to install a suspended ceiling at some distance below the structural slab. The acoustical benefits of a suspended ceiling include an improvement of the impact noise insulation of the assembly and reduced flanking transmission; negative aspects of the construction include lower ceiling height, greater building height, and increased initial building cost. The authors analyze field acoustical impact test results in high-rise projects, quantifying the improvements in impact insulation due to top-side resilient matting options and suspended ceiling designs. A summary is presented of the acoustical benefits of suspended ceiling systems compared with the exposed concrete slab condition. The goal of the analysis is to quantify the acoustical benefits of these constructions based on historic field testing to allow for more informed primary building design direction.
Intelligent baffle with variable labyrinth.
Authors: Barroeta Carlos , Ortiz Floriberto R. , Novoa Colin Juan Francisco
Published: October 2010

This is a sound system baffle with a variable window size. The system has an inner electronic circuit working for the acoustic compliance of the box. In low frequencies, the width of the window is the maximum and will change for upper frequencies, thus increasing the acoustic compliance in order to give a better quality in the sounds. The system begins to respond from 100 mA to 5 A. When fully open, the system is closed is at its maximum power.
History of the Acoustical Society of America’s standard on “Underwater Passive Acoustic Monitoring for Bioacoustic Applications”: Metadata issues.
Authors: Thode Aaron , Mellinger David K.
Published: October 2010

In 2005 an ASA working group was formed to examine whether a standard should exist for “Passive Acoustic Monitoring for Marine Mammal Mitigation for Seismic Surveys”. Public discussions at subsequent meetings quickly showed no consensus existed for specifying hardware requirements for passive acoustic measurements, but consensus did seem possible for specifying “minimum requirements for recording and reporting bioacoustic data.” The proposed standard was renamed “Underwater Passive Acoustic Monitoring for Bioacoustic Applications” with three defined goals: (1) providing a set of requirements for information to be documented while recording acoustic data at sea (metadata requirements); (2) detailing the minimum information about acoustic hardware and software to be included when reporting results in gray or peer-reviewed literature; and (3) specifying metrics to be used when summarizing the features of an acoustic signal. After languishing for several years, an attempt is being made to develop the standard further. This presentation describes what ASA standards are, outlines the development process, and sketches the current status of the standard, with an emphasis on metadata issues.
Integrating computer-assistance and human-review to build richly annotated sound libraries.
Authors: Figueroa Harold
Published: October 2010

A current challenge to the effective application of bioacoustic survey methods is the curation and sharing of large collections of sound and metadata, and their integration into a data-analysis workflow that includes computer-assistance and human-review. Computer-assistance affords the annotation of ever larger amounts of data and human-review provides for sufficient quality of annotation and creates a feedback mechanism that supports continuous learning through an ever-expanding collection of training data. I will present some solutions to the above challenges that are being implemented as part of the Bioacoustic Resource Network (BARN) project. BARN provides a web-based interface to annotated sound collections with a back-end computational engine based on XBAT. The solutions provided by the BARN platform contain both technical and social elements. In the technical arena, we consider problems of data-modeling for extensible annotation; strategies for the unique identification of data, derived annotations, and computational resources; the definition of workflow-oriented programming interfaces; and web-service approaches to the larger-scale usability of these annotation libraries. These technical approaches are complemented by network-supported social strategies such as public repositories, open-source licensing, and a developer network. Integration of these technical and social components promises to overcome current challenges and realize the potential of bioacoustic methods.
Construction, calibration, and field test of a home-made low-cost hydrophone system for cetacean acoustic research.
Authors: Romero Vivas Eduardo , León Lpez Braulio J.
Published: October 2010

Marine mammals are reliable bioindicators of aquatic ecosystems health. Since cetacean highly rely on the use of sound for conspecifics interaction, feeding, and navigation, research in bioacoustics becomes fundamental to unravel the influence of anthropogenic activities on their environment and vocal behavior. Unfortunately, the widespread studies in this area are often limited due to lack of affordable equipment. This paper first describes how to build a low-cost hydrophone-amplifier system suitable for cetacean acoustic research and then shows how to perform hydrostatic pressure tests and acoustic calibrations using easily available tools. Finally, field recordings of individuals of two dolphin species: common dolphin (Delphinus spp.) and bottlenose dolphins (Tursiops truncatus) in La Paz Bay, Baja California Sur, Mexico using the proposed system and a professional hydrophone system [AQ-1s and ITC-1042 transducers (10 Hz–100 kHz)] are compared.
Experimental and theoretical studies of microbubble interaction with tissue help optimize drug delivery and imaging.
Authors: Caskey Charles F. , Qin Shengping , Hu Xiaowen , Kheirolomoom Azadeh , Ferrara Katherine W.
Published: October 2010

A multi-disciplinary approach is required to engineer ultrasound contrast agents for drug delivery and imaging. These micrometer-sized bubbles oscillate in response to acoustic energy, emitting non-linear echoes that can be differentiated from the tissue when imaged. If large enough, the oscillations generate perturbations capable of affecting the region surrounding the bubble. Here, microbubble activity is observed in scenarios that mimic those found in vivo to provide intuition about the mechanisms for contrast-enhanced imaging and drug delivery. High-speed imaging of microbubble oscillation at 1 MHz within ex vivo vessels reveals that microbubble expansion is significantly reduced, and the constrained oscillation imparts a force capable of displacing the surrounding vessel wall. [Caskey et al., 122, 1191-1200.] Bubble oscillation near a tissue-mimicking gel boundary shows fluid jets impinging on and disrupting the gel surface at 1, 2.25, and 5 MHz. [Caskey et al., 125, EL183–EL189.] The bubble concentration and acoustic parameters associated with gel disruption and vessel displacement are examined with respect to theoretical predictions, suggesting the ratio of pressure to frequency may be a good indicator for these phenomena. Finally, we also report on extensions of this work to the interaction of targeted contrast agents with tissue.
Biocompatible solid particles for controlled instigation of cavitation during therapeutic ultrasound.
Authors: Arora Manish , Schiffter Heiko A , Manhas Varun , Wagstaffe Sarah , Coussios Constantin C
Published: October 2010

Having been traditionally perceived as an unstable phenomenon to be avoided, cavitation is increasingly found to mediate many beneficial bioeffects, ranging from increased heat deposition during high-intensity focused ultrasound ablation to enhanced drug activity in the context of ultrasound-mediated drug delivery for cancer and stroke. However, due to its stochastic nature, reliable cavitation instigation in vivo is notoriously difficult. Ultrasound contrast agents have been previously exploited to lower the cavitation threshold, but lack stability and are generally too large to readily extravasate into tumors and other target tissues. In the present work, solid biocompatible micro/nanoparticles are proposed as novel cavitation nucleation agents that can overcome the limitations presented by shelled microbubbles. Such solid agents are manufactured from biodegradable polymers by solvent evaporation or by spray freeze drying, in order to achieve high surface roughness and hydrophobicity that harbors cavitation nucleation sites. Changing process parameters makes it possible to create particles of diameters spanning three orders of magnitude (0.15–250 μm) and different surface morphologies. These solid nucleating agents are found to lower the cavitation threshold significantly in water, tissue-mimicking gels, and porcine blood, and to enable reproducible instigation of cavitation activity during repeated exposure of the same target volume.
Ultrasound-enhanced thrombolysis in an ex vivo porcine carotid artery model.
Authors: Hitchcock Kathryn E. , Ivancevich Nikolas M. , Haworth Kevin J. , Caudell Stamper Danielle N. , Vela Deborah , Sutton Jonathan T. , Pyne-Geithman Gail J. , Holland Christy K.
Published: October 2010

Ultrasound enhances recombinant tissue plasminogen activator (rt-PA) thrombolysis via a cavitational mechanism. An ex vivo porcine carotid arterial model incorporating physiologic flow and pressure was developed and stable cavitation promoted for thrombolysis. Aged, retracted whole blood clots were exposed to plasma alone, plasma containing rt-PA (3.15 μg/ml), or plasma with rt-PA and the Definity ultrasound contrast agent (0.31 μl/ml), with and without 120-kHz continuous wave ultrasound at a peak-to-peak pressure amplitude of 0.44 MPa. An insonation scheme was formulated to promote and maximize stable cavitation activity by incorporating ultrasound quiescent periods that allowed for the inflow of Definity-rich plasma. Cavitation was measured with a passive acoustic detector throughout thrombolytic treatment. Thrombolytic efficacy was measured by comparing clot mass before and after treatment. Average mass loss for clots exposed to rt-PA and Definity without ultrasound was 34%, and with ultrasound was 83%, which constituted a significant difference (n = 6, p<0.0001). Without Definity there was no thrombolytic enhancement by ultrasound exposure alone at this pressure amplitude (n = 6, p<0.0001). Acoustic stable cavitation nucleated by an infusion of Definity enhances rt-PA thrombolysis without apparent treatment-related damage in this ex vivo porcine carotid artery model. [Work supported by Grant Nos. NIH R01-NS047603 and NIH T32GM063483, the University of Cincinnati Neuroscience Institute, the Albert J. Ryan Foundation Fellowship, and the Rindsberg Memorial Fellowship.]
The stresses induced by an ultrasound contrast agent oscillation on a micro-vessel wall.
Authors: Hossein khah Nazanin , Hynynen Kullervo
Published: October 2010

Non-inertial oscillating micro-bubbles inside micro-vessels induce some stresses on the vessel walls. It is important to use the bubbles safely and avoid rupturing the vessels. A 3-D model is made of an oscillating micro-bubble inside blood within a micro-vessel. The bubble’s oscillation is implemented for a confined environment. The resulting micro-streaming makes the flexible vessel wall dilate. The vessel wall deformation is simultaneously coupled back to the fluid to make a more realistic model. The vessel walls were modeled as visco-elastic, elastic, and rigid materials. This model is solved using finite element method. Fluid shear stress and circumferential stress on the vessel wall are investigated when the vessel wall rigidity, bubble size, and vessel size are varied. When the size of the bubble increases or the radius of the vessel decreases, both the fluid shear stress and circumferential stress increase. In an elastic vessel (E= 5 MPa, Pa= 250 kPa, f=1 MHz, rv=5 μm), the circumferential stress can exceed the vascular strength (above 800 kPa) when the bubble’s initial size is 3.5 μm or above. The same trend of increasing the stresses is observed when the vessel wall rigidity increases.
Green’s function approach to modeling spherical bubble pulsation between viscoelastic layers.
Authors: Hay Todd A. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Hamilton Mark F.
Published: October 2010

Experiments have shown that bubbles oscillating near surfaces of elastic media experience a translational force whose direction, toward or away from the surface, depends on elastic moduli and standoff distance. [Brujan et al., J. Fluid. Mech. 433, 251–314 (2001).] Bubble translation has also been observed in ex vivo blood vessels following acoustic excitation. [Chen et al., J. Acoust. Soc. Am. 127, 1977–(2010).] A model is developed for a stationary spherical bubble pulsating between two parallel viscoelastic layers. A Green’s function for particle displacement is derived via angular spectrum decomposition and is used to calculate the translational force on a bubble due to pressure reflections from the layers. The predicted dependence of the direction of the translational force on elastic properties and standoff distance is in qualitative agreement with the reported measurements. The reflected pressure is also incorporated in a Rayleigh–Plesset equation for the nonlinear pulsation of the bubble. Evaluation of the Green’s function on the surfaces of the elastic layers yields their displacements due to the bubble pulsations. Predicted surface displacements exhibit characteristics in agreement with wall displacements observed in blood vessels by Chen et al. [J. Acoust. Soc. Am. 125, 2680–(2009).] [Work supported by NIH DK070618.]
Response of polymer-shelled ultrasound contrast agents to static overpressure.
Authors: Chitnis Parag V. , Lee Paul , Mamou Jonathan , Allen John S. , Ketterling Jeffrey A.
Published: October 2010

The static-pressure threshold for rupturing polymer-shelled ultrasound contrast agents (UCAs) manufactured by POINT Biomedical (mean diameter 3 μm, shell-thickness-to-radius ratio (STRR) 7.5 nm/μm, count 961) and Philips Research (mean diameter 2 μm, STRR 40 nm/μm, count 1048) was investigated. The UCAs were subjected to static overpressure in a glycerol-filled test chamber with a microscope reticule lid at the top. UCAs were reconstituted in 0.1 ml of water and added on top of the glycerol surface in contact with the reticule. A video-microscope captured UCA images while glycerol was introduced at 5 ml/h, resulting in overpressure ranging from 2–180 kPa. UCAs were sized using semi-automated post-processing algorithm. The static pressure corresponding to each frame was recorded. Neither UCA population responded to static pressure until the rupture threshold was exceeded, which resulted in an abrupt destruction. The rupture pressure of both UCAs was uncorrelated to diameter. A k-means algorithm divided the pressure data for both UCA populations into three groups: primary, residual, and intact. The three groups exhibited different rupture behaviors although their mean diameters were not statistically different. The results indicated that the Philips UCAs were three-times more resilient to rupture than the Point UCAs. [Work supported by NIH EB006372.]
Subharmonic behavior of targeted and untargeted lipid encapsulated microbubbles at high ultrasound frequencies.
Authors: Helfield Brandon , Cherin Emmanuel , Goertz David
Published: October 2010

Molecular imaging with ultrasound contrast agents (microbubbles) has recently gained interest as a feasible technique for disease-specific imaging, with applications ranging from intravascular ultrasound to small animal imaging. The attachment of targeting ligands to the microbubble shell enables a selective accumulation of bound microbubbles around a target site. The ability, however, to differentiate between the nonlinear signal from bound microbubbles and from unbound, circulating agent still remains a challenge. This study conducts a size-per-size comparison of the acoustic nonlinear response of individual streptavidin-coated MicroMarker microbubbles either bound (BMM) or adjacent (UBMM) to a compliant agarose/biotin gel surface. Bubbles were optically sized and insonified at 25 MHz over a range of pressures and pulse bandwidths. The subharmonic (nonlinear) response between unbound (n = 24) and bound (n = 29) bubbles was found to differ significantly, with UBMM bubbles having a higher propensity to initiate non-destructive subharmonics, in addition to lower onset threshold pressures and a smaller preferentially active diameter than BMM bubbles. In summary, this variability in the nonlinear response of the same bubble type between targeted and untargeted states can have implications for detection strategies, agent fabrication, and contrast imaging quantification for high frequency molecular imaging applications.
Drug uptake by endothelial cells through targeted microbubble sonoporation.
Authors: DeJong Nicolaas , Kooiman Klazina , Harteveld Miranda , Vandersteen Ton
Published: October 2010

Molecular ultrasound imaging uses targeted contrast agents consisting of microbubbles. Drug uptake using microbubbles can be induced by sonoporation, a method that induces transient cell membrane pores by oscillating or jetting microbubbles so that therapeutics can enter the cell. This study focuses on inducing sonoporation with CD31-targeted microbubbles in endothelial cells at low acoustic pressures. Biotinylated lipid coated microbubbles with a C4F10 gas core were made by sonication including CD31 antibody conjugation. Microbubble-cell behavior upon insonification at 1 MHz (6 × 10 cycle sine-wave bursts) at 80, 120, and 200 kPa peak negative acoustic pressure was studied with the Brandaris 128 high-speed camera at a frame rate of 12 Mfs. The cell-impermeable propidium iodide was used as indicator for increased cell membrane permeability due to sonoporation and was detected using fluorescence imaging. A total of 31 cells were studied, wherein all had one microbubble attached per cell. After insonifying the targeted microbubbles at 80, 120, and 200 kPa, only 6 burst of each 10 cycles, 12 cells PI uptake. This study reveals that targeted microbubbles can induce sonoporation. This feature may now be used in molecular imaging using ultrasound, thereby combining imaging and drug delivery.
Structural health monitoring of plate by using ultrasonic Lamb wave and time reversal, multiple signal classification beam forming.
Authors: Han Je-Heon , Kim Yong-Joe
Published: October 2010

The objective of this study is to detect structural defects such as delaminations and notches in a plate by exciting it at a frequency to selectively generate a specific Lamb wave and recording reflected wave signals with a piezoelectric wafer sensor/actuator array. Here, the lowest symmetric (S0) and anti-symmetry (A0) modes are excited by adjusting excitation frequency to increase signal-to-noise-ratio. Note that the measured wave signals consist of the wave signals reflected from the defects as well as the boundaries of the plate. For the purpose of reducing the effects of the reflective waves from the boundaries and pinpointing out the structural defect locations in a high spatial resolution, it is proposed to apply a time reversal (TR), multiple signal classification (MUSIC) algorithm to the measured signals. Through an experimental measurement made with an array installed on a plate, it is demonstrated that the TR MUSIC beam forming procedure can be used to effectively identify the structural defect locations, their relative sizes, and their defect types without significant degradation induced by the boundaries of the plate on the resulting beam forming image.
Identification of noise sources in notebook systems using acoustic holography.
Authors: Cordova Jose
Published: October 2010

The acoustic noise generated by notebook computers is an important quality aspect for consumers. Cooling fans, hard disk drives, and optical disk drives are the main sources of noise in these types of systems. Standard measurement techniques such as sound power or sound pressure are used for measuring the overall acoustic energy generated by a device or the sound pressure at a specific point in space respectively, but give us little information of the location of the noise sources and the transmission paths such as noise leaks. This paper outlines the use of acoustic holography for the identification of noise sources and transmission paths in notebook systems. The setup consists of static reference microphones and a roving array of microphones used to scan the surface above a notebook system. With acoustic holography software, the noise field is constructed and back propagated to the surface where the location of the main noise sources is identified. 3-D iso-surface sound pressure maps and sound intensity maps (passive and reactive) are shown for notebook computers with different airflow system impedances. The technique is validated by reconstructing the radiation characteristics and obtaining the location of elementary monopole and dipole sources.
A directional dogbone flextensional transducer.
Authors: Butler Stephen C.
Published: October 2010

Sonar flextensional transducers, in order to transmit energy in one direction, are combined into arrays of elements that are spaced 1/4 wavelength apart. This spacing is dependent on the sound speed of the water; thus, directionality is reduced as the sound speed changes. Here a single projector that is 1/3 wavelength in size that is capable of developing unidirectional beams and independent of sound speed is described. The directional class VII dogbone flextensional is a modified version of an oval shaped class IV flextensional having a concave shell rather than a convex one. The piezoelectric ceramic stack is a trilaminar bar with two active sections separated by an inactive center section. By driving both sections of the stack in-phase, the shell is driven into an omnidirectional radiation pattern. Driving each stack section 180 deg out-of-phase causes a bending mode in the stack, resulting in a dipole radiation pattern. Driving both sections using complex coefficients determined from the omnidirectional and dipole mode patterns, a cardioid directional radiation pattern is developed. Cardioid patterns are developed over an octave frequency band with a front/back pressure ratio of 50 dB. COMSOL/acoustics module FEA code is used to predict in-water electroacoustic performance and compared with experimental data.
A microelectromechanical systems-based piezoelectric microphone for aeroacoustic measurements.
Authors: Williams Matthew D. , Griffin Benjamin A. , Meloy Jessica , Sheplak Mark
Published: October 2010

This paper describes the packaging and characterization of micromachined piezoelectric microphones designed as aircraft fuselage instrumentation for full-scale noise characterization flight tests. An important requirement for such microphones is a high maximum sound pressure level (SPL) >150 dB coupled with noise floor <45 dB SPL (narrow bin) and flat frequency response in the audio band (20 Hz–20 kHz). In contrast to many past micromachined piezoelectric microphones that use PZT and ZnO for piezoelectric transduction, aluminum nitride (AlN) was used due to inherent advantages in dielectric loss and signal-to-noise ratio. The microphone structure includes a 500–900-μ m diameter circular diaphragm composed of a structural layer and an annular AlN/metal film stack on a silicon substrate. Promising microphone die were selected via laser vibrometer measurements followed by packaging of the microphones and associated electronics in individual 1/4 in. tubular housings. Characterization of the packaged microphones included frequency response, noise floor, and total harmonic distortion measurements. Early results for a packaged microphone reveals a sensitivity of 27 μV/Pa, dynamic range of 36–157 dB, and resonant frequency of 176 kHz.
A micro-machined piezoelectric sensor for monitoring viscosity-variation.
Authors: Choi Sungjoon , Lim Geunbae , Moon Wonkyu
Published: October 2010

A micro-machined piezoelectric sensor is developed for monitoring the viscosity-variation in small amounts of liquid in real time. The device is initially devised for monitoring the state of polymerized chain reaction (PCR) of or ribonucleic acid and being integrated into a Lab-on-a-chip (LOC) since the viscosity may increase with an increase in the amount of DNA with PCR. The sample fluid is assumed to be homogeneous so that the wave propagation characteristics in a micro-channel can be used for measurement. The developed measuring technique is devised to be performed with a small amount of sample liquid and to be able to monitor the viscosity variation in real time. The developed device is composed of two chambers connected by multi-micro-channels and was fabricated using micro-machining technology so that it can be fabricated with other components when it is integrated in LOC. Each chamber has a unimorphic piezoelectric diaphragm; one for generating and the other for sensing sound waves. From the feasibility test performed with test samples (alcohol-water mixtures), it can be shown that the viscosity variation can be measured via a single-frequency driving with the amount of about 13 nl sample. Either continuous harmonic or ton-burst inputs at 4.84 MHz can be used for operating the sensor. [Research supported by R0A-2007-000-20042-0 and 10024719.]
Expo Acustica.
Authors: Tafolla Mrquez José Ángel , Victoria Montserrat Guadalupe
Published: October 2010

During the Expo Austica in 2002, the acoustics academy of the previously mentioned Institute noted the relevance of acoustics study in the country’s development in the industrial, cultural, and intellectual fields, taking into account the areas of application of the mentioned specialty: audio, architectural acoustics, musical acoustics, noise control, bioacoustics, psychoacoustics, vibration analysis, acoustics metrology, and acoustic signal analysis. Since then, such event has been held, each time achieving greater support from the private sector. The objective was to promote scientific and technological advances of the specialty of acoustics in the country’s productive sector. Particular objectives were: (1) disseminate the activities of the specialty within the acoustic National Polytechnic Institute; (2) project the image and work of students and professors specializing in acoustics to achieve successful integration into the labor market; (3) Communicate to the visiting companies that the School of Mechanical and Electrical Engineering at the IPN is a provider of acoustic specialists in Mexico; (4). meet specific applications related to the subject through the conference with support of the team displayed, and display student projects. Location: School of Mechanical and Electrical Engineering of the National Polytechnic Institute unity Zacatenco.
Impulse excitation of the singing rod.
Authors: Gladden J. R.
Published: October 2010

A classic demonstration in acoustics is the excitation of both longitudinal normal modes of a metallic rod. Typically the fundamental mode is excited by holding the bar at the center and stroking the bar with resin coated fingers along the length to excite the first longitudinal mode to a very high amplitude. In this version, several longitudinal modes are excited at once with a broadband impulsive force such as striking the end with a hammer. A mix of the fundamental and higher order tones can be initially heard; however, the higher order modes decay rather rapidly, leaving only the fundamental to ring. Fourier analysis can be used to measure the decay constants of these modes. Further, by choosing rods of identical geometry but different materials (such as aluminum and steel), the different resulting tones can prompt a discussion of the relationship between elastic moduli and sound speed.
The singing shoebox. Part 2: Educational opportunities in a $5 loudspeaker.
Authors: Porter Scott P. , Domme Daniel J. , Whalen Jeffrey S.
Published: October 2010

Moving-coil loudspeakers are an excellent resource for introducing students to acoustics: their widespread use makes them familiar to nearly everyone and the interdisciplinary nature of the device forms a technically rich problem. To exploit this, the authors have created a simple, low-cost loudspeaker in a shoebox to function as both a science project and demonstration. Because of the many technical concepts illustrated by this device, it is an appropriate demonstration for a wide range of academic levels. Already, the shoebox speaker has been used as a teaching demonstration in a previous session [J. Acoust. Soc. Am. 127, 1910]. In this talk, the design and construction of the shoebox speaker will be shown, highlighting the incorporation of everyday materials. The focus of this talk will be on the educational opportunities afforded by this demonstration and its suitability for Project Listen Up. Lastly, the shoebox speaker will be demonstrated.
Ahorra ahora para comprar un carro caro. Speech perception in teaching pronunciation: Learning Spanish liquid phonemes by Chinese, Korean, and Japanese students.
Authors: Espinosa Aída
Published: October 2010

Chinese, Korean, and Japanese students (Asian) have trouble pronouncing Spanish liquid phonemes. The main aims of this research were to prove that speech perception is a requisite to improve the production of these sounds, and that adult Asian students can accurately produce Spanish liquid phonemes if they are guided to change their patterns of perception. This text is based mainly on speech perception studies by Flege and colleagues, [(1995); (2007)] who have found that one of the difficulties experienced by students in the oral production during a second language acquisition is the result of speech perception habits acquired with their first language. The study was carried out with subjects who study at Universidad Nacional Autónoma de México (UNAM). An experimental group was exposed to stimuli to raise their speech perception; other experimental group were given exercises of listen and repeat and given articulatory instructions; a control group was not given any kind of training. The results were assessed by Fisher Exact Probability Test, which allowed us to prove that there exists a strong relationship between learning liquid phonemes and training with speech perception exercises. It is concluded that adult Asian students can improve their pronunciation.
Guitar acoustics research 1980–2010.
Authors: Rossing Thomas D.
Published: October 2010

Although the guitar is more than 200 years old, much of our understanding of its acoustical properties has developed during the past three decades. The low-frequency acoustical behavior can be explained on the basis of the coupled vibrations of the top plate, the back plate, the ribs, and the enclosed air cavity. Prominent peaks in the frequency response can be attributed to reflex coupling between these elements, and the luthier controls the tonal response of the instrument by skillful design and tuning of the various components through adjustment of their stiffness and mass. We discuss some of the more important acoustical research on guitars during the past three decades.
Plucking the string: The excitation mechanism of the guitar.
Authors: Carral Sandra
Published: October 2010

The excitation mechanism of any musical instrument is a key component of the sound production and resulting sound of the instrument. In the case of the guitar, the manner and object with which the strings on the guitar are plucked determine, to some extent, the sound of the instrument. Parameters such as the plucking position, initial displacement, and deformation of the string have a strong influence on the resulting sound and its spectrum. In this talk, these and other parameters, as well as how they influence the sound, will be explained in detail, reviewing the studies available on this subject.
What are the limits of the discrete stringed instrument model?
Authors: French Mark , Jackson Charles
Published: October 2010

Many different analytical models for stringed instruments have appeared in the technical literature, but one of the most widely used is a simple discrete model presented by Christensen and Vistisen in 1980. This model accounts, in a simple and approximate way, for the first two or three modes of a typical stringed instrument such as a guitar and includes coupling between the structure and the enclosed air. For the model to be used in predicting the effect of design changes, it is important to understand its limits. In order to explore the applicablity of the model, we have constructed a fixture that models the volume of an acoustic guitar with rigid side walls and flexible top and back plates, which can be changed quickly. A group of different tops was tested to show the effect of changes in mass and stiffness. Additionally, different soundhole geometries were used. In order to change the interior volume of the body, rigid plates were inserted into the body cavity. We report on the ability of tuned discrete models to account for changes to the geometry and the structure. Further, we show the experimentally determined trends in dynamic response of the guitar fixture.
Internal visualization of finished guitars and their sound.
Authors: Torres J. A. , Granados A. , Hernández G. , García A.
Published: October 2010

The internal structure of two classical guitars (using a near infrared transmittance technique) and typical sound spectra from each were compared. Both guitars were crafted by Paracho luthiers: one with carbon fiber reinforcements, and the other one with traditional Torres design. For the experiments, one fluorescent light bulb was inserted through the soundhole, and after, it was substituted with an incandescent one. The internal structure of each guitar was photographed, using a standard digital camera and a sony camcorder with infrared cut filter (nightshot). A typical song fragment was played in each single guitar, whereas the same experimental conditions were kept. Meanwhile, the corresponding mono record was captured. Sound spectra were averaged using selected fragments from the audio files. The images revealed the internal structure, which were useful in inspecting the internal guitar designs. Spectra of different song fragments played in the same guitar were very similar. However, the spectra did change when playing the same fragments using the other guitar. The procedures here explained allowed are to notice important differences in guitars using inexpensive and easy-to-implement techniques. This infrared photography technique was shown to be a significant improvement in comparison with optical photography; furthermore, it leads one to explore the whole soundbox structure. [Work supported by the Faculty of Engineering (UNAM).]
Studying guitar acoustics with modular software synthesizers.
Authors: Steppat Michael
Published: October 2010

The contructional details of the guitar top plate have a great influence on the percepted sound quality of the instrument. Modeling the whole body with the finite element method provides a good analysis of the mechanical frequency response, with respect to the different spacings of the struts, though it is difficult to calculate it in real time. Modular software synthesizers can be used to simulate the mechanical behavior of the particular components, such as the strings, top-plate, back-plate, and the sound hole. The vibration of each coupled component is calculated real time by a numerical solution of the related differential equations. The results can be used for listening tests to determine the influence of the different individual components.
Acoustic guitar microphone techniques.
Authors: Ortallono Sam
Published: October 2010

This paper will discuss acoustic properties of microphone techniques for the unamplified guitar. By varying only microphone placement and the acoustic properties of the space, we will compare the effects on frequencies captured and reproduced. On and off axis data will be presented as well as those centered on the hole versus the twelfth fret. Also, the recording environment will be tested in both the more and less reverberant states. Mainly the frequency differences will be outlined but some attention will be paid to decay times and constructive or destructive interference. Finally, some examples in context will be delivered to illustrate the strengths and weaknesses of an application for a specific situation. Only one microphone will be presented, as we are only interested in the properties of the placement and the environment rather than microphone choice. No matter the selection of equipment at hand, these techniques will provide guidance to achieve the desired outcome.