bluuebunny/crossref_metadata_2025 huggingface dataset:
The propagation of sound above a hard-backed porous layer.
Authors: Liu Sheng , Li KaI Ming
Published: July 2011

In a recent paper [J. F. Allard, J. Acoust. Soc. Am. 125, 1864–1867 (2009)], the inaccuracy of the classical formulation for the acoustic field of a point source above a hard-back porous layer was addressed. The current study develops a set of closed form analytical solutions for predicting the propagation of sound due to a monopole near a hard backed layer. The current formulation avoids the use of the effective impedance approximation to obtain asymptotic solutions. The asymptotic formulas are derived by applying the method of saddle path integration supplemented by the method of pole subtraction. The analytical solutions are compared with accurate numerical integrations using the fast field formulation and other accurate numerical quadratures. Predicted results suggest that the analytical formulas agree well with exact numerical solutions. Indoor experimental measurements were also conducted to validate the analytical formulas.
Flow and geometry induced scattering of high frequency acoustic duct modes.
Authors: Smith Alex F. , Ovenden Nick C. , Bowles Robert I.
Published: July 2011

Cut-on cut-off transition of acoustic modes in hard-walled ducts with irrotational mean flow is well understood for Helmholtz numbers of order unity, where previous analyzes have shown that the incident mode undergoes a total reflection with a phase shift of π/2. Finite-element simulations of this phenomenon, however, appear to indicate the possibility of energy scattering into neighboring modes at a moderately large Helmholtz number, which can then propagate beyond the transition point. In this work, we attempt to explain and predict such scattering phenomena in slowly varying aeroengine ducts using a multiple-scale approach. It is found that, for sufficiently high frequencies, two mechanisms exist whereby energy can be scattered into neighboring modes by an incident propagating mode. One mechanism occurs only when a mean flow is present in the duct and induces scattering at significantly lower frequencies than the other mechanism that remains present even without a mean flow. An efficient system of coupled ordinary differential equations is developed to obtain the corresponding transmitted and reflected amplitudes of the scattered modes as well as the overall acoustic pressure field. Moreover, the theory appears to demonstrate that some interaction and exchange of energy between the acoustic and mean flow fields occur during scattering.
Acoustical Society of America Silver Medal in Speech Communication
Authors: Pisoni David B.
Published: July 2011

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
Helmholtz-Rayleigh Interdisciplinary Silver Medal in Underwater Acoustics and Engineering Acoustics
Authors: Barger James E.
Published: July 2011

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
Acoustical Society of America Honorary Fellowship
Authors: Bose Amar G.
Published: July 2011

An individual who has attained eminence in acoustics or who has rendered outstanding service to acoustics may be elected to Honorary Fellowship in the Acoustical Society of America.
Soundscape analysis: Need for (automatic) source separation.
Authors: Fiebig Andre , Genuit Klaus
Published: July 2011

The use of psychoacoustics for soundscape analysis is imperative to predict the soundscape from an acoustical point of view. Psychoacoustic parameters as functions of intensity, time structure, and spectral content play an important role with respect to several sensations and yield information with greater differentiation than usually applied indicators within the community noise context. But, with respect to a comprehensive analysis of a soundscape, the exact source constellation must be known. Based on the performance of the human hearing system including intelligent signal processing, a listener can easily focus on a certain source and suppress the noise of other sources, which considerably influences the general appreciation of the whole soundscape. For example, this ability is permanently used to improve speech intelligibility in noisy environments. Therefore, an acoustical soundscape analysis should not just deal with the overall noise, but rather the (psycho-)acoustical properties of the different sources present in a soundscape must be investigated separately. Different methods are conceivable in realizing source separation in complex noise scenarios. The paper will present a few case studies demonstrating the opportunities in separating the contributions of several sound sources within a soundscape.
Developing standard sound measurement and analysis methods to support noise management in parks.
Authors: Fristrup Kurt M.
Published: July 2011

Acoustical conditions in National Parks encompass some of the quietest outdoor conditions ever measured, powerful natural sounds, dense aggregations of visitors, and high traffic roads. Most sites exhibit strong seasonality in natural conditions and visitation. Accordingly, the National Park Service has developed monitoring systems that can accommodate a wide range of conditions, sustain extended periods of continuous data collection, and support a diverse array of metrics. Several years of acoustical monitoring have yielded sound level measurements from 189 sites in 42 units, and measures of noise audibility for 93 sites in 22 units. Comparative analysis of these data revealed substantial diel patterns that are shared across low- and high-noise sites, as well as conspicuous exceptions that can be explained by special conditions at some parks.
Modeling soundscapes: A process of analysis by anticipated sonic content.
Authors: Bettcher Adam D.
Published: July 2011

Through the process of constructing sound maps or soundscapes, the acoustician attempts to describe a particular aural condition using noise-related metrics. Typically, raw-number acoustical data are one means of describing aural conditions; A-weighted sound levels, time-sensitive day-night levels, and octave frequency band analysis are commonly used means of attempting to describe a particular environment by using measurements of sound energy. Many other studies suggest that additional observations of the content of the sonic environment are important when developing descriptors of a given condition. This paper describes a process by which the soundscape is measured and subsequently modeled. Raw acoustical data, in combination with listener observations, are used as a basis for the construction of a probabilistic model that contains both predictions of sonic energy and information on the aural content of a given condition. This combined model is then used to describe and predict aural conditions with a greater potential range of descriptors than those based on raw-number acoustical data alone.
Sound propagation modeling in the ocean for bioacoustics.
Authors: Porter Michael B.
Published: July 2011

A variety of models are available to predict how sound is affected by the ocean channel. The precise waveform may be propagated, leading to distortions within the ocean itself, as well as reflections from the ocean boundaries, and sub-bottom layers. Alternatively, the models can directly predict simpler measures of the waveforms, such as their loudness. The approaches will be surveyed with an ear to which are appropriate for different applications, including marine mammal tracking and modeling soundscapes.
Applications of environmental assessment models for bioacoustic research.
Authors: Siderius Martin , Mountain David , Porter Michael , Houser Dorian
Published: July 2011

In recent years, the authors of this paper have been incorporating acoustic propagation models along with animal behavior models into an open source software package used to assess the risk of anthropogenic sound on marine life. This software package is referred to as the effects of sound on the marine environment (ESME). With little modification, these ESME tools can be applied to address ocean animal bioacoustic research problems. For example, a typical ESME simulation scenario might involve a sonar transmission, propagation, and reception on a field of simulated marine animals (or animats). However, by simply substituting the sonar transmission for an animal call, the receptions from an animal could be simulated on a passive acoustic monitoring (PAM) system. Trivial modifications can be made to include more complicated PAM systems with arrays of hydrophones. This “ESME-in-reverse” approach might be used to estimate important PAM performance metrics such as signal-excess and detection probability. These kinds of performance prediction tools are commonly used in decision aids for navy sonar systems. In this presentation, the ESME tools will be described along with a discussion of how these could be applied to develop PAM decision aids. [Work supported by the ONR.]
Using model-based tracking methods to reduce position uncertainty.
Authors: Nosal Eva-Marie
Published: July 2011

Many marine mammal tracking methods rely on the assumption of a homogeneous sound speed profile. This assumption greatly simplifies the localization problem since solutions can be re-cast as a set of linear equations with closed form solutions for well-defined problems. However, it also leads to increased uncertainties in position estimates. As long as they are accounted for and understood, these uncertainties are often acceptable and the benefits of homogeneous sound speed assumptions outweigh the drawbacks. However, in some cases and applications (such as in shallow water or over long ranges), it is beneficial to use model-based tracking methods that incorporate sound speed profiles. This talk explains some of the concepts and practical issues associated with model-based tracking. It uses simulations and real datasets to investigate and demonstrate the effects of homogeneous sound speed profile assumptions on animal position estimates. [Work supported by ONR.]
Using diffuse ocean ambient noise to synchronize independent elements of a horizontal array.
Authors: Guerra Melania , Thode Aaron M. , Urban Jorge , Swartz Steven
Published: July 2011

Autonomous acoustic recorder packages have been deployed as two horizontal arrays in San Ignacio Lagoon, Mexico, during February and March 2010, to record gray whale (Eschrichtius robustus) sounds. This underwater acoustic environment contains multiple directional anthropogenic sources (passing boats) and numerous biological sources (snapping shrimp) evenly distributed in azimuth around the array systems, in the 0.1–5 kHz frequency range. The local bathymetry surrounding the arrays is highly range-dependent, and the distribution of noise sources is not evenly distributed with azimuth, so extracting a Green’s function estimate from the ambient noise is not feasible. However, extracting information about the relative timing between the independent recorders may be. Estimates of the time derivative of the time-averaged cross correlation between independent elements of each array were computed using both types of continuous ambient noise sources to solve for the recorders relative time offset, clock drift, and physical separation. Acoustic bearings obtained from each array were then used to estimate the two-dimensional position of signals of interest. The ability of the resulting synchronized array system to acoustically localize and track sources is tested using GPS tracks of passing tourist pangas, as well as tracks of a tagged whale carrying both bio-acoustic and GPS tags.
Estimating bowhead whale communications space using measured and modeled data.
Authors: MacDonnell Jeff , Martin Bruce
Published: July 2011

In summer 2009, JASCO deployed ocean bottom hydrophones (OBHs) in the Chukchi Sea to measure natural and anthropogenic noise levels and monitor marine mammals acoustically. Acoustic data were collected from early August to mid October 2009. Ambient data were analyzed to compute noise levels for two sites: a relatively loud and relatively quiet one. Computer modeling was used to determine transmission losses at those sites. Manually acquired statistical data were used to determine average call length, and upper and lower frequencies for bowhead calls. Localization techniques were also used to determine source levels of the calls (Ref. Jonathan/Jeff paper). Using the above information and a modified version of the sonar equation, the space within which bowhead calls remain above ambient can be determined as an indication of maximum communication space. The noise conditions can be modified by simulating a ship passing through the area of an OBH and observing the change in communication space.
Reconstructing echolocation behavior using time difference of arrival localization and a distributed microphone array as a virtual Telemike.
Authors: Knowles Jeffrey M. , Gaudette Jason , Barchi Jonathan R. , Simmons James A.
Published: July 2011

Bats use echolocation to probe their 3-D environment. New techniques in distributed microphone array processing allow us to record echolocation behavior, reconstruct the flight paths, and generate an acoustic record of individual bats flying the laboratory or the field. Probabilistic methods of time difference of arrival localization allow us to follow bats navigating in flight room mazes, foraging in the wild and using active sonar in the presence of possible jamming from conspecifics. By reversing the localization operation, we back out the changing propagation times of the sounds emitted by bats flying fast in three dimensions. Through beamforming, we then create an amplified acoustic track that follows the reference frame of the bat, amounting to a virtual Telemike based on consensus data from the microphone array. Spatial tracking and virtual on-board recording allow us to ask new questions about the spectral and temporal strategies employed by echolocating bats and to model the neural and perceptual natures of sonar. [Work supported by ONR and NSF.]
A simple autocorrelation method for multipath localization techniques.
Authors: Valtierra Robert D. , Van Parijs Sofie M. , Holt R. Glynn
Published: July 2011

A simple method was developed to extract time of arrival information from overlapping direct and reflected acoustic signals using an autocorrelation algorithm in order to localize marine mammals with the direct-reflected time difference of arrival (DRTD) technique. DRTD has up to now been limited to pulsed signals such as whale or dolphin clicks where individual direct and reflected signal arrival times are separated in time and thus easily identified. Using autocorrelation, longer duration signals such as a frequency sweep or whale up-call could be analyzed by DRTD, expanding its compatibility to a larger range of signal types. This correlation-modified DRTD technique was applied to simulated and previously acquired experimental data. Both the simulations and experiments represented localization cases involving bottom-mounted receivers with a single acoustic source at multiple known locations. Experimental data came from autonomous acoustic recording units deployed in the Stellwagen National Marine Sanctuary with an acoustic transducer used to broadcast frequency sweeps.
Correlation between the pulse wave and the blood echogenicity in the radial artery.
Authors: Bok Tae-Hoon , Li Ying , Paeng Dong-Guk , Kang Hee-Jung
Published: July 2011

Pulsatile flow generated by the cardiac motion results in the complicated hemorheological phenomena in the artery. The pulse wave in the radial artery is utilized for the measurement of tonometry and the diagnosis of various diseases by the oriental medical doctors. In this paper, the pulse wave obtained from the three-dimensional (3-D) pulse wave analyzer was compared with the blood echogenicity and vessel diameter in the radial artery using an ultrasound biomicroscopy system. The ultrasonic data were acquired for five subjects and the left wrist of each subject was put on the wrist-rest of the 3-D pulse wave analyzer measuring the pulse waves for 25 s. The repetitive measurement was performed eight times for one of the subjects. The blood vessel motion and the blood echogenicity were calculated from the cross sectional B-mode images of the radial artery. The cyclic variation of the vessel diameter and the blood echogenicity was measured during cardiac cycles. The phases between both of them were opposite each other, and the cyclic variation of the vessel diameter showed the similar pattern with that of the pulse wave. These correlations can be helpful for the diagnosis of the cardiovascular diseases. [Work was supported by Grant no. NRF-2010-0017078.]
Effects of diffraction correction on local attenuation estimation.
Authors: Ghoshal Goutam , Lavarello Roberto J. , Oelze Michael L.
Published: July 2011

Quantitative ultrasound (QUS) techniques have been widely used to estimate morphological and mechanical properties of tissue microstructure for specified regions of interest (ROIs). QUS parameters are obtained by fitting theoretical models to backscatter coefficient (BSC) estimates. To estimate BSCs accurately, precise estimation of attenuation coefficient is necessary. A common assumption when estimating attenuation coefficients using focused transducers is that diffraction and attenuation effects can be decoupled. In this work, the validity of this assumption is investigated for various focused transducer geometries. The transducer beam pattern is modeled using multi-Gaussian beam model and O’Neil’s theory. The backscatter response is then modeled using the Wigner transform of the beam pattern in conjunction with the stochastic wave equation within the single scattering formalism. Experimental results are shown from tissue mimicking agar phantoms with embedded glass beads. The results indicate that the percentage error in estimating local attenuation increases when ROIs are away from the focal zone in the sample. The results obtained using the Multi-gaussian beam model were then compared with other algorithms generally used to estimate local attenuation. [This work is supported by NIH R01EB008992.]
Experimental measurements of ultrasonic scattering for characterization of porous media.
Authors: Vejar Elaine S. , Chandra Kavitha , Thompson Charles
Published: July 2011

Experimental measurements of ultrasonic scattered field from porous media representative of biological tissue such as trabecular bone are discussed in this work. The experiment consists of a water tank containing degassed water at room temperature where the phantom to be analyzed is immersed. The sample is insonified using a 5-MHz unfocused transducer (ULTRAN WS37-5) driven by a pulser/receiver unit (Panametrics-NDT 5077PR) at a pulse repetition frequency of 200 Hz. The backscattered field is measured at a millimeter spatial resolution in the lateral direction and recorded using an oscilloscope (Agilent 54621S). In addition, the angular dependence of the scattered field at a fixed radius is also obtained. Measurements are compared to results from computational methods that provide estimates of the scattered pressure field under strong scattering conditions. The motivation of this work is to better understand trabecular bone scattering properties for clinical use in the diagnosis of osteoporosis.
Effect of low intensity pulsed ultrasound on mesenchymal stem cells.
Authors: Ruan Jia-Ling , Wang Yak-Nam , Crum Lawrence A. , Mitchell Stuart B.
Published: July 2011

Low intensity pulsed ultrasound (LIPUS) has been used to accelerate tissue regeneration; however, the biological mechanisms of LIPUS induced regeneration is not completely understood. The aim for this study is to elucidate the mechanical effect generated by US for the stimulation of mesenchymal stem cells (MSCs). MSCs were cultured on flexible cell culture membranes and stimulated by US for 10 min daily with acoustic intensities of 0, 6, 13.5, and 22.5 W/cm2. Cell proliferation and viability were evaluated by direct cell count and Alamar Blue assay. Morphological evaluation was performed and cell-matrix interactions were evaluated. Cell-matrix interaction was analyzed by immunochemical staining of focal adhesion proteins. LIPUS enhanced cell proliferation at higher intensities and there was an increase in cell viability after 4 consecutive days of US treatment. No morphological changes were observed in all treatments. Expression of focal adhesion protein, vinculin, was enhanced after 3 consecutive days of ultrasound treatment. Studies of media agitation did not show any enhancement effect in cell proliferation or focal adhesion protein expression. The results validates that US is able to influence the cell matrix interaction. Application of higher acoustic pressure on cell growth environment can stimulate MSC proliferation and focal adhesion.
Cavitation damage during sonothrombolysis using high intensity focused ultrasound.
Authors: Weiss Hope L. , Ahadi Golnaz , Hoelscher Thilo , Szeri Andrew J.
Published: July 2011

High intensity focused ultrasound (HIFU) has been shown to accelerate thrombolysis, in vitro and in vivo, for treatment of ischemic stroke. Stable and inertial cavitations are thought to play an important role in sonothrombolysis, even though the mechanisms are not fully understood. Possible mechanisms associated with both stable cavitation (i.e., microstreaming) and inertial cavitation (i.e., microjets) are thought to increase clot lysis by enhancing the delivery of a thrombolytic agent. The damage to a blood clot\textquoteright{}s fiber network from bubble collapses in an HIFU field is studied. The region of damage caused by a single bubble collapse on the fiber network of the blood clot exposed to HIFU is estimated and compared with experimental assessment of the damage. The mechanical damage to the network is estimated using two independent approaches: a fiber deformation based method and an energy based method. Whole human blood clots under flow conditions are exposed to 220 kHz ultrasound using the ExAblate 4000. During HIFU exposure, passive cavitation detection is performed using a wide band (10 kHz–15 MHz) hydrophone. Scanning electron microscopy is used to assess the region of damage experimentally. [Work supported in part by NSF Graduate Research Fellowship.]
Bubble dependence of the mechanism FUS-induced blood-brain barrier opening in mice in vivo.
Authors: Tung Yao-Sheng , Fotios Vlachos , Selert Kirsten , Konofagou Elisa
Published: July 2011

The activation of bubbles by an acoustic field has been shown to temporarily open the blood-brain barrier (BBB) but the physical effects responsible for BBB opening remain unknown. In this study, the physical mechanism of the FUS-induced BBB opening with monodispersed microbubbles is unveiled. Sixty-seven mice were injected intravenously with bubbles of either 1–2, 4–5 or 6–8 μm in diameter. The right hippocampus of each mouse was then sonicated using focused ultrasound (1.5-MHz frequency, 100-cycle (67 μs) pulse length, 10-Hz pulse repetition frequency, and 1 min duration). Peak-rarefactional pressures of 0.15, 0.30, 0.45, or 0.60 MPa were applied to identify the threshold of BBB opening and inertial cavitation (IC). It was found that the BBB opens with nonlinear bubble oscillation when the bubble diameter is similar to the capillary diameter and with inertial cavitation when it is not. The bubble may thus have to be in contact with the capillary wall to induce BBB opening without IC. The BBB opening was induced safely with nonlinear bubble oscillation at the pressure threshold for opening while its volume was highly dependent on both the acoustic pressure and bubble diameter. [This work was supported by NIH Grant No. R01EB009014 and NSF Grant No. CAREER 0644713.]
Ultrasound-induced permeability variations in cell gap junctions for drug delivery.
Authors: Anastasiadis Pavlos , Allen John S.
Published: July 2011

An improved understanding of endothelial cell permeability changes at the molecular level has the potential to significantly improve our insights into inflammation and treatment of associated cardiovascular diseases. The relationship between integrin-mediated variations in gap junction behavior and the empirically observed ultrasound-induced pore formation on the surface of plasma membranes are not well understood. More rigorous experimental comparisons with statistics with regard to pore formation and pore size distributions are needed to discern the underlying molecular mechanisms in order to optimize drug delivery applications. Human coronary artery endothelial cells (HCAECs) were grown to confluency. Long-term electric cell-substrate impedance sensing measurements were conducted in real-time and under physiological conditions. The HCAECs were subsequently irradiated with ultrasound over a range of clinically relevant parameters. Complementary scanning electron microscopy was conducted to quantify pore formation. The antibodies to integrins β3 and α2β1 change endothelial permeability from the normal values of 3.8 ± 0.5 Ω cm2 to 2.4 ± 0.6 Ω cm2. For an acoustic pressure of 0.1 MPa, the mean pore size was found to be 0.019 μm2 while at a pressure level of 0.3 MPa the corresponding value increased to 0.024 μm2 with considerable differences in the respective size distributions.
Self-assembly of ultrasonically synthesized gold nanoparticles on protein microbubbles for multiple imaging applications.
Authors: Cavalieri Francesca , Zhou Meifang , Teo Boon Mian , Grieser Franz , Ashokkumar Muthupandian
Published: July 2011

Air-filled lysozyme microbubbles can be synthesized in an aqueous medium by emulsification followed by cross-linking of protein molecules under high-intensity ultrasound. The efficiency of formation, size distribution, and morphology of the microbubbles can be controlled by manipulating the experimental conditions, namely, power and length of sonication [Zhou et al., Soft Matter (in press); Med Cavalieri et al., Current Topics in Medicinal Chemistry, 12, 1198–1210 (2010)]. Gold nanoparticles have been sonochemically synthesized and stabilized with bovine serum albumin and polyvinylpyrrolidone. Gold nanoparticles (NPs) have been assembled on the surface of microbubbles in a deposition process. The functionalization of the surface of bubbles endowed the microbubbles with gold plasmon absorption and fluorescence emission. The NP-coated bubbles showed enhanced response when irradiated by 1 MHz ultrasound. We envisage that these stable, multifunctional microbubbles may have important applications in medical diagnostics where multiple imaging methods using a single contrast agent can be advantageous.
Use of high intensity focused ultrasound for localized activation of thermosensitive liposomes for drug delivery.
Authors: Mannaris Christophoros , Efthymiou Eleni , Escoffre Jean-Michel , Bouakaz Ayache , Khokhlova Vera A. , Ilyin Sergey A. , Averkiou Michalakis A.
Published: July 2011

Localized drug delivery holds great promise in improving drug efficacy in cancer treatment. Newly developed temperature-sensitive liposomes (TSLs) loaded with doxorubicin have been shown to release their payload with mild hyperthermia near their phase transition temperature (Tm = 43–45 °C). In the present work, high intensity focused ultrasound is used to induce the required temperature elevation for the release of the drug from TSLs. A theoretical model based on Pennes’ bioheat equation was initially used to calculate the conditions for temperature elevation in fluids and tissue phantoms under conditions for drug activation. Acoustic pressures of 1–2 MPa at the focus with varying duty cycle (typically 50%) at 1 MHz frequency were calculated. Measurements of temperature rise were found in good agreement with our theoretical predictions. Fluorescence measurements were used to assess the release of free doxorubicin that exhibits higher fluorescence intensity than the liposomal formulation. In vitro experiments of drug delivery using doxorubicin-loaded TSLs and HIFU were performed with BLM and U-87 MG cancer cells that were seeded in Opticell™ chambers or suspended in polystyrene cuvettes. Trypan blue cell viability assay was used to evaluate the drug release and uptake. Ultrasound-induced TSL activation increased cell mortality considerably.
Scattering and attenuation from an emulsion of echogenic liposomes.
Authors: Paul Shirshendu , Nandy Tapas , Mallik Sanku , Sarkar Kausik
Published: July 2011

Liposomes are nanoparticles (diameter 50 nm–10 μm) formed by a self-assembling lipid-bilayer encapsulating an aqueous phase. Due to their structure similarity to cells, they show many advantages in medical applications such as lesser toxicity, prolonged circulation, and greater uptake in target organs or tumors. They are ideal as drug delivery or image enhancing agents. Recently, echogenic liposomes (strong scatterers of ultrasound) have been developed for contrast ultrasound imaging. However, the mechanisms for the observed echogenicity—unlike contrast gas microbubbles, liposomes contain mostly an aqueous phase inside and water outside—remain uncertain. In this talk, size distribution as well as acoustic properties such as attenuation of and scattering from an emulsion of echogenic liposomes will be reported. The attenuation depends linearly on the liposomal concentration indicating absence of multiple scattering. The scattered response from the liposomal solution contains a subharmonic component much weaker than the second harmonic component. Reduction in mannitol concentration in the preparation of echogenic liposomes leads to decrease in polydispersity of the emulsion and affects echogenicity. Encapsulating the dye 5(6)-carboxyfluorescein as a model for hydrophilic drugs reduces echogenicity by 10 dB. [Work supported by NSF.]
Transducer design synthesis.
Authors: Marshall William J.
Published: July 2011

Traditionally underwater sound projectors are designed by repeatedly exercising an electroacoustic model of a proposed device. Given properties of the environment, chosen materials, and controlling dimensions of the device, one can prepare a model that will predict its mechanical and acoustic performance. Reaching the design goals involves iteration of the model to find that particular mix of dimensions which best satisfies all requirements. The inverse of this process, a design synthesis method (DSM), makes the design process more efficient. In a DSM the environment, materials, and desired mechanical and acoustical metrics determine critical dimensions of a device optimized for meeting those requirements. Following this step regular electroacoustic modeling is used to calculate remaining aspects of the optimized design’s acoustic and mechanical performance. Inverting the design equations to develop a DSM for the flextensional class of transducers would appear to be a daunting problem; however, it can be solved rather easily using the nonlinear goal-seeking algorithms available in mathematical tools such as MATLAB and MATHCAD. This talk will present a brief description of the relevant math problem and its solution.
Investigation of a balanced-armature transducer for vibrational energy harvesting.
Authors: Vitt Nikolas T. , Thompson Stephen C.
Published: July 2011

The ability to sustain or prolong the operation of devices which require electrical power by utilizing ambient energy is desirable in many applications. While a variety of transducers have been considered for harvesting vibrational energy, the balanced armature transducer has yet to be fully investigated for such purposes. Balanced armature transducers, such as those used in hearing aids, are promising as they offer a compact design and are commercially available. An analog circuit model for a commercial hearing aid transducer has been modified to include a vibration input and the results are compared with experiment. Using this model, the performance of the transducer can be assessed before and after possible design modifications are considered. [This work was sponsored by the Office of Naval Research.]
Variations in standard couplers used in measurement of earphones and hearing aids.
Authors: King Charles B.
Published: July 2011

In comparison to balanced armature transducers designs for ear phones and hearing aids, it is common to be have specifications that are tighter than +/−3 dB and be interested in differences between devices of less than 1 dB. Very often, measurement facilities will be scattered across the globe and thus it becomes very important to understand variations in the “standard” measurement couplers used. While couplers are standardized in IEC and ANSI and work seamlessly when looking for 5-dB variations; higher precision measurements require greater care. The user must be very aware of numerous variations possible and allowed within the standard and influenced by aspect ratios of the couplers, differences in the tuning at manufacture of the coupler, and barometric pressure at different locations. Measured data as well simulated data will be shown to help understand the range of potential errors and the frequency bands in which they occur.
Transduction in acoustically actuated carbon nanotube Structures.
Authors: Deschamp Barbara , Chandra Kavitha , Thompson Charles
Published: July 2011

A model of the process of mechanical to electrical energy transduction in a carbon nanotube (CNT) clamped between two metallic junctions and suspended over a substrate-backed gate electrode is presented. The CNT that is driven into resonant mechanical vibrations by an external acoustic field exhibits charge transport characteristics that are dependent on the transverse length scale of the CNT relative to the mean free path of the charge carriers. A circuit model that captures the ballistic transport features and Coulomb interactions as the CNT dimension decreases to the order of atomic scales is presented. The current resulting from the acoustically induced mechanical vibrations of the CNT depend not only on the time-varying capacitance between the CNT and gate electrode, but also on the probability and tunneling rate of a carrier through the junctions and into the CNT. The coupled effect of the resistance and capacitances of the tunnel junctions on the mechanical vibrations of the CNT and resulting charge transport are analyzed. [B.D. acknowledges support from GK-12 fellowship through National Science Foundation Grant No. 0841392.]
The hose-o-phone: A quasi-musical instrument.
Authors: Moore Thomas
Published: July 2011

A musical instrument made from rubber tubing and a plastic funnel can be used to demonstrate several important acoustic phenomena. This presentation will focus on the important physics that can be demonstrated using this simple and inexpensive “musical” instrument.
A research-based approach to teaching the basic concepts of musical instruments with low cost instruments.
Authors: Adams Wendy K.
Published: July 2011

A week long unit covering the basic concepts of musical instruments/voice (source of vibration, resonance, and a way to change pitch) will be presented. Students often do not pick up on these basic ideas of musical instruments from a straight forward clear lecture. Physicists typically are trying to teach them why instruments work, which means focusing on what is common about all instruments. While typically their previous instruction (music classes, for example) tried to teach them how to categorize instruments focusing on what is different. It appears that this prior instruction, and the fact that sound waves are invisible make this a difficult topic for students. The unit includes the use of a homemade straw instrument, cup instrument, and reed instrument. Students compare and contrast different types of instruments in an attempt to generalize the necessary characteristics of musical instruments. They also investigate their own voices, an interactive simulation on resonance, and an interactive lecture demonstration on resonance (pasta and raisins).
A simple high school Lloyd’s mirror experiment: The difference between theory and experiment.
Authors: Dean Cleon E. , Smith Joshua A.
Published: July 2011

A baffled circular loudspeaker is driven at 10 000 Hz to provide a sound source for a high school level Lloyd’s mirror experiment. The experiment was to be performed in an ordinary building hallway. The experiment was also designed to produce interference using reflected sound from a hard floor while avoiding reflected sound from other surfaces. Modeling the sound as a Fresnel volume proved useful, but certain assumptions about the effectiveness of sound absorbing tile and flat foam rubber mats were less so. Substitution of more effective sound absorbing materials gave improved results when reflected sound was to be eliminated or the interference effect annulled.
Formant strategies in professional male singers.
Authors: Sundberg Johan , L Filipa , Gill Brian
Published: July 2011

Singers use formant tuning to avoid discontinuities in voice quality between registers. Around the passaggio, a set of spectrum characteristics has been identified as important to achieve this register equalization. Previous studies suggest different formant tuning strategies in male voices. The present investigation attempts to corroborate these suggestions experimentally. Eight professional tenor or baritone singers sang ascending scales on the vowels [a, æ, i, u] ending on pitches F4, F4, or G4 (350, 370, and 392 Hz, respectively) and including their passaggio notes. These scales were sung with two different formant strategies: (a) as in their normal classical singing technique and (b) as in a non-classical, musical theatre style. Formant frequencies were measured using the custom made DECAP inverse-filtering software (GRANQVIST). Results revealed formant tuning differences between the two styles. For the classical singing technique, systematic changes of formant frequencies with pitch were observed. For the back vowels F1 was adjusted to a frequency below the second partial and F2 to the vicinity of the third, confirming previous observations. Formant frequencies were often quite close to a partial. The major spectrum characteristics could be accurately replicated by synthesis applying the source filter theory of voice production.
Absolute pitch is correlated with high performance on relative pitch tasks.
Authors: Dooley Kevin , Deutsch Diana
Published: July 2011

Absolute pitch (AP)—the ability to name a musical note without a reference note—has been shown to be associated with an advantage in pitch identification tasks; however, its usefulness in contexts involving relative pitch has so far been unclear. To explore this issue, 36 trained musicians—18 AP possessors and 18 non-possessors with equivalent age of onset of musical training and duration of musical training—were tested on several different interval naming tasks requiring only relative pitch. AP possession was highly positively correlated with performance on these tasks; r=0.72, p less than 0.001. Furthermore, the advantage of AP possession in performing these tasks was not dependent on musical key, interval size, or musical context. These findings support the hypothesis that AP may be beneficial in performing musical tasks including those that primarily require the processing of relative pitch.
Relative harmonic magnitude extraction for musical instrument detection.
Authors: Oh Sejin , Choi Jeung-Yoon
Published: July 2011

Harmonic structure is widely used for assessing the timbre of pitched musical instruments. However, fundamental frequency and overtones are not easy to extract due to spurious partials and missing fundamentals. This study attempts to extract underlying harmonic structure based on source-filter modeling. The spectral envelope is first extracted by linear predictive analysis. To discard spurious partials, the source is divided out using noise level estimation, yielding harmonic structure characteristic to particular instruments. The resulting relative harmonic magnitudes, as well as the spectral envelope, are used to classify musical instruments. Experiments were conducted on the RWC musical instrument sound database. Results show that features are preserved for each musical instrument, over varying pitches.
Discrimination of instrument tones resynthesized with piecewise-linear approximated harmonic amplitude envelopes.
Authors: Lee Chung , Horner Andrew , Beauchamp James W.
Published: July 2011

Harmonic amplitude envelopes of instrument tones were approximated using piecewise-linear segments to investigate how the discrimination of approximated sounds varies with the number of breakpoints and instruments. Listening tests were done to determine the discrimination of the approximated sounds from the originals. Apart from basic statistical analysis, various error measurements were evaluated based on the results of the listening tests. Relative-amplitude critical band error was the best error metric, accounting for about 82% of the discrimination variance. Strong correlations were found between the discrimination scores and spectral incoherence, with breath noise in the flute and bow noise in the violin particularly discriminable in piecewise-linear approximation.
Ecma International Acoustic Standard Activities: An enabler for controlling information technology noise emissions.
Authors: Robert D. Hellweg , Egons Dunens , Baugh Eric
Published: July 2011

Ecma International is an organization that facilitates the timely creation of a wide range of standards for Information Technology (IT) products, including acoustics standards. Ecma standards have a history of short development time and revision. Each Ecma acoustics standard will be discussed demonstrating how it promotes the analysis and control of IT product noise. ECMA-74 is the test code for sound emissions from IT equipment. Annex C includes uniform operation and installation conditions for most types of IT equipment and is now referenced by the latest versions of ISO 7779:2010 and ANSI S12.10. This reference by other standards ensures that there is a world-wide consistency on mounting and operating conditions and that these procedures are up to date. The latest edition of ECMA-109 on noise declarations for customers presents revised guidelines to manufacturers on making declarations when testing a small sample size. ECMA-108 presents methods for determining high frequency sound power and has been submitted to ISO for revision to ISO 9295. ECMA TR/275 on measuring fan structure-borne noise was the basis of ANSI S12.11/Part2 (ISO 10302/Part 2). ECMA TR/99 covers constant sound power fan curves to assist product developers to select low-noise operation of fans at realistic operating points.
Measuring printer impulses using high frequency spectral content.
Authors: Ferguson Katy
Published: July 2011

Printer impulsive noise significantly contributes to the overall product sound quality. Printer manufacturers are seeking accurate impulsive metrics to understand and quantify customer perceptions and acceptability criteria. Numerous research papers [Baird, Inter-Noise 2005; Ali and Bray, NoiseCon 2004; etc.] have correlated both IT specific and general impulsive metrics to listening test results. These studies show that impulsive metrics that factor in frequency content have high correlation to user perception. This paper discusses the development and verification of a high frequency spectral content printer impulsive metric. This calculation excludes impulsive amplitude, using only the frequency content as a measure of user acceptability.
Overview of notebook fan noise reduction efforts.
Authors: Baugh Eric
Published: July 2011

Notebook computers face particular challenges with regard to cooling the interior components and the surface of the chassis that is in contact with users, in addition to being operated in a wide range of thermal and acoustic ambient conditions. Fan airflow is responsible for about 85% of the cooling capability in typical designs, and is in turn limited by acoustic considerations. This paper will review fan-level and system-level efforts by Intel Corporation to promote low noise fan and system designs. Test fixturing to emulate the restricted space inside a notebook computer, combined with an ISO 10302 plenum, can be used to generate constant sound power fan curves, which capture multiple aspects of fan performance. It can be shown that the optimum design is different for the installed condition than for the free space condition where noise is typically reported today. At the system level, the chassis impedance is intimately connected to the airflow at a chosen noise limit. The location of the fan exhaust relative to the LCD panel can influence the operator position noise. Active control of fan noise has also been demonstrated in a notebook computer.
Multichannel algorithm for zone to zone active noise control (ANC) application.
Authors: Rubin Ofira , Cherkassky Dani , Maron Ido
Published: July 2011

Multichannel acoustic active noise control (ANC) systems are increasingly being developed in order to overcome the limitations of the standard loudspeaker and to increase the spatial extents of the quiet zone. The method is to synthesize the physical characteristics of the unwanted noise field in an extended listening area. Multichannel algorithm allows controlling the sound field produced by loudspeakers array. This paper presents a multichannel algorithm technique based on filtered-x LMS algorithm. The technique selected for this optimization problem is taking into account the effect of secondary sources coupling used for control purposes. The effectiveness of multichannel ANC algorithm using loudspeakers array and one sensor in a real system was verified. A quiet zone noise reduction of 6 dBA was demonstrated in 50-cm diameter for broadband signal.
Active control of centrifugal fan noise: Experimental results.
Authors: Boyle John K. , Esplin J. James , Sommerfeldt Scott D. , Gee Kent L.
Published: July 2011

Previous work by these authors in active control of axial fans suggests an approach that can be successful in applying active control to small centrifugal fans used in fan trays and laptop computers. The modeling and analysis strategies developed for axial fans were modified for use with centrifugal fans mounted in a rectangular exhaust duct. Experimental verification allowed for proper inclusion of damping in the model. By minimizing the sound power radiated from the duct, optimal error sensor placement was predicted. Experimental results verified the effectiveness of placing the error sensor at these locations. Using predicted control source and error sensor locations, the rectangular duct was replaced by a centrifugal fan and duct attached to a heat sink, with the total dimensions being the same as the previous rectangular duct. The experimental results indicate that significant global reduction of the radiated tonal fan noise can be achieved.