bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of rough seabed surface on statistics of modal energy flux
Authors: Knobles David P. , Sagers Jason D.
Published: May 2013

When sound propagates through a random media, the wave properties of the acoustic field may be viewed as stochastic variables. It is thus natural to investigate the relationship between the statistical properties of the acoustic field and the random fluctuations of the waveguide. The interest here is a 2-D ocean waveguide with a rough seabed. Numerical solutions to the 2-way integral coupled mode equations (ICME), for random realizations of the roughness from a wavenumber power spectrum, provide the statistics of the modal intensity and cross-mode coherence with range. The roughness induces mode coupling within the trapped spectrum, between the trapped and the continuum spectrum, and to the back propagating modal spectrum. Instead of a master equation for the modal intensities to study the connection between the statistics of the acoustics and the fluctuations in the waveguide as has been advocated in previous studies, the conservation law for acoustic energy flux is used to develop an expression for the individual modal Poynting vectors. In addition to exact numerical computations of the range derivatives of the modal energy flux vectors for both forward and backward propagation, a Poynting vector master equation is derived for the case where the Born approximation is valid.
Rayleigh scattering of sound by spherically symmetric bodies
Authors: Godin Oleg A.
Published: May 2013

An obstacle’s shape is often approximated by a sphere in analyses of sound scattering by air bubbles, objects on or near the seafloor, marine organisms, clouds of suspended particles, etc. Here, an asymptotic technique is developed to study low-frequency sound scattering from spherically symmetric inhomogeneous obstacles. The obstacle can be fluid, solid, or a fluid-filled solid shell. Physical properties of the obstacle are arbitrary piece-wise continuous functions of the distance to its center. The radius of the obstacle is assumed to be small compared to the wavelengths of sound in the surrounding fluid as well as of compressional and shear waves inside the obstacle. General properties of the sound scattering by spherically symmetric bodies are established. Resonant Rayleigh scattering is studied in detail. For plane and spherical incident waves, it is discussed which physical and geometrical parameters of the obstacle can be retrieved from the scattered acoustic field.
Theoretic considerations on how the directivity of a sound source influences the measured impulse response
Authors: Witew Ingo B. , Knüttel Tobias , Vorländer Michael
Published: May 2013

In previous investigations, it has been shown that the directivity of a measurement sound source has a significant influence on the measured room impulse response (RIR). Using a specialized method of analysis, the sources influence can be identified even in the very late part of the RIR even in very reverberant environments. These results seem to be surprising at first and contradict intuitive expectations. In this contribution, the findings are briefly discussed, and the congruence with general room acoustic theory is revised and discussed.
Auditory-tactile music perception
Authors: Merchel Sebastian , Altinsoy M. Ercan
Published: May 2013

The coupled perception of sound and vibration is a well-known phenomenon during live pop or organ concerts. However, even during a symphonic concert in a classical hall, sound can excite perceivable vibrations at the body surface. However, the concert visitor might not be aware of those vibrations, because the tactile percept is integrated with the other senses into one multi-modal percept. This article discusses the influence of whole-body vibrations on the listener experience during the reproduction of concerts recordings. Four sequences were selected from classical and modern music, which include low frequency content (e.g., organ, kettledrum, contrabass). A stimulus length of 1.5 min was chosen in order to provide enough time for habituation. The audio signal was reproduced using a surround setup. Additional seat vibrations have been generated from the audio signal. Test participants were asked to rate the overall quality of the concert experience. The results show that vibrations have a significant influence on our perception of music. This finding is interesting in the context of audio reproduction, but also for the construction of concert venues.
Methods for determining free-swimming positioning and echolocation beam patterns
Authors: Greenhow Danielle , Harley Heidi , Fellner Wendi , Cardwell Adrienne , Mann David
Published: May 2013

Echolocation beam patterns were recorded using a 25-element autonomous, self-contained hydrophone array during free-swimming echoic match tasks. Two GoPro HERO2 cameras mounted at 45-degree angles to the plane of the 4.5 × 4.5 ft PVC array recorded the position of the dolphin during approach and investigation of the sample object presented in front of the array. Using a pre-session calibration file and MaxTRAQ3D software, analysis of video determined exact positioning of the head region during echolocation, including distance from the array and angle to the plane of the array. An LED and ITC-1042 transducer, operated by an Arduino Uno processor board and a Hafler amplifier, were mounted on the array. Simultaneously emitted visual pulses (LED) and acoustic pulse trains were used for synchronization of the acoustic recorders and video cameras. The distinct pulse train was used during post-recording analysis to synchronize the hydrophones using a custom-designed Matlab routine. The hydrophones are sampled at 400 kHz and analyzed in real-time. The maximum and minimum values and time stamps within a 0.32 ms window are stored continuously to reduce the amount of data that needs to be stored. Using the 3-D positioning of the animal, dynamic beam patterns can be reconstructed.
The alignment problem for bat biosonar beampatterns
Authors: Caspers Philip , Pan Rongjiang , Leonessa Alexander , Müller Rolf
Published: May 2013

Unlike the beampatterns of technical acoustical systems, the biosonar beampatterns of bats are highly variable in the shapes of their main- and sidelobes over frequency. Some of this variability could represent adaptations to different sensing tasks. In order to understand such possible adaptations, a quantitative method for the analysis of variability (e.g., principal component analysis) is needed. Since the orientation of biosonar beampatterns is highly variable in-vivo, e.g., due to ear/head movements, and not preserved in isolated noseleaf/ear samples, orientation is left out of the initial analysis. Instead, beampatterns should be aligned to characterize their orientation-independent features. For this purpose, a framework to characterize the beampattern alignment problem and perform the alignment has been drawn up. For each frequency, beampatterns are compared using a distance metric (e.g., a p-norm). By investigating the value of this distance metric over the space of all possible beampattern rotations, it is possible to gain insights into the alignment problem, e.g., with regard to the existence of multiple minima in the metric. This space can also be used to test alignment strategies across multiple frequencies, e.g., through a weighted sum of the respective distances.
Giraffe Helmholtz resonance
Authors: vonMuggenthaler Elizabeth , Bashaw Meredith
Published: May 2013

Many animal species, including elephants and okapi, use sounds above and below the range of human hearing to communicate. A longitudinal study presented here suggests giraffe produce infrasonic vocalizations using Helmholtz resonance. Recordings were made of giraffe (Giraffe camelopardalis) in controlled indoor conditions and naturalistic outdoor conditions. The portable recording and analysis system consisted of a trigger oscilloscope; DAT recorders; Nagra IV-SJ; and computers. Each signal was low-pass/high-pass filtered, and FFT and STFT were performed using PolynesiaTM real-time scrolling analysis. In controlled recordings and in naturalistic situations, two types of signals were identified: audible bursts [(11 Hz (75 dB +/− 3) to 10,500 Hz (80 dB +/− 3)] dominant frequencies between 150 and 200 Hz and covert vocalizations [(14 Hz (60 dB +/− 3) to 250–275 Hz (30 dB +/− 3)] dominant frequencies between 20 and 40 Hz. Both audible and covert signals coincided with neck throw or head toss behaviors. The shape of the giraffe’s respiratory apparatus during this behavior and the frequencies produced implicate Helmholtz resonance as a production mechanism. In naturalistic recordings, two of the five infrasonic vocalizations identified were produced during close range social interactions, suggesting that giraffe use these vocalizations to communicate with con-specifics. The social functions, air and seismic transmission mechanisms of these vocalizations should be further assessed.
An all-optical photoacoustic microscopy system for remote, noncontact characterization of biological tissues
Authors: Sampathkumar Ashwinkumar , Chitnis Parag V. , Silverman Ronald H.
Published: May 2013

Conventional photoacoustic microscopy (PAM) employs light pulses to produce a photoacoustic (PA) effect and detects the resulting acoustic waves using an ultrasound transducer acoustically coupled to the target tissue. The resolution of conventional PAM is limited by the sensitivity and bandwidth of the ultrasound transducer. We have investigated an all-optical, “pump-probe” method employing interferometric detection of the acoustic signals that overcomes limitations of conventional PAM. This method does not require contact with the specimen and provides superior resolution. A 532-nm “pump” laser with a pulse duration of 5 ns excited the PA effect in tissue. Resulting acoustic waves produced surface displacements that were sensed interferometrically with a GHz bandwidth using a 532-nm CW “probe” laser using a Michelson interferometer. The pump and probe beams were coaxially focused using a 50× objective giving a diffraction-limited spot size of 0.5 µm. The phase-encoded probe beam was demodulated using a homodyne interferometer. The detected time-domain signal was time reversed using k-space wave-propagation methods to produce a spatial distribution of photoacoustic sources in the target tissue. Performance was assessed using 3D images of fixed, ex vivo, retina specimens. Apparatus design and imaging results for the all-optical PA system and possible applications will be discussed.
An analysis of the acoustic properties of the cell cycle and apoptosis in MCF-7 cells
Authors: Pasternak Maurice M. , Strohm Eric M. , Kolios Michael C.
Published: May 2013

Through the use of high frequency acoustic microscopy, the acoustic properties of cells through various stages of interphase (G1/G2), mitosis (metaphase, M-phase), and apoptosis were ascertained. The cell thickness, sound velocity, acoustic impedance, density, bulk modulus, and attenuation were determined through a quantitative analysis of the pulse echoes from the cell membrane and substrate using a 375 MHz transducer. Hoechst 33342, Annexin-V, propidium iodide, and FITC-448 Anti-cyclin B1 and D1 mouse antibodies were used to identify cell cycle stage. ANOVA and Tukey post hoc statistical tests were used to quantify differences between cell stages. A total of 174 cells, 58 within each category, were measured. A statistically significant increase in thickness (9.4–11.4 µm), and decrease in attenuation (1.20–1.05 dB/cm/MHz) was observed between G1 and G2 cells, respectively. A statistically significant increase in thickness, and decrease in acoustic impedance, density, bulk modulus, and attenuation was observed between M-phase and G1 or G2. During apoptosis, minor differences were observed between interphase and early apoptosis; however, significant differences in nearly all properties were observed as the cells progressed to late stage apoptosis. The differences found indicate considerable structural and/or organizational alterations occurring as the cell progresses through these phases.
Acoustic and optical characterization of targeted ultrasound contrast agents
Authors: Perez Camilo , Swalwell Jarred , Tu Juan , Chen Hong , Brayman Andrew , Matula Thomas J.
Published: May 2013

We previously developed a flow cytometer system that incorporates the action of ultrasound to characterize shell properties of ultrasound contrast agents (UCA’s). The most recent manifestation involves a flow cytometer modified with a custom square quartz flow cell in place of the standard nozzle and fluid jet. Acoustic coupling to the carrier sheath fluid and UCA samples occurs through a PZT bonded to one side of the flow cell. The PZT-driven UCA oscillations were processed and fitted to the Marmottant UCA model. Shell properties for UCAs (including Definity, Optison, SonoVue, and even homemade bubbles) were determined. A major limitation of the previous work involved a lack of knowledge of the actual acoustic pressure incident on the UCA. The focus of this talk will be on optimization of the pressure inside the flow cell using finite element methods, and the comparison with additional measurements of unpublished data from targeted UCA’s. [Work funded in part by the Life Sciences Discovery Fund #3292512.]
Investigating the effect of fabrication method on the stability and acoustic response of microbubble agents
Authors: Mohamedi Graciela , Hosny Neveen A. , Rademeyer Paul , Park Yoonjee , Owen Joshua , Pham Tuan , Wong Joyce Y. , Kuimova Marina , Stride Eleanor
Published: May 2013

Microbubbles stabilized by a surfactant or polymer coating are already in clinical use as ultrasound imaging contrast agents. They have also been widely investigated as vehicles for drug delivery and gene therapy that can be tracked and triggered using ultrasound. Extensive studies have been made of the effects of the coating material and gas core on microbubble characteristics, but the influence of the fabrication method has received less attention. The aim of this study was to compare the behavior of microbubbles prepared using different techniques. Phospholipid-coated microbubbles were produced using sonication, electrospraying, or in a specially designed microfluidic device. The microbubbles were observed using optical, electron, and fluorescence lifetime imaging microscopy (FLIM) to interrogate their surface microstructure and stability over time. Their acoustic response was then determined in a flow chamber by detecting the pressure scattered from individual microbubbles as they passed through the focal region of a transducer (center frequencies 1, 2.25, and 3.5 MHz; peak negative pressures 50–300 kPa). The method of bubble generation was found to significantly affect the bubble surface characteristics, stability, and acoustic response. The results demonstrate that the processing method affects not only the bubble size distribution but other characteristics important for biomedical applications.
Radiation for bubble contrast agents in inhomogeneous media
Authors: Nguon Chrisna , Denis Max , Chandra Kavitha , Thompson Charles
Published: May 2013

The acoustic field generated by a distribution of micro-bubbles serving as contrast agents for a three-dimensional scattering volume is evaluated. A dual-frequency incident field generated by a confocal transducer insonifies the target and creates a scattered field that includes the difference frequency component that is of interest for improving the resolution in imaging of biological tissue. The scattered pressure is computed for a range of compressibility contrast parameters and wavenumbers using Born series and Padé approximants to ensure convergence as the medium contrast is increased. The effect of this pressure field on the resonant radiation of bubbles is examined, and bubble parameters that influence the amplification of the field measured exterior to the scattering volume are identified. A baseline comparison of the scattered pressure field with and without the presence of bubble contrast agents is presented.
Temporal evolution of subharmonic emissions from a lipid-encapsulated contrast agent
Authors: Shekhar Himanshu , Rychak Joshua J. , Doyley Marvin M.
Published: May 2013

A large body of work has investigated the influence of the excitation pulse, agent size distribution, and the ambient pressure on the subharmonic response of microbubble contrast agents (MCA). The purpose of this study was to investigate the temporal evolution of the subharmonic emissions, i.e., whether the subharmonic response is influenced by the time elapsed since agent constitution. We measured subharmonic emissions from a commercial lipid-encapsulated contrast agent (Targestar-P®, Targeson Inc., San Diego) over the time span of 60 min. The excitation parameters were as follows: 10-MHz frequency, 30–290 kPa pressures, 60 cycles, and 1-kHz pulse repetition frequency. The subharmonic emissions were observed to increase by 11 dB over 60 min relative to those measured immediately after reconstitution. The most striking increase (>8 dB) was observed in the first 15 min. Although we did not observe a change in the agent size distribution, the pressure threshold for subharmonic emissions reduced by nearly two-fold within the time span of our measurements. This work demonstrates that time evolution of subharmonic emissions could bias quantitative estimates obtained from techniques such as subharmonic imaging and subharmonic-aided pressure estimation. Additionally, these findings suggest the possibility for improving subharmonic emission by careful agent design.
Simulations of transcranial passive acoustic mapping with hemispherical sparse arrays using computed tomography-based aberration corrections
Authors: Jones Ryan , O'Reilly Meaghan , Hynynen Kullervo
Published: May 2013

Passive acoustic mapping (PAM) is receiving increasing interest as a method for monitoring focused ultrasound (FUS) therapy. PAM would be beneficial during transcranial cavitation-enhanced FUS treatments, particularly non-thermal, cavitation-mediated applications such as FUS-induced blood–brain barrier disruption or sonothrombolysis, for which no real-time monitoring technique currently exists. However, the use of PAM in the brain is complicated by the presence of the skull bone. If not properly accounted for, skull-induced aberrations of propagating cavitation emissions will lead to image distortion and artifacts upon reconstruction. Through the use of numerical simulations, this study investigated the feasibility of transcranial PAM via hemispherical sparse hydrophone arrays. A multi-layered ray acoustic transcranial ultrasound propagation model based on computed tomography-derived skull morphology was developed. By incorporating skull-specific aberration corrections into a conventional passive beamforming algorithm [Norton and Won, IEEE Trans. Geosci. Remote Sens. 38, 1337–1343 (2000)], simulated acoustic source fields were spatially mapped through digitized human skulls. The effects of array sparsity and receiver element configuration on the formation of passive acoustic maps were examined. Multiple source locations were simulated to determine the imageable volume within the skull cavity. Finally, the reconstruction algorithm's sensitivity to noise was explored.
Passive acoustic mapping of magnetic microbubbles in an in vitro flow model
Authors: Crake Calum , de Saint Victor Marie , Coviello Christian , Owen Joshua , Coussios Constantin-C , Stride Eleanor
Published: May 2013

Magnetic microbubbles can be successfully retained near a vascular target and simultaneously imaged using conventional B-mode ultrasound. When further modified to carry a drug, they could enable significant enhancements in targeted drug delivery for applications such as sonothrombolysis, where stable cavitation has been shown to play a key role. However, the effect of the increased proximity of the microbubbles under the effect of the magnetic field on their acoustic response remains unknown. Passive acoustic mapping is a method that enables real-time spatiotemporal monitoring of cavitation dynamics in an arbitrary plane or volume within the field of view of the ultrasound probe, and classification of the type of cavitation activity on the basis of the spatial distribution of frequency-domain emissions. In the present work, PAM is used to investigate the effect of bubble proximity and flow rate on the type, sustainability, intensity, and spatial distribution of cavitation activity observed for both magnetic and non-magnetic microbubbles excited by 0.5 MHz therapeutic ultrasound in an in vitro flow model. It is hoped that this study will not only yield a new method for real-time monitoring of drug delivery using magnetically trapped microbubbles, but will also help elucidate complex bubble–bubble interactions in therapeutic ultrasound fields.
Industrial fan noise control using flow obstructions
Authors: Oddo Remy , Gérard Anthony , Pearson Michel , Amyotte Adrien , Masson Patrice , Sgard Franck , Berry Alain
Published: May 2013

Fans are used in a lot of industrial processes and are sometimes a source of important noise for workers. The first aim of this study was to identify some problematic fans in Québec industries, for which the noise exposure exceeds the CSST (Comission de la santé et sécurité au travail) limit of 90 dBA for 8 h. We have focused on fans having a high tonal content, for which the Simple Silence technology can be applied, i.e., tonal fan noise control using obstructions in the flow. Two analytical models of the tonal noise radiated by these fans have been proposed: a free field model based on the Lowson model and an in-duct model based on the Goldstein model. The first free-field model has been applied to the control of the noise from a series of eight evaporator fans, having a strong blade passage frequency (BPF) tone at 90 Hz. These fans have been controlled in-situ, in a cold storage room, using trapezoidal obstructions in the downstream flow field of the fans. The second in-duct model has been applied to control the tonal noise from an in-duct air-extractor fan used in the underground gold mining galleries. Several obstructions have been tested in the upstream flow field.
Analyzing the impact of the inlet temperature on the acoustic noise production form a supersonic jet using large eddy simulations
Authors: Semlitsch Bernhard , Mihaescu Mihai , Fuchs Laszlo , Gutmark Ephraim
Published: May 2013

Non-ideal expanded supersonic jets emerging from a convergent-divergent nozzle produce three different types of noise, i.e., the shock-associated broadband noise, the screech noise, and the turbulent mixing noise. Interesting to note that the screech tone outside of the nozzle was exposed mostly in downscaled laboratory experiments, while under realistic conditions the exhaust jet of a gas turbine engine does not show this phenomena. Apart from a geometric scaling difference, usually a lower temperature is employed in experimental studies. It is believed that the screech tone occurs due to self-excitation of the shear-layer in a feedback-loop. Acoustic waves generated by vortical structures interacting with a shock are propagating upstream within the subsonic region of the shear-layer or outside of it. They eventually hit the nozzle's lip and excite instabilities at a certain frequency. The compressible Navier-Stokes equations are simulated numerically by using Large Eddy Simulation approach. The effect of supersonic jet operation temperature onto the associated noise is investigated. The jet-exit Mach-number is 1.56, while the total temperature ratios considered at the inlet plane of the nozzle are 1.27, 2.05, and 3.65. The differences in the near-field acoustics will be presented in each of the cases and the flow-acoustic interaction will be analyzed and quantified.
Upgrade of a multi-channel active noise control system for an industrial stack
Authors: Boudreault Louis-Alexis , L'Espérance André , Boudreau Alex
Published: May 2013

Active noise control has been studied in the 1990s as an innovative way to reduce the noise in specific situations. Some applications are well known today and found commercial success like noise-canceling headphones. However, the use of active noise control in industrial applications is more complex, thus being an uncommon solution in this field. The use of active noise control for industrial stack noise is one of these applications. One of the first large-scale implementation has been set up at the end of the 1990s. This system was a 10-channel active noise control system installed on a 1.8 m wide chimney to attenuate a 320 Hz pure tone. At that time, an 8 dB noise reduction was achieved at error microphones. Fifteen years later, it has been decided to upgrade the system with the latest generation of digital signal processor (DSP) allowing a real-time optimization and better tracking speed. This paper describes the overall system and the updated multi-channel active noise controller developed for this application. It also presents the improvements, the achieved noise reduction, and the associated environmental benefits.
On the spatial distributions for randomly spaced arrays
Authors: Au Jenny , Thompson Charles
Published: May 2013

In this work, we examine the statistical characteristics of the randomly spaced transducer arrays. Approaches to realizing the linear and two-dimensional arrays are considered. The array elements are equally weighted in amplitude and their contribution to received signal is by virtue of adjustment by their spatial location. The cumulative distribution for the number of transducers as a function of transducer spacing and its relationship to the spatial objective function is given. The case for Dolph–Chebychev objective function is shown in detail and in closed-form. The statistical effect spatial binning of transducer elements is examined.
Influence of nonlinear parameters in Mirror filter to compensation performance of nonlinear distortions
Authors: Uesako Natsuki , Kajikawa Yoshinobu
Published: May 2013

Mirror filter is used for the compensation of nonlinear distortions for electro-dynamic loudspeaker systems and is based on the nonlinear differential equations. The design of Mirror filter requires the estimated parameters of a target loudspeaker system. If you obtain the corresponding parameters of a target loudspeaker system and arrange Mirror filter designed using those parameters in front of the loudspeaker, then the nonlinear distortions can be compensated. Hence, the estimated parameters are very important to achieve high compensation performance. In this paper, we therefore examine the effects of the estimated parameters to the compensation performance. Concretely, we clarify the effects by varying each nonlinear parameter in Mirror filter. Simulation and experimental results demonstrate that the compensation performance for the second order nonlinear distortions depends on a nonlinear parameter of the force factor in loudspeaker systems.
A new loudspeaker for low frequency radiation by linear motion type piezoelectric ultrasonic actuators
Authors: Saito Hiroya , Negishi Hirokazu , Ohga Juro , Oohira Ikuo , Maeda Kazuaki , Oishi Kunio
Published: May 2013

The authors had proposed new direct-radiator loudspeaker constructions with a conventional paper cone radiator driven by ultrasonic motors (USM), as a substitution for voice-coil motor. However, those models needed a revolution to linear motion conversion mechanism, and avoiding zero region non-linearity, like class A amplifier. These complications came from the conventional USM, since it is a rotational and having zero region non-linearity inherently. Here, the authors would propose a new mechanism by using new ultrasonic linear actuators, called longitudinal-bending multilayered transducers with independent electrodes (LBMTIE). The beauty of LBMTIE is linear and to control vertical motion and horizontal motion independently, hence zero region non-linearity avoided. Therefore, it is possible to substitute the voice-coil motor directly, which avoids the complicated mechanisms mentioned above. In this LBMTIE driven loudspeaker, vertical movement voltage be fixed and horizontal voltage is driven by audio signal, like voice-coil motor. In addition, there is a big contrast against conventional voice-coil motor, which is a typical transducer, as its electrical input and sound pressure output are direct proportion each other. This is because LBMTIE driven loudspeaker may behave a sort of modulator, which is not direct proportion in between input electric power and output sound pressure level.
Saxophone modeling and system identification
Authors: Smyth Tamara , Rouhipour Marjan
Published: May 2013

In this work, saxophone instrument frequency responses are estimated at both the mouthpiece corresponding to the input impedance and outside the bell, using acoustic measurement and post signal processing. The measurement technique is based on one previously developed for measuring the acoustic properties of instrument bells but is adapted to account for the fact that the saxophone bell does not easily separate from the instrument bore and must be measured as a single unit. Furthermore, measurements are taken of the instrument configured with all possible fingerings covering the playable range of the B-flat tenor saxophone, and instrument reflection and transmission functions are estimated for, and applied to a waveguide model of, each tone-hole configuration. Having the instrument frequency responses at both the mouthpiece and the bell for every possible fingering allows for an improved parametric synthesis, but also allows for saxophone system identification, inverse modeling, and estimation of player-instrument control parameters during real-time performance.
Perception and production of complex bowing movements in violin performance
Authors: Schoonderwaldt Erwin , Demoucron Matthias , Altenmüller Eckart , Leman Marc
Published: May 2013

In bowed-string instruments, the primary function of bowing movements is to control the parameters that govern the stick-slip interaction between the bow and the string, giving the performer control of the sound. Not less importantly, bowing movements have to be planned ahead in order to anticipate future events. In fast, repetitive bowing movements involving string crossings and bow changes the primary and anticipatory movements become integrated, forming an overall, in the simplest case circular movement pattern. The relative timing of string crossings and bow changes is an inherent property of the shape of these patterns, which therefore has an important influence on the quality of the note transitions. We will present two complementary studies that provide insight in this coordination phenomenon. A perceptual study has been conducted using a virtual violin, in which the participants could influence the relative timing between string crossings and bow changes by a simple slider, giving insight in the perception of such transitions and typical temporal constraints. Analyses of bowing movements show in detail how the coordination is realized in performance, and how the performer adapts her/his movement patterns to performance constraints, such as tempo and dynamic level.
Time-domain simulation of the bowed cello string: Dual-polarization effect
Authors: Mansour Hossein , Woodhouse Jim , Scavone Gary P.
Published: May 2013

A detailed time-domain simulation is implemented to model the bowed cello string. Building on earlier simulation models, several new features have been added to make the model more realistic: in particular, both polarizations of the string motion are included, as well as the longitudinal vibrations of the bow hair. These additional features can be turned on and off in the model to evaluate their relative importance. In all previous simulations, the bow-hair was assumed stiff enough to suppress any motion of the string perpendicular to the bowing direction. High-speed video recordings, on the contrary, have suggested that the amplitude of this motion is not negligible compared to the motion of the string in the bowing direction. The major source of this motion is tracked down to the X-Y coupling through the bridge. Although this extra dimension of vibration may not necessarily contribute much to the radiated sound by itself, it can modulate the effective bow force and hence affect the stick-slip motion of the string. The longitudinal vibration of the bowhair is also included in our model. The compliance of the bow-hair was accounted for in previous studies in a crude way, but without enough detail to capture the difference between different bows.
Analysis/synthesis of bowing control applied to violin sound rendering via physical models
Authors: Maestre Esteban
Published: May 2013

A prominent challenge in instrumental sound synthesis is to reproduce the expressive nuances naturally conveyed by a musician when controlling a musical instrument. Despite the flexibility offered by physical modeling synthesis, appropriately mapping score annotations to sound synthesis controls still remains an interesting research problem, especially for the case of excitation-continuous instruments. Here we present our work on modeling bowing control in violin performance, and its application to sound synthesis via physical models. Minimally invasive sensing techniques allow for accurate acquisition of relevant timber-related bowing control parameter signals. The temporal contours of bowing control parameters (bow velocity, bow force, and bow–bridge distance) are represented as sequences of low-order polynomial curves. A database of parametric representations of real performance data is used to construct a generative model able to synthesize bowing controls from an annotated score. Synthetic bowing controls are then used to render realistic performances by driving a violin physical model.
Differences in technique and sound in beginner and expert cello performances and use of acoustic information to provide support for performance techniques
Authors: Sato Taichi , Miyagawa Shoichi , Yamatani Hiromi
Published: May 2013

We studied the differences in performance between beginners and expert musicians by taking cello performance as the object of our research. By principal component analysis of the beginning part of a performance—the part when a performer just begins to play—we were able to distinguish between performances by beginners and those by experts. We showed that the process of mastery of an instrument, in which the sound of a beginning performer becomes better, can be evaluated using principal component analysis. We studied the characteristics of the ability to skillfully draw the bow across the cello strings, and we created acoustic information based on these characteristics. By giving this acoustic information to beginners, the beginners learned to become almost as skillful as expert cellists in their ability to draw the bow skillfully across the strings, even though they were only beginners.
Sensorial substitution system from vision to audition using transparent digital earplugs
Authors: Lescal Damien , Rouat Jean , Voix Jérémie
Published: May 2013

Since the Tactile Vision Substitution System (TVSS) developed by Bach-Y-Rita in 1960’s, several sensorial substitution systems have been developed. In general, the so-called “sensorial substitution” system transform stimuli characteristic of one sensory modality (for example, vision) into stimuli of another sensory modality (for example, audition). These systems are developed to help handicapped persons. We developed a sensorial substitution system from vision to audition. An artificial neural network is used to identify the important parts in the image. The virtual acoustic space technic is used to generate localizable sounds. A sound is associated to each important parts of the image. The entire real-time system has been implemented on iOS platforms (IPhone/IPad/IPod Touch). We associated our system with transparent digital earplugs. This way the user is aware of the audio scene happening around him. The system has been tested on non-blind persons and the results are presented.
An active hearing protection device for musicians
Authors: Bernier Antoine , Voix Jérémie
Published: May 2013

Professional musicians have to deal with two great problems when wearing hearing protection devices (HPDs): the occlusion effect and the isolation effect. The occlusion effect is an unnatural and annoying perception of one’s own voice when wearing HPDs. It will affect all musicians whose instrument induces vibrations to the skull, including a singer's vocal tracts and instruments mechanically coupled to the head, such as a trumpet or a violin. The isolation effect is the unnatural sensation of being isolated from a given sound environment. It is caused by a non-uniform attenuation of the HPD over the frequency spectrum and the absence of compensation for psychoacoustic factors, such as uneven loudness perception. These two effects cause a shift of perception between the musician's perception and the audience's perception and therefore compromise the musician’s ability to offer a good performance to his audience. This paper presents the design and implementation of an active musician’s HPD featuring a feedback active noise control system for occlusion effect reduction as well as psychoacoustic compensations for isolation effect reduction. The proposed test procedure and preliminary performance assessments are presented to validate both the test procedure and the system for future subjects trials on a larger scale.
Improved hearing conservation in industry: More efficient implementation of distortion product otoacoustic emissions for accurate hearing status monitoring
Authors: Bockstael Annelies , Keppler Hannah , Botteldooren Dick
Published: May 2013

Preventing occupational hearing damage requires close monitoring of workers' hearing. Implementing Distortion Product Otoacoustic Emissions (DPOAEs) in-field is a sensitive and feasible approach provided that a combination of minimal measuring time and infrequent false-positives—i.e., cases where elevated background compromises DPOAEs—is found. This paper investigates how measurement time can be reduced by carefully selecting the tested frequency span and resolution, and how false-positives are minimized by comparing DPOAEs acquired in noise with DPOAEs previously obtained in optimal test conditions. To test this, DPOAEs have been registered with a 1/8-octave band resolution from 841 Hz to 8 kHz for 60 subjects, in quiet conditions and in white noise levels ranging from 54 dB(A) to 90 dB(A). Measurement accuracy is confronted to decrease the measurement time as a function of frequency resolution and range. Diagnostic importance and sensitivity to background noise is addressed for different frequency regions. Within-subject variation of DPOAEs in noisy conditions is assessed both between different noise conditions and between subsequent probe placement. Obtained test–retest statistics quantify normal variability and allow within normal working routines to select for further investigation persons with DPOAEs falling outside this range.
Do recent findings on jet noise answer aspects of the Schultz curve?
Authors: Downing Micah , Gee Kent , McInerny Sally Anne , Neilsen Tracianne , James Michael
Published: May 2013

Recent research efforts on nonlinear propagation from high performance jet aircraft have revealed an interesting challenge to predicting community response. This challenge focuses on receiver perception of these unique acoustical signals, which contain acoustical shocks that appear to increase their relative loudness and/or noisiness. This current finding suggests a need for an improved description of a receiver perception of the loudness of these signals in order to improve the assessment of noise impacts from these aircraft. Looking backwards, an interesting question emerges: did the earlier low bypass jet engines on commercial and transport aircraft also include these acoustical shocks? If they did contain these features, then the perceptual differences observed between aircraft and other transportation noise sources may be partially explained.
Rail noise and vibration in Australia—A case study
Authors: Chavand Vincent
Published: May 2013

This paper reviews the various stages of a major rail project undertaken in New South Wales (NSW), Australia, between 2010 and 2012. This case study involves 40 km of new track adjacent to existing railway lines in the Hunter Valley, NSW. The project is located within a mixture of rural and urban settings and had the potential to impact on a large number of sensitive receivers during both the construction and operational phases. The project approvals required compliance with a number of relatively new noise and vibration guidelines and policies, which provides an opportunity for the author to reflect on the recent evolutions in noise and vibration control practices and policing in Australia. This paper reviews the project from the approvals process to its commissioning phase from a noise and vibration point of view. It explores the construction and operational noise modeling methodologies, reviews the design process and adopted mitigation measures and, in doing so, it discusses the practical challenges met through the course of the works.
Noise control for rooftop chiller units: An application in Istanbul
Authors: Meredith David , Dilmen Hakan , Çay Merve , Belek H. Temel , Arisoy Ahmet
Published: May 2013

A telecommunication corporation located in Gayrettepe, Istanbul, installed 20 rooftop chillers on their six-story building to air condition their newly introduced client Internet server hall in spring 2010, causing annoyance in the mostly residential neighborhood during the summer months. After a series of night-time acoustic measurements were performed to characterize the noise emitted by the chillers, a three-dimensional noise model of the area was created. Using this model, a ventilated noise control barrier was designed to bring down the contribution of the chiller units to the overall environmental noise level. Following the manufacturing and installation of the barrier, a series of night-time measurements were performed anew, which demonstrated that the application has mitigated the contribution of the noise emitted by the rooftop units to within regulation limits.
Numerical modeling for analyzing microfluidic acoustophoretic motion of cells and particles with application to identification of vibro-acoustic properties
Authors: Liu Zhongzheng , Wang Han , Han Arum , Kim Yong-Joe
Published: May 2013

Microfluidic, acoustophoretic cell/particle separation has gained significant interest recently. In order to analyze the motion of cells/particles in the acoustophoretic separation, a one-dimensional (1-D) analytical model in a “static” fluid medium has been widely used, while the effects of acoustic streaming, viscous boundary layers, and 2-D and 3-D geometries are usually not considered. Therefore, it is not sufficient to accurately predict the cell/particle motion. Thus, a numerical modeling procedure for analyzing the acoustophoretic cell/particle motion is presented to include the aforementioned effects. Here, the first-order acoustic pressure and the second-order acoustic streaming velocity are first calculated by using a high-order finite difference method. Then, acoustophoretic force is calculated based on the acoustophoretic force equation proposed by Gorkov and is applied to the Newton’s equation of motion to calculate the motion of cells/particles. Through various simulations, the effects of acoustic streaming on the motion of cells/particles are studied. Since the acoustophoretic motion depends on the vibro-acoustic properties (e.g., density, compressibility, and size) of particles/cells, the vibro-acoustic properties can be estimated by optimally fitting the experimental and simulated trajectories. The properties obtained from experimental results with polystyrene beads show good agreement with the data reported in literature.
Macro-scale acoustophoretic separation of lipid particles from red blood cells
Authors: Dutra Brian P. , Rust Michael , Kennedy Daniel , Masi Louis , Lipkens Bart
Published: May 2013

Autologous blood salvage is frequently used in cardiac surgery. However, shed mediastinal blood contains lipid particles ranging in size from 10 to 60 μm. Lipid emboli flow subsequently lodge in the brain capillaries resulting in strokes, leading to neurocognitive dysfunction and death. A novel acoustophoretic filtration system has been developed to separate the lipids from the red blood cells (RBCs). The system works at the macro-scale, supporting flow rates in excess of 2 L/h. The system is designed such that the acoustic radiation force is able to overcome the combined effects of fluid drag and buoyancy forces. Both RBCs and lipid particles are therefore trapped in the ultrasonic standing wave. Due to the opposite contrast factors of lipids and RBCs, the two components separate at opposite nodes within the standing wave, with lipids concentrating at pressure anti-nodes and RBCs at pressure nodes. Subsequent gravitational separation is used to separate the lipids and RBCs. Preliminary results were obtained with a suspension of 10x diluted bovine blood mixed with a 0.75% safflower oil emulsion. Measurements indicate a 15 fold increase in hematocrit of the captured RBCs when compared to the original sample solution, and an excellent separation of the oil droplets.
Toward optimal functional representation of head-related transfer functions in the horizontal plane
Authors: Zhang Wen , Abhayapala Thushara D. , Kennedy Rodney A. , Zhang Mengqiu
Published: May 2013

Head-related transfer function (HRTF) individualization using principle component analysis (PCA) modeling rely on the empirical data to reduce HRTF dimensionality for an optimal representation and to achieve HRTF personalization by tuning the model weights with the subject anthropometric parameters. However, for these representations, the basis is discrete and data dependent, which can limit its usefulness in universal HRTF representation. This paper studies the optimal functional representation of magnitude HRTF of 45 subjects for sound sources in the horizontal plane. We first use circular harmonics to extract the subject-independent HRTF angular dependence. The remaining spectral components of 45 subjects are then modeled by PCA and two standard functions, i.e., Fourier series and Fourier Bessel series. The metric to evaluate the model efficiency is the expansion weights cumulative variance. We identify that individual magnitude HRTFs over 20 kHz range could be modeled adequately well by a linear combination of only 19 Fourier series; this is a near optimal representation in comparison with the statistical PCA model. Further analysis of the model weights with subjective anthropometric measurements will provide a promising method for HRTF individualization, especially considering the nature of data independent continuous basis functions employed in the proposed functional representation.