bluuebunny/crossref_metadata_2025 huggingface dataset:
Subharmonic imaging for vasa vasorum
Authors: Faez Telli , de Jong Nico
Published: April 2012

It is known that vasa vasorum plays an important role in atherosclerotic plaque pathogenesis and stability. Recent advances in contrast-enhanced ultrasound have shown that this technique can be used to characterize the carotid vasa vasorum and intra-plaque angiogenesis. Ultrasound propagating through tissue is nonlinear and contains higher harmonics of the transmitted wave, but it does not contain energy at the subharmonic frequency, which revives a strong interest in subharmonic emissions (backscattered energy at half the transmit frequency) from contrast agents. Subharmonic imaging (SHI) has potentially a larger contrast to tissue ratio compared to other imaging methods and has already been used in clinical experimental studies. In this study, the subharmonic scattering of phospholipid-coated contrast agents in the frequency range preferred for carotid imaging (5-15 MHz) is investigated optically and acoustically and in vitro and in vivo. The results of the measurements indicate that: -The subharmonic scattering of the microbubbles is sufficiently detectable (−10 dB below the fundamental) at 10 MHz at low acoustic pressures of 100 kPa. -The subharmonic response of microbubbles can be dynamically manipulated using a 2.5 kHz pressure wave. In conclusion, SHI has a great potential to be exploited for carotid imaging.
High frequency subharmonic imaging: practical implementations and recent developments
Authors: Needles Andrew , Daeichin Verya , Bosch Hans , de Jong Nico , van der Steen AFW , Foster F. Stuart
Published: April 2012

High-frequency ultrasound systems have been developed to provide appropriate imaging resolution for small anatomical structures. Typical applications include small animal preclinical research as well as intravascular ultrasound (IVUS) in larger animals and humans. In addition to traditional B-Mode (structural) and Doppler (functional) imaging, contrast detection modes have been implemented on these systems to improve the sensitivity to microbubbles in the microcirculation. This talk will overview some examples of these implementations and their respective advantages and disadvantages. Examples include direct radio frequency (RF) filtering and pulse sequence approaches, on both single element and array based systems. Additionally, subharmonic imaging will be compared to other harmonic detection approaches (namely nonlinear fundamental and second harmonic) and cases where subharmonic only detection is optimal at high frequencies. Recent advances explore the use of the self-demodulation phenomena to enhance to contribution of the subharmonic signal from microbubbles and improve detection. Examples of in vivo data from mice and rats will be shown, illustrating the ability to detect changes in blood perfusion by analyzing contrast uptake over time with curve fitting algorithms. Finally, the detection of microbubbles targeted to endothelial cells, using subharmonic imaging in small animals, will be demonstrated.
Band structures of Lamb waves in one-dimensional piezoelectric composite plates: polarizations and boundary conditions
Authors: Zou Xin-Ye , Cheng Jian-Chun
Published: April 2012

Theoretical studies are presented for the band structures of Lamb waves in a one-dimensional phononic crystal plate consisting of piezoelectric ceramics placed periodically in an epoxy substrate. The band structures for different polarizations and electric boundary conditions are calculated for the composite plates in this paper. It is found that the first band gap is always broadened by polarizing piezoelectric ceramics, and the band gap widths with short circuit boundary condition are always larger than that with open circuit situation for the same polarization. Employing harmonic frequency analysis, the numerical results show that the Lamb wave modes corresponding to certain frequencies in the composite plates can be modulated by the different electric boundary conditions. The researches show that it is possible to control the Lamb waves in the composite plates in the engineering according to need by choosing suitable polarizations and electric boundary conditions.
Environmental noise situation in Bangkok
Authors: Lertsawat Krittika , Kovudhikulrungsri Lalin , Phoolsawat Surocha , Suksaard Tanaphan
Published: April 2012

The overview of the environmental noise management policy and regulations will be briefly discussed in this presentation, including the problem analysis on the noise management issue in Bangkok. All of the applicable policies and regulations related to environmental noise issues in Bangkok were only dominated by the road traffic noise sources. The environmental noise situation in Bangkok will be illustrated and discussed in this presentation, seeking the comparative discussion from the international experts and practitioners for the better determination methods and technologies, applied for the future policies and regulations.
Sound propagation along a long partial enclosure
Authors: Chu S. H. K.
Published: April 2012

The acoustical properties of sound in a long rectangular partial enclosure with various opening sizes and positions are investigated numerically in the present study. The finite element method is adopted to estimate the mode shapes across the cross section of the partial enclosure inside a free field environment. Some acoustic modes with patterns similar to some of the rigid-wall duct modes are found. The sound propagates in form of modes inside the partial enclosures as in the rigid-wall duct case. The long partial enclosure leaks sound and the opening radiates sound into a free space in the numerical model. The sound radiation is associated with the interactions between acoustic mode shape of the partial enclosure, opening size and position. Results indicate that the behaviour of acoustic pressure radiated from the opening is a significant effect on the resonance frequencies.
Application of Geographic Information Systems (GIS) and related techniques for the management and control of noise in various urban structures and cultures
Authors: Kang Jian
Published: April 2012

This paper explores possibilities and potentials of integrating Geographic Information Systems (GIS), noise mapping and other related techniques for the management and control of noise in various urban structures and cultures. This includes the use of noise maps and GIS information in examining the relationships between environmental noise and social-economic factors; comparison of noise resistance of different urban structures based on micro- and macro-scale sound propagation models; effects of building arrangements in a given urban area based on genetic algorithms; and the development from urban noise maps to urban sound maps and urban soundscape maps, taking perception and cultural factors into account.
Current visual interfaces for acoustical modeling analysis
Authors: Dorsch Dana
Published: April 2012

With the development of advanced noise mapping software, consultants have the ability to present their clients with graphic depictions of sound level distribution in a given area. Most noise mapping software interfaces easily with Auto CAD and Google Earth, where GIS data formats can be imported and exported based on a coordinate system specified by the user. The merging of these technologies can be especially useful where the study site is located in a complex terrain or urban area. This paper describes several case studies where the development of noise maps has been improved from a basic diagram of noise contours lines to a complex, three dimensional imagery of terrain and buildings that can be rendered in Google Earth.
Correlation between oscillations and translational motion of droplets induced by surface acoustic waves: towards low power actuators
Authors: Michael Baudoin , Philippe Brunet , Olivier Bou Matar , Adrien Bussonière
Published: April 2012

Actuators based on SAW are versatile tools to achieve, atomization, jetting, oscillations, or inner mixing of droplets. Basically, acoustic waves are generated at the surface of a piezoelectric substrate by a transducer consisting of interdigitated fingers. The acoustic energy is then transmitted to the drop whose motion is induced by nonlinear acoustical effects (acoustic streaming, radiation pressure). However, an increase of the temperature occurs inside the drop due to the dissipation of acoustic energy. This could be harmful for the manipulation of biofluids. In this presentation, we will show that the amount of energy required to move or deform droplets can be drastically reduced by exciting them at their eigen frequencies. We will also exhibit and explain the correlation existing between the droplets amplitude of oscillation and their translation speed.
Microbubble acoustic surface cleaning
Authors: Versluis Michel
Published: April 2012

Surface cleaning is accomplished by fluid mechanical forcing, often assisted by chemical and acoustical activation. Examples include the removal of nanoparticles from IC semiconductor substrates and the disruption of bacterial biofilms in dentistry. The presence of bubbles is known to greatly enhance the cleaning efficiency as it promotes mixing of the chemicals and it yields higher stresses through acoustic streaming and jetting following asymmetric collapse of the bubbles. With smaller nanofabricated structures and more delicate surgical therapies, there is a growing demand for precision cleaning with minimum damage to the surrounding media. Here we explore the concept of micro-machined cylindrical pits acting as cavitation nuclei for a continuous source of microbubbles, thereby localizing the cavitation phenomena and suppressing its inherent chaotic nature. The micropit bubble was found to be stable against dissolution, and the resonance behavior of surface mode vibrations of the cap was modeled with the unsteady Stokes equation combined with a Fourier-Bessel expansion. Above a pressure threshold, destabilization of the micromeniscus results in bubble pinch-off which was studied using high-speed imaging down to nanoseconds timescales. It was also found that the acoustic coupling and merging of cavitation clouds from neighboring micropits increasingly promote acoustic surface cleaning.
Acoustic microstreaming induced by pattern of Faraday waves on a bubble wall
Authors: Maksimov Alexey , Leighton Timothy , Birkin Peter
Published: April 2012

Interest to acoustic microstreaming is supported by the variety of applications: micromixing, transferring lipid vesicles and large molecules in desired direction, and selective particle trapping which are essential to the success of lab-on-a-chip- devices. It is generally assumed that the main contributions to the streaming generated by a gas bubble come from the pulsation and translation modes. This study deals with the microstreaming which is induced when a bubble is driven acoustically in the regime of parametrically generation of Faraday waves. The greater wall displacement amplitude for l > 1modes means that their effect on the flux of species near the bubble wall can be much greater than that of the breathing mode. The modes with a fixed order l have a high degree of degeneracy equal to (2l+1). The choice of which modes are chosen to grow to steady state, and which are selected out, determines the shape of the perturbation and hence the structures of the streaming flow. Basic features of pattern formation on the bubble wall have been recently derived by Maksimov & Leighton (doi:10.1098/rspa.2011.0366) which provides determination of streaming structures. These theoretical findings are used to interpret the experiments on selective particle trapping by oscillating microbubble.
30 MHz driven fluid mixing in paper-based microfluidic systems
Authors: R. Rezk Amgad , Qi Aisha , R. Friend James , Ho Li Wai , Y. Yeo Leslie
Published: April 2012

Paper-based microfluidics have recently become a topic of interest due to the ease and low expense in fabrication, especially compared to traditional microfluidics fabrication materials, making them suitable for inexpensive diagnostics. We report a convective actuation mechanism in a simple paper-based microfluidic device using surface acoustic waves to drive mixing. Using a Y-channel structure patterned onto paper, the mixing induced by 30 MHz acoustic waves is shown to be consistent and rapid, overcoming several limitations associated with its capillary-driven passive mixing counterpart: the latter exhibits nonuniform and irreproducible mixing. Capillary-driven mixing offers only poor control, is strongly dependent on the paper's texture and fibre alignment, and permits backflow, all due to the scale of the fibres being significant in comparison to the microfluidics features. Using a novel hue-based colourimetric technique, the mixing speed and efficiency is computed. For the acoustically driven mixing the effects of changing the input power, channel tortuousity and fibre/flow alignment was assessed. The hue-based technique offers several advantages over grayscale pixel intensity analysis techniques in facilitating quantification without limitations on the colour and contrast of the samples, and can be used, for example, for quantification in on-chip immunochromatographic assays.
Programmable manipulation of microbubbles in microfluidic systems with surface acoustic wave
Authors: Meng Long , Cai Feiyan , Niu Lili , Li Yanming , Zheng Hairong
Published: April 2012

Programmable microfluidic systems for bioparticles manipulation that could enable automated biological analysis and diagnostics have the potential to revolutionize a wide range of applications in life sciences research, clinical diagnostics, and drug discovery. Several methods such as those based on hydrodynamic force, magnetic tweezers, and dielectrophoresis can manipulate the movement of the bioparticles successfully. However, these methods must be constructed the flow structure, magnetic wire, and electrode in the microchannel respectively, which not only limits the flexibility of manipulation but also makes the sample more likely to be contaminated. In this paper, a programmable microfluidic device is developed to manipulate the microbubbles along an arbitrary trajectory in the microchannel without any structure by introducing phase-shifts to a planar standing surface acoustic wave field. The microbubbles can be transported in a square trajectory, circular trajectory and even helix trajectory via adjusting the relative phase between the excitation signals controlled by LabVIEW program. The results reveal that the microbubbles can be transported over a predetermined distance continuously until they reach the targeted locations. This acoustic programmable microfluidic device would have potential applications on drug screening, cell studies, and other biomedical applications.
Effect of degraded binaural cues in cochlear implant users and normal hearing listeners on spatial release from masking
Authors: Litovsky Ruth , Goupell Matthew , Kan Alan , Misurelli Sara , Stoelb Corey
Published: April 2012

Bilateral cochlear implants (BiCIs) are being provided to a growing number of individuals with bilateral severe-profound hearing loss and are becoming standard in many clinics worldwide, to restore spatial hearing skills and improve speech understanding in noisy environments. While patients generally perform better with BiCIs, their performance is significantly worse than that of normal hearing (NH) listeners. Spatial release from masking (SRM) in NH listeners depends on monaural (head shadow) and binaural cues. In BiCI users, SRM appears to be primarily due to head shadow; however, binaural-mediated SRM is weak or absent. Two factors are most likely responsible for this. First, bilateral CI processors are not coordinated, rendering binaural cues weak, absent or inconsistent. Second, patients' history with auditory deprivation likely results in poor neural survival at numerous cochlear locations. Our studies suggest that signal processing tools can be applied to bilateral CI users to restore binaural sensitivity. In this talk, data will be presented from studies with adults and children, in free field and using binaural research processors. Results from studies on restoration of interaural level and timing differences to BiCI users will be discussed in the context of what is needed for binaural SRM restoration. Work supported by NIH-NIDCD (grants 5R01DC003083 and 5R01DC8365)
Prediction of speech masking release for fluctuating interferers based on the envelope power signal-to-noise ratio
Authors: Jørgensen Søren , Dau Torsten
Published: April 2012

The speech-based envelope power spectrum model (sEPSM) presented by Jo/ rgensen and Dau [(2011). J. Acoust. Soc. Am. 130, 1475-1487] estimates the envelope signal-to-noise ratio (SNRenv) after modulation-frequency selective processing, which accurately predicts the speech intelligibility for normal-hearing listeners in conditions with additive stationary noise, reverberation, and nonlinear processing with spectral subtraction. The latter condition represents a case in which the standardized speech intelligibility index and speech transmission index fail. However, the sEPSM is limited to conditions with stationary interferers due to the long-term estimation of the envelope power and cannot account for the well known phenomenon of speech masking release. Here, a short-term version of the sEPSM is presented, estimating the envelope SNR in 10-ms time frames. Predictions obtained with the short-term sEPSM are compared to data from Kjems et al. [(2009). J. Acoust. Soc. Am. 126 (3), 1415-1426] where speech is mixed with four different interferers, including speech-shaped noise, bottle noise, car noise, and a highly non-stationary cafe noise. The model accounts well for the differences in intelligibility observed for the stationary and non-stationary interferers, demonstrating further that the envelope SNR is crucial for speech comprehension.
Vibration analysis of beams with arbitrary elastic boundary conditions excited by a moving mass
Authors: Lv Binglin , Li Wanyou , Zhou Haijun , Du JIngtao
Published: April 2012

In this paper, one newly developed method named the Improved Fourier Series method is applied to the vibration of a beam elastically supported at the both end excited by a moving mass. The flexural displacement of the beam is supposed to be one set of Fourier Series coupled with several appended terms. Based on the energy principle, the mass and stiffness matrix of the beam system are obtained. The mass is added to the model with its gravitation treated as the excitation to the dynamic system. In the end, the effect of the moving mass to the vibration of the beam is analyzed.
Investigation of active vibration isolation with inertial actuators
Authors: Shi Hui
Published: April 2012

A single stage active vibration isolation system with inertial actuators is presented in this paper. The system frequency responses were obtained from the finite element model of the vibration isolation system. By using curve fitting method, the transfer functions of primary paths and secondary paths were derived, which were defined as transfer functions from excitation forces to error sensors and from secondary forces to error sensors respectively. Then multi-input multi-output active vibration control simulation and experiment were conducted in the Lab. The results show that good vibration attenuations were achieved. Some conclusions were given and discussed at last. Key words: vibration isolation; inertial actuator; multi-input multi-output; active control
Tuned viscoelastic damper for hollow shaft's torsional vibration control
Authors: Duan Yong , Wu Wenwei
Published: April 2012

This paper presents a piece of work on hollow shaft vibration control using viscoelastic materials in torsional directions. Columned viscoelastic damper is designed as a capsule containing viscoelastic material and elastic material, the outer layer of the capsule is viscoelastic material, the inner layer is elastic material. The damper is mounted somehow into the void of the shaft. When the shaft is vibrating, the damper can provide damping for the passive control of torsional vibrations. The viscoelastic damper is designed based on the principle of dynamic absorber in theoretically. When the damper has been designed, the frequency response functions of the damping system include damper and shaft can be calculated by solving the dynamic equations, then, the damping effect of the viscoelastic damper on the hollow shaft can be obtained. It's shown that the damping effect depends on the loss factor of the viscoelastic material, and the damper can provide large damping for the hollow shaft when the loss factor of the viscoelastic material achieves its optimal value. And these conclusions can also be obtained by ANSYS software.
Vibration isolation performance of isolated slab track
Authors: Ho Wilson , Wong Banting , Chu Isaac , Kong Calvin , Kwan Richard
Published: April 2012

Isolated slab tracks (IST) have been used in a number of existing railway lines in Hong Kong to reduce viaduct re-radiated noise and groundborne noise. The design has adopted both profiled-type and full-space elastomeric mat, placed underneath the concrete track slab to reduce trackform vibration transmission to the supporting structure. The profiled-type mat was installed on the Tseung Kwan O line while a full-space mat on the Lok Ma Chau line in Hong Kong. This paper presents the latest vibration measurement results of the full-space elastomeric mat IST and compares the vibration isolation performance with other resilient trackform types. The advantages and disadvantages of using profiled mat IST and full-space mat IST are discussed from the view angle of trackform engineers and acousticians.
Acoustic properties of Turkish voiceless fricatives
Authors: Ertan Esra , Kopkallı Yavuz Handan
Published: April 2012

The investigation of acoustic parameters which differentiate place of articulation for fricatives has been limited to few languages. This study investigates the acoustic properties of Turkish voiceless fricatives representing three different places of articulation, /f, s, ∫/. For each fricative, spectral properties, duration, overall amplitude, F2 transition, and center of gravity were measured. Each fricative occurred in different vowel environments, in one and two word syllables and in different positions within a word. The participants were 6 (3 male, 3 female) native Turkish speakers. A total of 4320 tokens were analyzed. The findings showed that frequency range, spectral peak location, F2 transition and center of gravity are cues to place of articulation in Turkish. The findings showed that the frequency range is 1500-10500 Hz for /f/, 3500-10800 Hz for /s/, 1800-9400 Hz for /∫/. The spectral peak location measurements were; /s/ > /f/ > /∫/. The mean duration of fricatives were /∫/ >/s/ >/f/. The amplitude for fricatives are as follows; / ∫/ >/s/> /f/. The onset of F2 transition were; /∫/ >/s/> /f/ and the center of gravity measurements were; /s/ > /∫/ > /f/.
Motion of apical and laminal /s/ in normal and post-glossectomy speakers
Authors: Reichard Rachel , Stone Maureen , Woo Jonghye , Murano Emi Z , Prince Jerry L
Published: April 2012

There are two ways to produce an `s' in English: apical and laminal. They are almost identical perceptually and the reason for choosing one type is not well understood. This study questions whether one type is preferred in certain conditions, such as high vs low palate height or in post surgical tongue adaptation. This study examines palate height, and motion of critical and non-critical tongue regions in 8 normal speakers and 8 post-glossectomy patients who have had surgical resection of squamous cell carcinomas of the tongue. Speech was recorded with tagged-MRI and processed to track displacement and velocity of 2-D midsagittal tongue tissue points in the tongue tip and body during the utterance of the word “a souk”. Results indicate that subject category had a greater effect on s motion than palate height. Both critical and non-critical articulators in subjects with apical s used higher velocity and displacement on average than subjects with laminal s. Compared to patients with larger resections, patients with smaller resections had larger velocities and displacements in both tongue areas suggesting less debility. The single patient with flap reconstruction showed the highest velocity and greatest displacement, suggesting a different type of articulatory compensation. This research was supported in part by NIH R01 CA133015
The effects of jaw surgery on bilingual speech
Authors: Mishler Alan , Chang Charles
Published: April 2012

Surgery designed to correct misalignments of the jaw may lead to changes in the fine phonetic detail of speech segments. In some cases, these changes are unstable, with the acoustic parameters of post-surgical speech gradually reverting toward pre-surgical values, even when this causes speech to become less perceptually or acoustically “normal” (Lee et al, 2002; Niemi et al, 2006). This process might be driven primarily by tactile feedback, which could have differential effects on consonants and vowels, since consonants involve greater contact between articulators; alternatively, it might be driven primarily by auditory feedback, which might be expected to affect consonants and vowels to a similar degree. Previous studies have examined only vowels or consonants in isolation, and they have examined only a single language at a time. Here, a case study of a Korean-English bilingual's speech over the course of a year before and after surgery is presented. The subject's entire phoneme inventory in both languages is examined in order to determine the effects of surgery on different segment types and to determine to what extent the effects are language-specific.
Temporal structure in the speech of persons with Dementia of the Alzheimer's Type (DAT)
Authors: Carozza Linda , Cantor Pamela , Quinn Margaret , Bell-Berti Fredericka
Published: April 2012

Although cognitive and language processes in dementia have been studied extensively, the question of motor speech degeneration in the course of dementing illness is a relatively unexplored area. The potential for early dissociation of motor functions of language at the level of speech production has not been explored; an interaction between motor speech and language production and perception changes should inform our understanding of the deterioration in dementia. In previous reports on two persons with DAT, we have shown inconsistent final lengthening and effects of syllable-final consonant voicing on vowel duration for one of the two speakers. We recorded one of the speakers again, and his speech was markedly slower. In this report, we expand our analysis to include three additional persons with mild-to-moderate DAT, from whom a series of 4-word phrases containing a target word occurring in phrase-medial or phrase final position was elicited. We will present the results of our analysis of final lengthening, compensatory shortening, and the effects of final consonant voicing on vowel duration.
Time reversal mirror localization technology based on a high-resolution MVDR algorithm
Authors: Yuan Yan-yi , Sheng Xue-li , Ling Qing , Lu Jia , Bai Ye , Jiang Mei-ren
Published: April 2012

Minimum variance distortionless response (MVDR) algorithm has broken through the Rayleigh limit restrictions and makes higher resolutions possible. However, they are easily affected by complex underwater acoustic environments and are not sufficiently robust, so it is difficult to use them in real underwater systems. Time reversal mirror technology is a new method of localization, which may be effectively applied to target detection and localization. To improve its robustness, the MVDR algorithm is combined with time reversal mirroring for passive detection and location. This method makes full use of underwater multipath channel information and reduces the effects of complex underwater environments. The performance of time-reversal MVDR that is based on fixed diagonal loading and robust capon beamforming (RCB) was also studied. Simulations, water tank experiment and sea trial proved it is feasible and practical Keywords: MVDR; time reversal mirror; robust capon beamforming; passive location
Array signal Processing for noise control and signal separation based on time-reversal and impulse response
Authors: Hsieh Yu-Hao , Too Gee-Pinn
Published: April 2012

Noise control and signal separation are important purposes for acoustic signal processing. This study presents a detailed analysis for designing an acoustic signal processing procedure based on time-reversal method, which has been widely used for capable to compensate distortion due to multipath effect. However, setting transducers to retransmit at source places is impracticable for some applications. A way to overcome such limitation is to model wave propagation path between two points using impulse response function. Adaptive digital filter, deconvolution with singular value decomposition and Tikhonov regularization, and correlation function, are chosen to calculate impulse response function. All three different techniques above are tested in details with various array properties. The conclusion is made according to the level of accuracy using signal-to-noise ratio and correlation coefficient as indicators, and the computation time under the same controlled parameters as well.
Prediction of acoustical parameters for open plan offices according to ISO 3382-3
Authors: Rindel Jens Holger
Published: April 2012

In the new international standard ISO 3382-3 the measurement procedure for open plan offices is described and a number of new room acoustical parameters for the objective evaluation are defined. Among the new parameters are the privacy distance and the distraction distance, both derived from the STI (speech transmission index) as a function of distance from the sound source. The final evaluation is a balanced compromise between a number of parameters that depend on the amount of sound absorption, the application of screens between work stations and the level of background noise. With room acoustic simulation software these measurements can be simulated, thus providing a tool for the acoustical design of open plan offices. The paper presents an example office with a range of alternative acoustical solutions that include different amount of absorption, screens of different height, and different levels of background noise. Also the influence of dynamic background noise from people talking can be taken into account, leading to a shorter privacy distance. This provides a background for the discussion of the efficiency of various acoustical measures in open plan office design.
Head-mounted active noise control system and its application to reducing MRI noise
Authors: Miyazaki Nobuhiro , Kajikawa Yoshinobu
Published: April 2012

We propose an active noise control (ANC) system for reducing periodic noise generated in a high magnetic field such as noise generated from magnetic resonance imaging (MRI) devices (MRI noise). The proposed ANC system utilizes optical microphones and piezoelectric loudspeakers and consists of a head-mounted structure to control noise near the user's ears. Moreover, internal model control (IMC)-based feedback ANC is employed because the MRI noise includes some periodic components and is predictable. Our experimental results demonstrate that the proposed ANC system (head-mounted structure) can significantly reduce MRI noise by approximately 30 dB in a high field in an actual MRI room even if the imaging mode changes frequently.
The role of paying attention to sounds in soundscape perception
Authors: Botteldooren Dick , Boes Michiel , Oldoni Damiano , De Coensel Bert
Published: April 2012

It has been stated frequently that the soundscape as perceived and appraised by the user of a space, extends beyond the physical stimulus. We argue that, when introducing to human-factor in analyzing a sonic environment, the sounds that people hear play an important role. This holds in particular for rather quiet and infrequent disturbance of park soundscapes. Auditory attention mechanisms are essential in the process. Attention can be drawn by saliency elements such as changes in time and frequency, but it can also be outward oriented and voluntary. These mechanisms could explain the special role of natural sounds in distracting attention from mechanical background hum in a park environment. These theoretical concepts have now been implemented in measuring equipment that allows estimating how often particular sounds will be heard by a human listener. The methodology includes biologically inspired feature extraction, learning based on co-occurrence of features and saliency, attention focusing, and inhibition of return. Extension to binaural measurements increasing the unmasking effect is also discussed.
From noise control to sound design: the class room as a soundscape project
Authors: Bauer Juergen
Published: April 2012

As part of an overall campus building project, the Department of Architecture in Waterford Institute of Technology in Ireland moved to provisional premises in autumn 2011, in a city centre former warehouse, dating from 1875. While this building is a fine example of historic industrial architecture which was previously used successfully as a museum, as a school venue it is “acoustically seen” inappropriate. The studios are more halls rather than rooms and have an approx. height of 5 meters; two classes share one unit and are subdivided by screens, with lectures and tutorials needing to be scheduled at different times in order to avoid (acoustic) clashes. Most surfaces are hard, and in some cases, the class units are even exposed to open galleries and circulation areas. How can the noise problem be transformed into a soundscape project? How can the current situation be used to develop sound as a design tool that informs the awareness about sound phenomena, strengthen the understanding of sound mitigation and instill the confidence to design it? This paper investigates different approaches as to how to introduce sound as a design tool in early architectural education and summarizes the learning outcomes from using the class room as a sound design lab.
Nearly Perfectly Matched Layer (NPML) absorbing boundary condition for elastic waves propagation in solid
Authors: Li YiFeng , Bou Matar Olivier , Bao YaPing
Published: April 2012

In this work, a method named Nearly Perfectly Matched Layer (NPML) using a Complex Frequency Shift (CFS) stretched-coordinate metrics is presented to extend the Perfectly Matched Layer (PML) to simulate elastic wave propagation in solid media. This non-physical layer is used at the computational edge of a Discontinuous Galerkin Finite Element Method (DG-FEM) algorithm and a Pseudo-Spectral (PS) algorithm in time domain, as an Absorbing Boundary Condition (ABC) to truncate unbounded media. The main advantages of NPML is linked to the facts that (a) the obtained system of equations has the same form exactly as the original system of equations and so strongly hyperbolic, and (b) the introduced NPML variables are updated by Ordinary Differential Equations (ODE) in place of Partial Differential Equations (PDE) in classical PML implementation. Numerical results show that the NPML has the same ability of energy absorption as the Convolutional Perfectly Matched Layer (CPML) for attenuating the outgoing waves, moreover, it facilitates implementation in the DG-FEM scheme than CPML and preserves the highly parallelisable capabilities of this numerical scheme.
Distant-talking speech enhancement based on spectrum restoring with phoneme labels
Authors: Kakino Naoto , Hukumori Takahiro , Morise Masanori , Nishiura Takanobu
Published: April 2012

With the development of communication and speech recognition technology, remote conference and robot communication systems have been developed in recent years. Although these are valid in close-talking speech, distant-talking speech degrades the performance of the systems. The reason is that it is affected by energy decay, noise and reverberations depending on the distances. To solve this problem, many noise reduction and speech enhancement approaches have been proposed. In the conventional approaches, the example-based speech enhancement is one of the effective noise reduction methods in distant-talking conditions. The most similar example of noisy speech to input signal is detected from model examples of clean and noisy speech signals. Thereby it can estimate and suppress the noise based on the clean speech. Although it can effectively reduce noise, it is not clear the performance in the distant-talking speech condition with the decay of speech energy. Thus in this paper, we proposed a distant-talking speech enhancement based on spectrum restoring with phoneme labels. It restores the clean spectrum from decayed spectrum based on spectrum envelopes for each phoneme label. We demonstrate the experiment to evaluate the effectiveness of proposed method. As a result, we confirmed that it can effectively enhance the target speech.
The waveguide invariant
β
and bottom reflection phase-shift parameter P
Authors: Shang Erchang , Wu Jinrong , Zhao Zhendong
Published: April 2012

It is known that the waveguide invariant β is affected by the shallow-water environment. In this paper the effect due to bottom sediment is investigated. It is found that the effect of sediment bottom can be concentrated on one parameter P – the bottom reflection phase shift parameter. For a Pekeris waveguide, under WKB approximation, a very simple analytic relation is given: β≈1+P/(k0Heff), here Heff is the `effective depth', and Heff =H+P/2k0. It is shown that the value of β related to different high-speed sediments (including layered sediment) is ranged in 1.0 and 1.5. Some numerical examples including the layered sediment case are conducted to verify this result. Good agreement between the results calculated by KRAKEN and by WKB with parameter P has been found. The advantage of using parameter P is that it can cover any type of high-speed sediment even including shear wave effect, moreover, it also works for layered sediment provided using P(o/mega) instead of constant P. Hence, by using parameter P allows us to have a model-free platform to investigate the sound field in shallow-water including the bottom effect on the waveguide invariant β. [This work was supported by NSFC under Grant No.10874201 and No.11074271]
Time-reversal focusing stability in the presence of background internal waves in shallow water
Authors: Petnikov Valeriy , Lunkov Andrey
Published: April 2012

Effect of background internal waves on spatial and temporal low frequency sound focusing stability is investigated for an open oceanic shelf by means of numerical simulations. Focusing is achieved with the time-reversal procedure at a single source-receiving element at 10km range. Calculations are performed in terms of normal mode coupling theory. Internal wave field modeling is carried out using an averaged experimental power spectrum of vertical thermocline displacements measured in the Shallow Water'06 experiment. The results of numerical experiments show that the focal spot is stable for about 1 hour in the presence of typical internal waves on an open shelf. Two adaptive time-reversal algorithms are proposed to increase this period up to 12 hour. [Work supported by RFBR 11-02-00779.]
Does listener weighting of binaural cues take advantage of the binaural statistics of reverberant environments?
Authors: Stecker G Christopher , Brown Andrew D
Published: April 2012

A series of experiments quantified listeners' weighting of auditory spatial information conveyed by interaural differences of time (ITD) and level (ILD) across cue type (ITD-ILD “trading”) and over the durations of brief sounds (“temporal weighting”). Results demonstrated the dominance of cues, especially ITD, carried by the onsets of rapidly modulated or continuous tones. Whereas post-onset ITD information received little weight for such sounds, post-onset ILD was more influential, especially near sound offset [Stecker and Brown, JASA 127:3092-103. 2010]. As a consequence, the relative weighting of ITD and ILD changes systematically with modulation rate, with greater weighting of ILD in cases where post-onset ITD is unavailable [Stecker, Hear. Res. 268:202-12. 2010]. Greater weighting of post-onset ILD than ITD is consistent with observations of dramatic ITD distortion by echoes [Rakerd and Hartmann, JASA 78:524-33. 1985] and of a greater role for ILD in dynamic aspects of the precedence effect [Krumbholz and Nobbe, JASA 112:654-63. 2002] resulting from changes in the acoustic environment. Evidence regarding temporal weighting of ITD and ILD will be reviewed and compared to the statistics of binaural cue values across a variety of reverberant recordings. [Supported by NIH R03-DC009482, R01-DC011548, F31-DC010543, T32-DC000033]
Using time-varying loudness to model the reverberance of rooms
Authors: Cabrera Densil , Lee Doheon , Martens William L.
Published: April 2012

The reverberant decay of sound over time is one of the most perceptually salient features of reverberation in rooms. This paper examines the concept that the perception of reverberation decay can be modelled using dynamic loudness. As well as being a plausible application of time-varying loudness modelling, this approach helps to explain why higher sound pressure level stimuli are more reverberant than otherwise identical reverberant stimuli – because the slope of the loudness decay function depends on the stimulus level. Loudness decay parameters are derived in analogy to conventional reverberation parameters (reverberation time and early decay time), which provide a better match to subjective experimental data concerned with: impulsive, running, and overall reverberance; and using artificial and measured room impulse responses.
Anatomical changes in the inner ear of the bullfrog across metamorphic development
Authors: Alexander Erika E. , Tarr Andrew M. , Simmons Andrea M.
Published: April 2012

Metamorphic development in the bullfrog, Rana catesbeiana, is characterized by widespread changes in peripheral transduction pathways and in the auditory brainstem, in preparation for the transition from a fully aquatic to a semi-terrestrial existence. The time course of development of the inner ear organs has not been as extensively examined. A combination of immunohistochemical, cresyl violet and trichrome staining to were used to delineate the development of the saccule, an otolith organ sensitive to particle motion and to seismic stimuli, across metamorphosis. From early embryonic to metamorphic climax stages and extending to the froglet period, the saccule increases linearly in area, correlated with the growth in body size. Myosin VI label indicates that hair cell density in the central region of the saccule remains relatively stable in tadpoles, but then decreases between froglet and subadult stages. From these results, it is hypothesized that hair cell proliferation occurs more extensively in tadpoles than in froglets.
Variation in the songs of humpback whales (Megaptera novaeangliae) wintering in the Northwestern and Main Hawaiian Islands
Authors: Chen Jessica , Lammers Marc , Au Whitlow
Published: April 2012

A study of the humpback whale song in the Northwestern Hawaiian Islands (NWHI) and the Main Hawaiian Islands (MHI) during the 2009 season suggests that humpback whale song may be more variable than previously suggested. Data from five autonomous acoustic recorders deployed at locations in the NWHI and MHI were analyzed to compare the frequency of occurrence of song units by whales in the island chain. There appears to be a gradient of differences in song units throughout the Hawaiian Island chain, rather than the previously assumed, more discrete differences between breeding populations. Recordings from each site were randomly selected. Song units were classified as one of 23 units and counted to compare between sites. Changes in the frequency of occurrence in a few of the most abundant units suggest a gradual change throughout the island chain. However, this may be confounded by changes that occur throughout the season throughout the ocean basin. Further work examining the amount of variation both between and within humpback whale breeding populations should be conducted.
Assessment of soft and mineralized tissue formation in a rat bone healing model using quantitative ultrasound (QUS)
Authors: Rohrbach Daniel , Hesse Bernhard , Preininger Bernd , Perka Carsten , Raum Kay
Published: April 2012

It is hypothesized that QUS is a promising candidate for the assessment of early stages of bone healing. 5-MHz QUS measurements in through transmission mode were conducted in vitro on a 2-mm osteotomy rat model (N=10). 2D parametric QUS images of speed of sound (SOS), ultrasound attenuation (UA), and broadband UA (BUA) were registered to histology sections and to projections obtained from 3D μ-CT images. Based on histology two groups of healing (N(A)=5: early healing stage and N(B)=5: early reparative phase) were defined. Parameter variations (medians and integrals) evaluated within the osteotomy gap region were compared between the healing groups. ANOVA revealed significantly higher attenuation and SOS values in group B (UA(A)=14.5±4.5 dB, UA(B)=35±10.1 dB, F=18.5; BUA(A)=4.09±1.7 dB/MHz, BUA(B)=9.6±4.4 dB/MHz, F=6.8; SOS(A)=1543±9 m/s, SOS(B)=1590±34 m/s, F=8.7). ROC analysis with AUC values between 0.84 and 1 confirm a good predictive power of US parameters. The bone mineral density (BMD) based variance assessed from μCT was less pronounced (F=9.5). Moderate correlations of UA and SOS with BMD were observed (R2<0.7). These results demonstrate that ultrasound parameter variations are sensitive to tissue alterations that are not depicted by BMD, but coincide with cartilage formation in the early reparative phase.
Modeling ultrasound interaction with cancellous bone: investigation on the nature of the two compressional waves
Authors: Mézière Fabien , Muller Marie , Bossy Emmanuel , Derode Arnaud
Published: April 2012

Although ultrasound might be useful to assess bone quality, the mechanisms of ultrasound propagation in trabecular bone are still poorly understood. For example the propagation of a short pulse that leads, under some conditions, to two transmitted longitudinal waves, a fast and a slow one, is not well explained yet. The objective of this work is to further investigate the nature of these two longitudinal waves in simplified bone model media. The approach is to determine if the fast wave could result from a guided propagation in the solid matrix, the slow wave being due to the propagation in the surrounding fluid (bone marrow). In this context, we study the propagation of the coherent waves through simplified and customizable binary structures, obtained by a random addition of scatterers, with characteristic dimensions, material properties and anisotropy similar to those of bone. The benefit of such simplified structures is that ultrasound propagation in the entire medium can be theoretically studied from the properties of a single scatterer.
New designs of air-coupled ultrasonic transducers using micro-stereolithography
Authors: Hutchins David , Billson Duncan , Leigh Simon , Pursell Chris
Published: April 2012

Micro-stereolithography, a form of high resolution rapid prototyping, has been used to design and construct novel designs of ultrasonic transducers for use in air. This approach allows for designs to be available that are difficult to produce by other means. The work will describe experiments that have been conducted with capacitive devices in two configurations: planar devices that are based on capacitive micromachined ultrasonic transducers (CMUTs), and those with a spiral geometry backplate for the generation of modified wavefronts. In addition, the fabrication technique has also been used to make structurally-modified materials (so-called metamaterials) to change the emitted characteristics in air. Examples are given of the type of applications for which these ultrasonic transducers could possibly be used.