bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and theoretical investigation of self-sustained vibration in a two-layer vocal fold model with left-right stiffness asymmetry
Authors: Zhang Zhaoyan , Luu Trung Hieu
Published: April 2012

The vibratory characteristics of a self-oscillating two-layer vocal fold model with left-right asymmetry in body-layer stiffness were experimentally investigated, with the goal of better understanding the relative difference in vibration amplitude and phase between the two folds. Two regimes of distinct vibratory pattern were identified. In the first regime with extremely large stiffness mismatch (larger than a factor of ten), vocal fold vibration was dominated by the vibration of the soft fold only, while the other fold was enslaved to vibrate at the same frequency. The fundamental frequency was close to that of the soft fold in a symmetrical condition. In the second regime when the left-right stiffness mismatch was reduced, both folds vibrated with comparable amplitude. In this regime, either fold can exhibit a relatively larger amplitude but the stiff fold consistently led the soft fold in phase for all conditions. The experimental results were compared to predictions from a two-dimensional plane-strain vocal fold model, and qualitatively good agreement was obtained between experiment and simulation. The clinical implications of the results of this study are also discussed. [Work supported by NIH.]
Properties of the duration of English rhythm segments
Authors: Nakamura Shizuka
Published: April 2012

The properties of the duration of English rhythm segments, which comprised a set of stressed and unstressed syllables, were investigated. The speech sounds of short sentences, each including three to five stressed syllables, spoken by 20 native speakers were used. The following definitions of the rhythm segment were adopted for comparative judgment: a stressed syllable and succeeding weak syllable sequence; preceding weak syllable sequence and a stressed syllable; a stressed syllable and a half of preceding and succeeding weak syllable sequences; and the interval between adjacent stressed syllables. The measurement based on the detailed acoustical analysis showed that the duration of each segment by the native speakers was distributed around a peak at about 0.7 second, which was considered to be a target rhythmic period. Some segments, which include the secondary stressed syllables, were distributed separately around a half of the target period. However, they could not be put closer to the main distribution, by exchanging the secondary stressed syllable for the primary one or weak syllable. For the universal description of the rhythm structure, the duration of the rhythm segment was approximated by a series of the target periods into which a half period was interpolated irregularly.
Model-based geoacoustic inversion
Authors: Gerstoft Peter
Published: April 2012

The unknown geoacoustic environment often limits sonar-processing performance. Thus, there is a need for better estimates of the geoacoustic parameters. From the start of geoacoustic inversion more than two decades ago this has been model-based. Advanced propagation codes are based on ray tracing, wavenumber integration, normal modes or parabolic equations. The environment model is parameterized using ocean sound-speed and sediment sound-speed, density and attenuation. In some cases range-dependent models has been used. Initially classical least squares were used. But early on stochastic optimization methods as simulated annealing and genetic algorithms became popular. Understanding of uncertainties is important for the development of the methods. A major effort has been addressed using Bayesian methods and Markov chain Monte Carlo methods. Uncertainties are used to find the most important parameters and the obtained geoacoustic inversion uncertainties can be mapped into sonar performance assessment. In a typical experimental scenario, the data arrives sequentially and new improved estimates can be obtained by updating previous estimates at significantly less computational expense than if each data observation were treated independently. Current efforts are focused on model-based geoacoustic inversion sequentially using sequential methods such as particle filters or Kalman-family of filters.
Group modes based time reversal imaging algorithms for pipeline inspection using ultrasonic guided waves
Authors: Li Weichang , Liu Shuntao , Song Limin
Published: April 2012

This paper presents a time reversal imaging technique utilizing a group of guided wave modes over a broad frequency band. This increases both the bandwidth integrated power and the mode diversity of the propagating wave. Typically, dispersion is minimized by selecting a single mode. Instead, we develop algorithms to coherently combine the group of modes to obtain increased signal to noise ratio and sensitivity, and we compensate for dispersion using time reversal to improve image quality and extend the inspection range. Imaging is computed via an efficient angular spectrum propagation algorithm without numerically computing the Greens functions. The performance improvement is demonstrated via signal processing results based on numerically simulated data.
A maximal mutual information based feature selection method in sound classification
Authors: Fan Xueli , Feng Haihong
Published: April 2012

In sound classification problem, a feature selection method based on improved maximum mutual information is proposed. Better sound classification performance is expected with smaller computational effort by evaluating the “information content” of classification features, only selecting the relevant features of a classifying system, and excluding redundant ones. The proposed method is based on a “greedy” selection of the classification features. The mutual information is measured based on both the output class and the selected features. Simulation experiment was carried out to evaluate performance of sound classification with the proposed feature selection method. The selected features were feed into neural network for sound classification. The classification accuracy was compared with the mutual information feature selector (MIFS). Experimental results showed that the proposed method can produce better sound classification than the classical method. This work has been sponsored by Jiaxing Engineering Center, Institute of Acoustics, Chinese Academy of Sciences and Jiaxing Earelectric Co., Ltd.
Wavefront statistics from measurements made in the Philippine Sea and comparisons to path integral theory
Authors: Chandrayadula Tarun K. , Colosi John A. , Worcester Peter F. , Dzieciuch Matthew
Published: April 2012

Between April 2010 and April 2011, acoustic transmissions were carried out by six sources moored near the sound channel axis and, which were deployed across a 200-300 km radius in the Philippine Sea. The acoustic sources transmitted broadband chirp signals that spanned frequency bands ranging from 140-200~Hz to 200-300~Hz. The transmissions were recorded by a water column spanning Distributed Vertical Line Array (DVLA) that was placed roughly at the center of the area covered by the sources. The transmission ranges from the different sources to the DVLA varied from 125~km to 450~km. The Philippine Sea is an oceanographically diverse environment, which apart from internal waves also contains energetic eddies and internal tides. The acoustic data recorded by the spatially diverse array is hence an opportunity to quantify the degree of anisotropy in the acoustic propagation. This presentation first discusses the wavefront resolution capabilities of the DVLA. The receptions are then used to estimate narrowband ray statistics such as, mean intensity, scintillation index and, depth coherence. Apart from the narrowband statistics, broadband wavefront statistics such as pulse time spread, frequency coherence and pulse time wander are also estimated. The wavefront statistics for the different propagation paths at the array are contrasted with each other and then compared with predictions from path integral theory.
Theoretical fluctuation predictions for low-frequency acoustical propagation ranges of 25 to 107 km in the 2009-2010 Philippine Sea experiment
Authors: Andrew Rex , White Andrew , Mercer James , Worcester Peter , Dzieciuch Matthew , Colosi John
Published: April 2012

Short range propagation experiments in deep water provide volume-only weak scattering paths that can be used to test the limits of validity of fluctuation theories for low-frequency acoustical signals. Colosi et al [J. Acoust. Soc. Am., 126, 1069-1083, 2009] suggested that Munk-Zachariasen theory (which uses first-order Rytov theory modified for the ocean environment) may be applicable in these cases; they used it to predict statistics for a 75-Hz signal propagated over a range of 87 km in the eastern North Pacific. Several scenarios used in the Philippine Sea experiments involving wideband signals may fall into this category: in 2009, ranges of 45 and 107 km were used (transmitter and receivers in the main sound channel) with carrier frequencies 82 and 284 Hz, and in 2010, continuous ranges from 25 to 43 km using a 61 Hz carrier (transmitter at 150 m and receivers near full ocean depth.) Predictions for all scenarios are presented, and comparisons are made against statistics observed for the 2009 107 km path. [Work supported by ONR.]
Modeling uncertainty in transmission loss due to spatio-temporal variation in environmental parameters
Authors: Bissinger Brett E. , Becker Kyle M.
Published: April 2012

Tactical prediction and decision aid tools require acoustic propagation modeling. The effectiveness of these tools relies on knowledge of the transfer function between model inputs - either measured or predicted - and model outputs. Of particular interest is this transfer when inputs are uncertain and characterized statistically. The Recognized Environmental Picture experiment 2011 (REP11) was designed to provide observations of spatio-temporal variability in oceanographic and acoustic quantities. REP11 was comprised of multiple runs of co-located and contemporaneous oceanographic and acoustic measurements repeated over twenty-four hours. Acoustic measurements were made using a broad-band source towed along radials from a fixed receiver array. The sound speed field in the water column was sampled independently during each run using gliders, towed instruments, and moorings, each having a different spatio-temporal resolution. Due to the nature of the ocean environment, the sound speed field varied both in time and space for each traversal of the track, yielding a suite of realizations representing the sensitivity of acoustic pressure to spatio-temporal variations in the environment. Based on these data, the statistics of transmission loss from propagation simulations using the observed sound speed fields are compared to the statistics of the measured acoustic pressure fields.
Reverberation modeling with transport theory
Authors: Thorsos Eric I. , Yang Jie , Elam W. T. , Henyey Frank S.
Published: April 2012

Transport theory has been developed for modeling shallow water propagation at mid frequencies (1-10 kHz) where forward scattering from a rough sea surface is taken into account in a computationally efficient manner. The method is based on a decomposition of the field in terms of unperturbed modes, and forward scattering at the sea surface leads to mode coupling that is treated with perturbation theory. Transport theory has recently been extended to model shallow water reverberation, including the effect of forward scattering from the sea surface. Transport theory results will be compared with other solutions for reverberation examples taken from ONR Reverberation Modeling Workshop problems. These comparisons show the importance of properly accounting for multiple forward scattering in shallow water reverberation modeling. [Work supported by ONR Ocean Acoustics.]
Acoustical design of the National Theatre Company of China (NTCC)
Authors: Huang Chan Chun , Qin You Guo , Yan Xiang , Wang Peng
Published: April 2012

The National Theatre Company of China seats 886, volume 5,400 m3, and reverberation time is 1.2s without audience and orchestra. As part of the design process, measurements on CAD computer and acoustical simulation using Raynoise software and full-sized materials samples were conducted over two year period. The hall in plan is bell shape. The ceiling is a curved cloud, with its U-shape balcony above the main floor (stall), two side rails provide the useful early reflections to the central rear seating area. The unique wall architectural features around the auditorium was analyzed on the models that all interior surfaces combine to distribute sources on the stage uniformly over the seating areas and to yield optimum values for reverberation time—RT, early decay time—EDT, Lateral fraction—LF, and strength—G.
Acoustical design of the new concert hall at Helsinki Music Centre, Helsinki, Finland
Authors: Oguchi Keiji , Komoda Motoo , Hakozaki Ayako , Quiquerez Marc , Toyota Yasuhisa
Published: April 2012

The Helsinki Music Centre opened in Helsinki, Finland on August 31, 2011. The Music Centre is anchored by the 1,704-seat concert hall, and is supported by 6 small halls, each with a different program, and the Sibelius Academy, the premier conservatory in Finland. The concert hall is the new home for Finland's two major orchestras, the Finnish Radio Symphony Orchestra and the Helsinki Philharmonic Orchestra. The concert hall is configured in the vineyard style with terraced steps in the auditorium, and measures 35m wide, 48m long and 20m tall. To support the stage acoustics, a 12m diameter ensemble reflector is suspended at a height of approximately 15m above the stage. The stage acoustics are also enhanced by motorized orchestra risers. The acoustical design and characteristics of the Concert Hall are reported.
Factor analysis of reverberation perception
Authors: Meng Zihou , Dai Lu
Published: April 2012

The reverberation perception in a concert hall is affected by many attributes although the reverberation time may be the most important. To study the contribution to the perceived reverberation from different attributes, a series of listening tests are carried out. The semantic meaning of the reverberation is studied with the questionary to audio engineers and architectural acoustician. The factors to be analyzed are selected based on this semantic study. The subjects are asked to judge the running reverberation impression caused by acoustic scenes simulated by measured or virtual room impulse responses. The reverberation time of the room impulses used in the tests to stimulate the sound field are from 0.5 to 6.0 seconds. Besides the reverberation time, the attributes taken into the consideration in the factor analysis include the clarity, the sound level, the energy ration of early to late reflection, the distance between the source and listener, the volume and shape of the room and also the content of the sound. Based on the result of the factor analysis, a functional expression is proposed to describe the relationship between the perceived reverberation and a group of attributes.
Effects of water levels on distribution patterns of the Yangtze finless porpoises in Poyang and Dongting Lakes, China
Authors: Wang Kexiong , Dong Lijun , Akamatsu Tomonari , Kimura Satoko , Wang Shiyong , Mei Zhigang , Li Songhai , Wang Ding
Published: April 2012

Two large freshwater lakes in China (Poyang and Dongting Lakes) are crucial habitats of the Yangtze finless porpoises. The lakes are confronted with threatens from low water levels. For evaluating possible impacts of low water levels on the porpoises in the lakes, the distribution patterns of the animals in the lakes were monitored in different seasons by using a boat-towing A-tag array from 2009 through 2011. The survey routes were almost same among different seasons. The acoustical detection number (i.e. encounter number) of porpoise in every 3-km section was calculated by counting the bearing angle traces of the sonar sources recorded by the array. The numbers in the same section were compared between high and low water level periods. Results indicated that porpoises appeared to congregate in deep water areas in low water level periods, while they tended to disperse toward the near shore waters in high water level periods. The results suggest concentration of individuals during low water level period. The variations of distribution patterns in different water level periods remind us that protection efforts should be focused on different areas according to the changes of water levels in different seasons.
Multi-dimensional real-time blood flow velocity field measurement in elastic vascular phantoms using ultrasonic particle image velocimetry technique
Authors: Song Ruibo , Qian Ming , Niu Lili , Jin Qiaofeng , Zheng Hairong
Published: April 2012

The experiment was implemented to measure the multi-component blood flow velocity in elastic vascular phantoms. Poly (vinyl alcohol) cryogel, PVA-C, is presented as a tissue-mimicking material, suitable for application in ultrasound imaging. The hardness of PVA-C changed with the number of freeze-thaw cycles. Two kinds of PVA phantoms with different shape were made in our experiment. Mechanical tests were performed on cylindrical samples with a pressure column, and Young's modulus were obtained varying from 50kPa to 320kPa depending on the number of freeze-thaw cycles (one to eight).The phantoms of tubular body with different elasticity were fixed in the fluid system. The information of flow field in the vascular phantom was obtained using the newly developed ultrasound velocimetry technique (echo particle image velocimetry). The flow rate and the pressure at the upstream of the vascular phantom are respectively measured by the Flow Meter and the Pressure Transmitter.
Blood clot characterization by ultrasound Nakagami imaging
Authors: Tsui Po-Hsiang , Hung Chieh-Ming , Hsu Chung-Hsin
Published: April 2012

Detection of blood clotting by ultrasound has been widely explored. Many ultrasonic quantitative parameters have been demonstrated to have the ability to characterize clot. This study proposes the ultrasound Nakagami image as a tool to visually characterize the properties of blood clot. Whole blood samples with a hematocrit of 40% were made. A 10-mL whole blood was placed in a tube and 1 mL of 0.2 mol/L CaCl2 solution was added to induce clotting. A 35-MHz focused transducer was used to scan the tube filled with blood before and after blood clot formation for Nakagami imaging. The results showed that whole blood and clot have similar textures in their B-scans, but the Nakagami image behaved well in distinguishing between blood and clot. The Nakagami image before clot formation is based on red-blue-interlaced shading, corresponding to Rayleigh distribution (the Nakagami parameter m approaches 1). However, the clot has more blue shadings in the Nakagami image, representing that the backscattered statistics of blood clot tends to be pre-Rayleigh distributed (m < 1). This study suggests that the Nakagami image may be used to characterize blood and clot for clinical studies and diagnosis.
Experimental investigation of a bone-conducted ultrasonic hearing system based on a DSP platform
Authors: Yu Ziying , Shen Junxian , Yang Jun
Published: April 2012

Ultrasonic signals can be conducted and perceived by bones when a certain part of human skull is pressed. Experiments show that hearing-impaired people may be able to perceive ultrasound, distinguish different frequencies, or even recognize words after training. This finding is very promising for hearing-aid studies. In this paper, a novel bone-conducted ultrasonic (BCU) hearing system is developed. Both the software simulations and experiments on human subjects are carried out. The BCU hearing system is implemented on a DSP platform to achieve an appropriate modulation strategy. An ultrasonic vibrator is attached to the system, allowing the audible sound signals to be demodulated from the ultrasonic region via bone conduction. Different carrier frequencies and modulation algorithms are examined and validated in this platform. To evaluate system performance, perception tests are also conducted on the deaf and normal-hearing subjects. Experimental results show that the proposed system can operate as a flexible experimental platform suitable for BCU hearing studies.
Acoustic wave propagation in cracked porous rocks and application to interpreting acoustic log data in tight formations
Authors: Tang Xiaoming , Chen Xuelian
Published: April 2012

Rocks in earth's crust usually contain both pores and cracks. Typical examples include tight sandstone and shale rocks that have low porosity but contain abundant microcracks. By extending the classic Biot's poroelastic wave theory to include the effects of cracks, we obtain a unified elastic wave theory for porous rocks containing cracks, adding crack density and aspect ratio as two important parameters to the original theory. The new theory is applied to interpret acoustic velocity log data from tight sand and shale gas formation, whereas the classic Biot theory has difficulty in explaining such data. Because the flat- or narrow-shaped cracks can easily deform under acoustic wave excitation, the acoustic property of a cracked porous rock is quite different for different saturation conditions. This allows the new theory to correctly predict the trend of velocity variation with gas saturation in low-porosity rocks, providing a useful interpretation tool for acoustic logging in tight formations.
Numerical study on the acoustic field in noncircular elastic pipes filled with fluid
Authors: Zhang Hailan , Che Chengxuan , He Xiao , Wang Xiuming
Published: April 2012

Due to the high cost of real field test, the testing and calibration of acoustical logging tools are usually conducted in a steel pipe filled with fluid. The information provided by the calibration in a circular pipe is not proper for nonaxisymmetric dipole tools. So the possibility of using a noncircular pipe filled with fluid for the testing and calibration of acoustic dipole logging tools is considered. In our previous report the acoustic fields generated by a dipole source in the noncircular fluid waveguide with the rigid wall were numerically studied using the finite-element software package of Comsol Multiphysics. So called 2.5D method has been used. The transformed acoustic field in a frequency wave-number domain is calculated first and from which the acoustic field in the time space domain was obtained by a 2D Fourier transformation. In this report the method is extended to include an elastic wall instead of the rigid boundary of the fluid waveguide. The results show that the contribution of the elastic wall is significant to the whole acoustic field and the propagating modes in the waveguide are coupling of the modes in the fluid part with that in the elastic wall.
Elastic metamaterials with negative bands
Authors: Wu Ying , Lai Yun , Sheng Ping , Zhang Zhaoqing
Published: April 2012

The unusual properties of a metamaterial come from special resonances supported by its resonating structure units. Guided by a previously developed effective medium theory, which links the resonances of the microstructures and the unusual properties, two types of elastic metamaterials in two dimensions were designed with different resonant structures in their building blocks that exhibit multiple negative dispersion bands with special characteristics. The first type possesses negative mass density and negative shear modulus simultaneously over a large frequency regime, which leads to a negative band for shear waves only. Mode conversion takes place at the interface of the metamaterial and the common solids. The second type is able to produce negative effective moduli in different frequency regimes within a large frequency regime of negative effective mass density. This results in a super anisotropic negative band and a negative band that only compressional is allowed. All of these unusual properties are demonstrated by simulations. This work was supported by Hong Kong RGC Grant No. 605008, HKUST604207 and KAUST start-up package.
Vibroacoustic characteristic of membrane-type acoustic metamaterials
Authors: Zhang Yuguang , Wen Jihong
Published: April 2012

Acoustic barriers with effective sound insulation performance can find many useful applications in the area of aerospace, automotive vehicles and environmental noise control. However, traditional acoustic barriers are always not effective at low frequencies due to the mass law. Membrane-type acoustic metamaterials have been shown to exhibit unique sound insulating performance at low frequencies (100-1000Hz). The structure of membrane-type acoustic metamaterials can be simplified as a stretched, rim fixed membrane carrying a distributed mass. There are publications on beams, rods and plate with uniformly distributed mass, but the vibration equation of membrane is different from the plate, and the presence of air around the membrane needs to be properly included. In this paper, we present an analytical model of this type acoustic metamaterials. The transmission loss and vibration characteristic are then described using the coupled structural-acoustic model. The validity of the model is confirmed by comparing our analytical results with the FEA calculations and experimental measurements in existing publications.
Application of microperf and microslit absorbers
Authors: D'Antonio Peter
Published: April 2012

The theory of microperf and microslit absorbers is well established. Theoretical predictions match measurements with a high degree of accuracy. A normal incidence impedance tube measurement of a microperforated metal panel will illustrate this agreement. In this presentation, I would like to discuss how these transparent and translucent foils and panels have been used as both acoustical and decorative elements in projects. The microperf design is available in polycarbonate and ETFE foils as well as panels. The foils can also be printed for light shading. Since polycarbonate transmits in the infrared, the translucent foils can be used with back lighting on radiant ceilings. Several projects will be presented. The microslit design is typically available in panels, which can be transparent, translucent and digitally printed in graphic designs and signage. A graphically printed microslit atrium project will be profiled illustrating the architectural acoustic potential of this approach. These relatively new absorbers add an important tool to the acoustical palette and this presentation will illustrate how they have been used in a wide range of projects.
Non-flammable woven acoustic flow resistive textile
Authors: Kierzkowski Marek
Published: April 2012

Flow resistive textiles are becoming more popular almost in all aspect of acoustic applications where sound absorption is a primary noise reduction countermeasure: industrial acoustics (reduced sound propagation in work places), architectural acoustics (shaping interior acoustic properties) and the automotive acoustics (bonnet liners, firewall insulators). While the automotive applications are not very demanding in terms of flammability, the industrial and architectural applications must comply with severe flammability restrictions. As it is today only non-flammable porous materials like mineral fibre, ceramic fibre or melamine foam would comply with stringent fire specifications. We will show that the wise choice of the flow resistive textile enable to widen the range of materials complying with actual standards. The traditionally good sound absorbers like polyester fibre or foam could then become available to architects again.
An approach for moving target detection with airborne CTFM sonar
Authors: Wang Yang , Xu Yong , Cao Benxi , Wang Jingyao , Yang Jun
Published: April 2012

Continuously Transmitted Frequency Modulated (CTFM) sonar transmits wideband acoustic signal, demodulates the echo signal, and calculates the target distance by acquiring the frequency of the demodulation output signal. Still objects can be accurately detected using CTFM sonar. However, moving target brings Doppler shift to the echo signal frequency, which makes the output signal frequency of CTFM sonar deviate from the accurate distance of the target. In this paper, a novel airborne sonar sensing approach is proposed. Using a modified transmitted signal, single moving target that appears in a static environment can be detected. Compared to traditional CTFM sonar, a single tone is added to the transmitted signal. The existence and radial velocity of a moving target can be calculated based on the single tone Doppler shift of the echo. Furthermore, the simultaneous kinematic information of the target can be extracted by the system algorithm. An experimental system is developed, and the result of experiments verified the feasibility of the approach.
Echolocation beam shape and focusing in the false killer whale (Pseudorca crassidens)
Authors: Kloepper Laura , Nachtigall Paul , Breese Marlee
Published: April 2012

Odontocete echolocation signals are thought to be focused by the melon and air sacs, although active focusing has yet to be demonstrated empirically. Because odontocete echolocation signals are variable and the emitted click frequency greatly affects the echolocation beam shape, investigations of beam focusing must account for frequency-related beam changes. Using a fine scale hydrophone array, we measured the shape of the echolocation beam and tested whether the echolocation beam of a false killer whale changed depending on target difficulty and distance while also accounting for frequency-related changes in the echolocation beam. The false killer whale produced a single-lobed echolocation beam that changed in size depending on target distance and difficulty which may be a strategy of actively controlling the emitted beam to maximize energy of the target echo.
Correlations between propagation characteristics of guided ultrasonic waves and long bone fatigue
Authors: Ta Dean , Zhang Zhenggang , Wang Weiqi
Published: April 2012

Ultrasonic assessment of long bone has become a topic of interest in recent years. The objective of this paper is to analyze the propagation characteristics of guided ultrasonic waves in fatigue long bones, further to study the influence of varying elastic modulus (EM) of long bones on these characteristics. A hollow cylinder was used to mimic long bones and then to calculate the velocities and wave structures with various EMs. Besides, finite difference time-domain (FDTD) method was used to simulate the propagation of guided waves in long bones at different EMs. The results show that phase/group velocities and central frequencies of guided waves decrease with the decrease in EMs. However, the attenuation of wave modes decrease with increasing EMs. The simulated results of FDTD for all wave modes and parameters are in good agreement with theoretical values. Those results demonstrated that different modes have diverse sensitivity to the variation of EMs, and mode velocities, central frequencies and attenuations can reflect the change of EMs of long bone. Therefore, the propagation characteristics of guided ultrasonic waves may provide a feasible approach to evaluate the early stages of fatigue damage in long bones.
Modelling and computation of boundary layer flow around body of revolution
Authors: Hua Xie , Hong-cui Shen , Yu-kui Tian
Published: April 2012

The characteristic parameters of boundary layer are inputs for the flow noise calculation, their change influence the power spectra of wall pressure fluctuations, so as to affect the analysis of the flow radiation noise. In this paper Hess-Smith boundary element method was adopted to model thick boundary layer for body of revolution. The corresponding code is developed. The computation of characteristic parameters of boundary layer for a body of revolution is carried out. The computed results including boundary layer thickness, shape factor, momentum thickness and friction coefficient are analyzed. The variation of characteristic parameter is obtained. The result showed that the code developed in this paper can be applied to the analysis of the body of revolution's 3D boundary layer calculation, which can offer input parameter for flow noise calculation. Key words: flow noise, characteristic parameter, boundary layer, body of revolution, Hess-Smith boundary element
A numerical study of the effects of a winglet on airfoils
Authors: Wang Chao-Nan , Tse Chuan-Cheung , Chang Ya-Ju
Published: April 2012

The purpose of this research is to investigate the effects of a winglet on aerodynamic noise of an airfoil. For simplicity, Reynolds Averaged Navier-Stokes equations combined with Realizable turbulence model are used to solve the turbulent flow. In order to verify the accuracy of flow field analysis, a uniform flow past a three-dimensional rectangular airfoil is analyzed and tracks the center line of the tip vortex. The agreement between the simulated and measured center line is good. For the sound field analysis, the flow induced noise around a rectangular airfoil is computed by the Broadband Noise Source (BNS) model. Proudman's formula was used to evaluate acoustic power per unit volume of aerodynamic noise. This study focuses on the sound power of aerodynamic noise generated by tip vortex when the flow passes through an airfoil and an airfoil with winglet. In order to understand the effects of the winglet on the aerodynamic noise, the different winglet characteristics are investigated and discussed. It is found that with a winglet the dynamic coefficient is improved and the generated sound power is also reduced by about 5.4 dB in this study.
Simulation of compressible flows using Hermite methods
Authors: Hagstrom Thomas , Appelo Daniel , Colonius Tim , Inkman Matthew , Jang Chang Youn
Published: April 2012

Spectral element methods based on Hermite interpolation have a number of unique properties. First of all, the stabilization inherent in the interpolation process is sufficient to suppress nonlinear instabilities observed with other discretization schemes and leads to accurate linear transport of nonsmooth solutions. Second, and most important, they allow purely local time-stepping procedures limited only by geometric domain-of-dependence requirements. Thus high-order Hermite methods maximize the computation-to-communication ratio and therefore they admit highly efficient implementations on multicore processors. In this talk we focus on the application of Hermite methods to simulate unsteady compressible flows. Examples will include the direct simulation of the aeroacoustics of a low Reynolds number subsonic jet, as well as studies of more basic sound radiating flows. The latter will illustrate the coupling of Hermite methods with more standard discontinuous Galerkin discretizations to handle physical boundaries.
Control of weak perturbations
Authors: Williams J. E. Ffowcs , Huang L.
Published: April 2012

We define sound as being a weak perturbation in the properties of material consistent with the Navier-Stokes and continuity equations. Lighthill's pioneering paper on aerodynamic noise gives an exact theory that enables interesting connections to be made between flow and sound. Aerodynamic noise being caused by quadrupoles is a good point of view, but what caused the quadrupoles? Were they possibly initiated by sound? Conclusions deduced from such a theory are not necessarily helpful, but they are true and might be very helpful indeed. The linear perturbations we call sound obey linear rules and it can be suppressed by anti-sound, a subject now becoming both practical and useful. The same must apply to any weak perturbation of a dynamic system perturbed from rest. Some perturbations are unstable and grow exponentially in their early weak state. They might be eliminated altogether by suppressing their linear form. The Rijke tube experiment shows that to be practical and shows also the close similarity that exists between acoustics and control theory. The lecture will give more examples of that type and suggest others that have yet to be demonstrated.
One person view on publishing in JASA and JASA Express Letters
Authors: Au Whitlow W. L.
Published: April 2012

One of the strengths of the Acoustical Society of America (ASA) is the multi-disciplinary aspects of the society. Engineers, physicists, mathematicians, biologists, psychologists, physiologists, and speech researchers plus others are part of our society. The ASA can be broadly divided into two groups, those in the physical sciences and those in the life or natural sciences with signal processing bridging both groups. JASA reflects this diversity. Manuscripts by those in the physical sciences depend heavily on mathematical and physical modeling and various types of equations, while in the natural sciences spectrograms, various types of statistics and hypotheses testing are often used. Nevertheless, certain factors with regard to quality must be met by all authors. The articles should contribute new knowledge, be written in English and be grammatically correct. The approach or methodology must be sound. The results should be clearly presented whether in tables, graphs or in verbiage. Finally, the discussion and conclusions should be to the point, clearly presented so the authors' arguments and points can be easily understandable. Associate editors should be assisting authors in getting their papers published. Responsibility for the content lies totally with the authors and not one bit with the associate editors.
Authors' sharing on handling reviewers' comments
Authors: Tang S.K. , Cheng L.
Published: April 2012

JASA is a highly reputable journal in acoustic community and publishing in the journal is very important to academia. In the universities in Hong Kong at least, a publication in JASA could affect staff appraisal outcome. The journal has very professional editors and a secretariat office, who screen all the submissions before sending them out to reviewers. To publish in JASA, quality of the work is certainly of prime importance. However, the responses to reviewers' comments can sometimes play an important role in the process, especially on controversial issues. We believe that authors and reviewers are equal in the whole process but comments from both the editors and reviewers must be handled professionally. In this presentation, we would like to offer our views from an author's perspective. In particular, we would like to share some experiences and discuss some issues which we think could affect the final decision on a submission.
Toward an effective use of timbre in data sonification
Authors: Terasawa Hiroko
Published: April 2012

The spectro-temporal structure of a sound determines its timbre, and carries musically interesting information such as instrument type and performance expressions. Using timbre in data sonification can be viewed as an inverse transform of this process: Expressing data with timbre is equivalent to designing the spectro-temporal structure of a sound. Taking that into account, timbre is most effectively used in sonification by projecting time-series data onto the spectro-temporal structure of a sound. The temporal structure of the data often differs from the archetypal spectro-temporal structure of traditional instrumental sounds. But this discrepancy contributes to novel musical expression, based on novel timbre design. From this perspective, some sonification works are presented, such as ones produced by sonification of dynamic motion of genetically-modified worms and dynamic transitions of brain-wave data. Based on these examples, methods for effective and expressive use of timbre in data sonification will be presented.
Research on decentralized adaptive active control for a single-layer vibration isolation system
Authors: An Fengyan , Sun Hongling , Li Xiaodong , Tian Jing
Published: April 2012

In this paper, an investigation on decentralized adaptive active control for a single-layer vibration isolation system is introduced. The vibration isolation system consists of a honeycomb table as a vibration source, four rubber isolators in parallel with electromagnetic actuators, and another honeycomb table connected with a rigid base by four rubber isolators as a flexible base. Both simulations and experiments show that the decentralized controller exhibits good performances at frequencies where the tables could be dealt with as rigid bodies. At higher frequencies, however, the system could not work stably because flexible vibrations of the tables become dominant. An experimentally validated optimization method for internal parameters of the decentralized control algorithm is proposed to improve the stability and convergence of the control system.
Perceived soundscapes in relation to transport related annoyance, context and personal characteristics; psychometric analyses
Authors: van Kamp Irene , van Kempen Elise , Houthuijs Danny
Published: April 2012

Most studies into perceived soundscapes have addressed subjective soundqualities at a (very) low scale level, such as parks, recreational area's and squares. Studies into the effects of transport related noise seldom incorporate perceived soundscapes and are typically focussed on negative effects, such as annoyance, sleepdisturbance and environmental worry. It would be valuable to know how people describe their sound environment in areas with varying levels of road-, air or rail noise. Available data on perceived soundscapes from the two Schiphol surveys in 2002 and 2005 allowed us to perform such analyses. The intercorrelations were studied between dimensions of perceived soundscapes, annoyance, arousal as well as several measures at the contextual, social and psychological level, sometimes referred to as non-acouticsl factors. Results shed light on the construct validity of the perceived soundscape scale and may contribute to further refinement of this instrument.
The link between soundscape perception and attention processes
Authors: André Fiebig
Published: April 2012

In order to understand the perception and evaluation of soundscapes, it appears mandatory to concentrate not only on constellations of sources and their contributions to the acoustic environment, but also to consider attention processes towards sound sources. It is widely known that a listener can easily focus on a certain source and can suppress the noise of other sources, which is called cocktail-party effect. It is assumed that this effect greatly influences the general appreciation of the whole soundscape. However, the process, why people focus on certain sound sources and how this influences the overall evaluation, has to be explored. A detailed knowledge about the (often subconscious) focussing on sources in multi-source soundscapes would be very helpful for design purposes, to attract deliberately attention to certain sound sources leading to positive feelings for the majority of soundscape visitors. Laboratory results dealing with the effect of source attention and its impact on soundscape evaluation were already published. In these surveys it was found that the processes, in which way the global impression changes due to the attention attraction to certain sources, seem to be complex. The paper will focus now on in-situ assessments and will show new results gained in field experiments.
Measurement of the sound pressure in the focal spot area of line-focus ultrasound field by Schlieren technique
Authors: Jiang Xue-Ping , Cheng Qian , Qian Meng-Lu
Published: April 2012

Schlieren method is an effective method for studying the sound field in transparent medium which called phase objects. The method is used to research the acoustic field by analyzing the refractive index changes induced by the acoustic wave. Calculations of the sound pressure distribution radiated by the line-focus ultrasonic transducer are implemented, and the acoustic field in the focal spot area is obtained. Then the diffraction light intensity on the Fourier transform plane in a Schlieren system is calculated with two-dimensional Fourier transformation when the phase object is the ultrasonic wave. Because the light intensity of the different diffraction spots on the back focal plane of the transform lens depends on the sound pressure, the sound pressure in the focal spot area can be determined using Schlieren technique. A Schlieren system is set up. The images of the line-focus ultrasonic field are obtained and the sound pressure in its focal point area is measured non-invasively by measuring and comparing the light intensities of the different diffraction spots. This work is supported by the National Natural Science Foundation of China (No. 10804085)
Micro-organization and plasticity of the primary auditory cortex
Authors: Kanold Patrick
Published: April 2012

The auditory cortex is a laminated structure that adaptively processes sensory information from the external environment. The precise nature of the transformation of sensory information at the level of cortical networks is unknown. We use in vivo two-photon calcium imaging techniques to measure response properties and functional organization of primary auditory cortex (A1) neurons in mouse. We find that frequency selectivity in supragranular layers is heterogeneous on small spatial scales and that this heterogeneity is likely created from sampling of diverse inputs to supragranular neurons. The large frequency range of inputs available to each neuron might provide a substrate for a large degree of plasticity in individual neurons. We tested the capacity of A1 neurons to rapidly change tuning properties by using micro-stimulation of top-down projections to A1 and pairing such stimulation with a particular sound. We find that the frequency tuning of individual neurons can rapidly be changed leading to an increase in the representation of the paired sound. Collectively, these results provide insight into how sensory information is represented and adaptively transformed in auditory cortex.
Auditory cortical plasticity—from synapse to perception
Authors: Schreiner Christoph , Froemke Robert
Published: April 2012

Synapses and neuronal receptive fields of the cerebral cortex are plastic. Enhancements and decreases to auditory cortical excitatory synapses can be induced by pairing acoustic stimuli with activation of the nucleus basalis neuromodulatory system. Similarly, the feature selectivity of individual neurons and cell assemblies can be modified in a manner that depends on the patterns of network activity, the engagement of neuromodulatory systems, as well as by sensory experience. Perceptual performance has been shown to change as a consequence of experience and learning. The relationship between synaptic and receptive field changes and perceptual plasticity, however, is poorly understood. We used in vivo whole–cell recordings and behavioral testing to explore that relationship in more detail. We will discuss how synaptic modifications and receptive field changes are reflected in the encoding of frequency and intensity information in rat auditory cortex and demonstrate that these changes are expressed in the perceptual behavior of animals in sensory detection and classification tasks. It is concluded that direct modification of specific cortical inputs leads to wide-scale synaptic changes, which collectively support improved sensory perception and enhanced behavioral performance. Supported by NIH Grants DC02260 (to CES) and DC009635 (to RCF)