bluuebunny/crossref_metadata_2025 huggingface dataset:
In-situ characterization of hedges with a parametric acoustic transducer
Authors: Horoshenkov Kirill , Khan Amir , Yang Hongseok , Cheal Chris , Smyrnowa Julija , Kang Jian
Published: April 2012

This work reports on the results of outdoor measurements which were carried out using a highly directional parametric acoustic transducer and a 2-D array of microphones. The purpose of these measurements was to determine the frequency and angular dependence of the acoustic transmission loss of hedges (hedgerows). The experimental setup and procedure used in this work enabled us to simulate an approximately plane wave propagation regime and to reduce considerably the effect of ground on the recorded transmission loss data. The results show that a 1.5-2.5m thick hedge can provide a considerable (up to 20 dB) transmission loss which is comparable to that expected from an artificial noise barrier structure. The theory developed by Aylor (JASA 51(1), 197-205, 1972) is used to explain the observed dependencies as a function of the leaf density, size and hedge thickness. An alternative equivalent fluid theory for porous absorber (Horoshenkov et al, JASA 104(3), 1198-1209, 1998) is also used to explain the observed attenuation for sound propagation through the leaf mass.
Characterizing the properties of adhesive in bonded materials by laser ultrasonic method
Authors: Xu Xiaodong , Liu Cong , Liu Xiaojun
Published: April 2012

In order to characterize the quality of adhesive in bonded materials, a metal/bonding/metal assembly model named as “sandwich” model is used to characterize the propagating properties of Lamb wave generated by laser ultrasonic method and studied in theory and experiment. In our experiment, a Nd:YAG ns laser is focused as line source and scanned on the surface of sample to supply signals in time and space, the signals of traveling lamb wave is detected by a beam deflection system. The dispersion curve of Lamb wave is deduced based on 2D FFT of obtained signals. According to the theoretical “sandwich” model, the real part and imaginary part, which is corresponded to the attenuation coefficients of sample, of elastic parameters of sample in wideband frequencies can be determined by theoretical fitting to the dispersion curve, and the determined parameters are reflected the changing properties of the adhesive in bonded materials.
Investigation of simultaneous signal transmission in non-destructive inspection of steel billet
Authors: Norose Yoko , Mizutani Koichi , Wakatsuki Naoto
Published: April 2012

A non-destructive method of steel billet, which uses time-of-flight of ultrasonic longitudinal wave and detects defects as decrement of pseudo sound velocity reconstructed by computerized tomography, has proposed. The remaining problem is long measurement time, owing to step-by-step measurement corresponds to each sound path whose number becomes huge. One of the solutions is simultaneous measurement, which can be achieved by transmitted signals simultaneously. To avoid interference among signals, choice of the transmitted signal becomes one of the most important points to be considered. In the case of non-destructive inspection of steel billet, many reflected waves from boundaries may cause adverse influence. Therefore, in this study, the parameters of the signal; modulation scheme, modulated signal, signal length, and signal frequency are investigated. Simulation-based study suggested that the signal is required to be short and independent each other. From those conditions, some experiments about defect detection by the several kinds of modulation schemes using pseudo-random noise were conducted. As a result, defects detection by 5ch simultaneous transmission was successful. It was suggested that the total measurement time could be decreased to 1/5.
A passive dispersive wave amplifier for high-intensity broadband acoustic pulses
Authors: Dion Steven , Brouillette Martin , Riel Louis-Philippe
Published: April 2012

The acoustical power output of piezoelectric ultrasonic transducer is limited by the material breakdown voltage or the available driving electrical power. While there are well known ways to passively amplify monofrequency acoustic waves generated by a single transducer, e.g., with an exponential horn, there is no obvious way to similarly pump energy into a structure to produce high-intensity broadband acoustic pulses. It was found that the frequency dependant phase velocity inherent to dispersive waveguides can be advantageously exploited to generate high intensity planar pulse waves using a single transducer. With this amplification concept, gain factors as high as 15 have been measured, which can be exploited to produce shock waves in water with a conventional ultrasonic transducer and low power electronics. The paper will present the theoretical underpinnings of this method, as well as its experimental validation. Some potential biomedical applications of this technology will also be discussed.
A circular microphone array design approach for discrete noise suppression
Authors: Yang Bo , Feng Jie , Wen Ming
Published: April 2012

A broadband detection performance of a circular microphone array has been degenerated by discrete noise interference. In this paper, a circular microphone array optimum design approach is proposed for discrete noise suppression in acoustic detection in the air. This approach utilizes the noise information of acoustic propagation's transfer function to mitigate its effect on broadband microphone array detection processing. It is demonstrated to be feasible to improve passive broadband detection ability of the circular microphone array through the adjustment of array shading weights. This is accomplished by numerically maximizing the deflection coefficient under the assumption of a small signal-to-noise ratio. Under this approach, the conventional beamformer is not redesigned, and only the shading weights of the conventional beamformer are adjusted.
A new acoustic target recognition method based on gaussian mixture model
Authors: Wen Ming , Feng Jie , Yang Bo
Published: April 2012

Target recognition is one of the most important components of an acoustic detection system. Conventional acoustic target recognition algorithms base the classification results on features from a single frame of signal, suffering from inability to take the dynamic characteristics of acoustic signal into account, which can significantly increase the separability of acoustic targets. In this paper, we present a novel method for acoustic target recognition. Acoustic signal to be classified is divided into a sequence of signal segments. Gaussian mixture model is employed to model the sequence, and EM algorithm is utilized to learn the parameters. This idea is motivated by the interpretation that the Gaussian components can represent some general target-dependent spectral shapes. Experimental results show that the method achieves high recognition accuracy on different data sets, and is highly robust to ambient noise.
The enhancement of pulverized-coal combustion by using sound waves
Authors: Jiang Genshan , Zheng Yingchao , Pan Jie , Tian Jing
Published: April 2012

A model for the enhancement of pulverized coal combustion in high-intensity acoustic fields has been developed. In a power boiler pulverized coal particles and char are entrained in the main gas flow for a significant length of time. The slip velocity between the entrained particles and the gas is very low leading to low heat and mass transfer to and from the particles. This results in long combustion times for the particles, particularly if the combustion is diffusionally controlled. When a high-intensity acoustic field is applied to the gas flow, it superimposes high-velocity oscillations on the main flow. If the frequency and amplitude of this acoustic field is just right, the particles are not entrained in the acoustically induced flow oscillations. This creates a periodically varying slip velocity between the particles and the hot gas, leading to higher convective heat and mass transfer to and from the particles, thereby enhancing the combustion. The paper also presents the axial pressure gradient and shear stress in neighborhood of the particles placed in sound field.
Trailing edge noise mitigation investigation for wind turbine blades
Authors: Asheim Michael J. , Munoz Dave , Moriarty Patrick
Published: April 2012

Wind turbines offer one of the most mature technologies for providing large scale renewable energy to society in an economically viable way. Although not on par with the price of conventional energy sources yet, the cost of energy has been steadily decreasing as the technology continues to develop. Unfortunately, like with all energy sources, there are some problems with this form of generation. Among these, sound emissions from wind turbines are one of the problems people who live close to the installed machines may be exposed to. Past studies show that these noise emissions are dominated by aeroacoustic noise and of the many mechanisms that lead to aeroacoustic noise, the interaction between the unsteady flow and the trailing edge seems to constitute the largest portion of the overall sound spectrum. Modifications to the trailing edge geometry will change how the fluid interacts with the trailing edge and can be used to change the resulting noise emission. This study will investigate the effect passive trailing edge devices have on the overall noise emission from a wind turbine, in an attempt to reduce the aeroacoustic noise being generated by the turbine.
Data collection for individuality analysis on subjective music similarity evaluation
Authors: Kawabuchi Shota , Miyajima Chiyomi , Kitaoka Norihide , Takeda Kazuya
Published: April 2012

Recently there are many studies of subjective music similarity for music information retrieval. To quantify the subjective music similarity, there are many factors to take into account. In this study the individuality of the subjective similarity was focused on. To analyze the individuality of the subjective similarity, subjective evaluation data for 200 pairs of RWC popular music database was collected. 28 subjects listened to the pairs of tracks, and evaluated similarity of each pair by similar or dissimilar. They also selected the components of music (melody, tempo/rhythm, vocal, instruments) that was similar. Each subject evaluated the same 200 pairs, thus the individuality of the evaluation can be easily analyzed. The results of pilot analysis were reported.
Minimum models for self-sustained oscillations of conical reed instruments
Authors: Kergomard Jean , Guillemain Philippe , Silva Fabrice
Published: April 2012

It is now well known that a minimum model for self-sustained oscillations of clarinet-like instruments is the iterated map model, leading to square signals. The reed is assumed to be without dynamics, while losses are ignored (or assumed to be independent of frequency). The generalization to conical instruments is not straightforward. For the present work, the minimum model is used for a truncated cone instrument, but the missing part of the cone is not assumed to be small compared to the wavelength. Thus the result should be a signal without sharp corners. However, without any kind of mouthpiece, no periodic sound can be obtained in a steady-state regime. It will be explained that the choice of a model for the mouthpiece can be done without adding any supplementary parameter (therefore a conical resonator has one parameter only more than a cylindrical one). It is shown that several choices are possible, allowing either the use of: the same inverse nonlinear characteristic than for clarinet-like instruments, or any direct nonlinear characteristic, leading to a great simplicity. Advantages and drawbacks of several solutions are discussed.
Active noise control in the exhaust port of a vacuum cleaner
Authors: Wang Ping , Tao Jiancheng , Qiu Xiaojun
Published: April 2012

Exhaust port is one of the main sound transmission paths for noise radiation of a vacuum cleaner. Porous sound absorption materials are usually stuck at the inner surface of the exhaust port to absorb the noise; however the noise reduction performance, especially at low frequency, usually is limited due to the limited transmission path length to the exhaust port for airflow and the low acoustical absorption coefficients of porous materials at low frequency. In order to reduce the low-frequency noise which radiates outside through the exhaust port, active noise control technologies are applied in exhaust port, where the configurations of the active control units including the reference sensor, the control loudspeaker and the error microphone are investigated. Finally, experiments are carried out for performance validation.
Variable step-size μ-law memorised improved proportionate affine projection algorithm for sparse system identification
Authors: Xiao Longshuai , Yang Jun
Published: April 2012

System identification has wide applications in adaptive echo/feedback cancellation, active noise control, adaptive channel equalization, etc. When the system is sparse, recently, a μ-law memorised improved proportionate affine projection algorithm (MMIPAPA) has been proposed to improve the misalignment performance remarkably. However, the MMIPAPA with constant step-size has the conflicting requirement of fast convergence rate and low steady-state error. To solve this problem, a variable step-size version of the MMIPAPA (VSS-MMIPAPA) has been extended by setting each component of the a posterior error energy vector equal the system noise energy. Furthermore, through an alternative method to compute the variable step-size, when the estimated component of the a prior error energy vector is smaller than the system noise energy, further lower steady-state misalignment is achieved. This method leads to an improved VSS-MMIPAPA (IVSS-MMIPAPA). The computational complexity of the IVSS-MMIPAPA is O(P2L), which may be too high for many applications. Therefore, an approximate algorithm with little performance degradation has been implemented using recursive filtering and dichotomous coordinate descent iteration techniques, by which the complexity has been reduced to O(PL). Finally, the efficiency of both the exact and approximate algorithms developed here has been verified by simulation results.
Building active noise control system decrease MRI driving sound
Authors: Nakayama Shohei
Published: April 2012

Our purpose is to build Active Noise Control (ANC) system for MRI examination. It is problem for the patients that loud sound which is generates by Magnetic Resonance Imaging (MRI) equipment. Its maximum of the sound pressure level is over 100dB. It does not only make patients sickening, but has possibility of hearing loss. Patients' hearing ability is protected from the loud sound by the ear protectors. The ear protectors decrease around 20dB from the sound. Its performance is unsatisfactory to decrease the MRI driving sound for the patients. Because the patients hear the high level sound which the maximum sound pressure level is over 80dB if any wearing ear protectors. They hope for more the performance. We have an idea that we build the ear protectors whose ANC system controlling low frequency. It is important for the feed-forward ANC system to decide the reference point. We show that the result measured the MRI driving sound for finding the sound source. As a result, we found the sound source is located around the gradient coil. We show computer simulation result that ANC system whose reference point located on the sound source controls the MRI driving sound.
A soundwalk study on the relationship between soundscape and overall quality of urban outdoor places
Authors: Nilsson Mats E. , Jeon Jin Young , Rådsten-Ekman Maria , Axelsson Östen , Hong Joo Young , Jang Hyung Suk
Published: April 2012

In a field study, we explored the relationship between the soundscape and the overall quality (good - bad) of outdoor open places. Thirty three residents in down town Stockholm participated in soundwalks near their homes. Along the soundwalk route, the participants assessed six places with respect to the soundscape, the visual environment and the overall quality of the place using a questionnaire. The six locations were preselected to vary in acoustic and visual quality. A regression model with pleasantness of the auditory and visual environment as predictors explained a substantial part of the variance in assessments of the six place's overall quality. To disentangle the specific effects of auditory and visual aspects, the present study will be complemented with laboratory experiments in which visual and auditory aspects are independently manipulated.
Thinking soundscapes into the management of country parks
Authors: Marafa Lawal , Lam Kin Che , Brown Lex
Published: April 2012

Countryside and Country Parks, commonly used as an area for recreation, conservation and education, accommodates sunlight and allows free air movement, thus providing visual relaxation. In recent years, ways to make country parks more attractive for use have been highlighted worldwide. Among a number of promoted common themes regarding the protection and enhancement of country parks, sound as a component of the biological and social environment should be utilized for improving the general environmental quality. Based on the large scale field recordings and questionnaire surveys carried out in 3 country parks in Hong Kong countryside, the relationship between subjective evaluation of soundscape and landscape quality as well as the particular contribution of sound in the enhancement of country parks have been statistically analyzed. Results of this study demonstrate a close relationship between subjective evaluation of landscape quality and acoustic quality. Identification of different sound sources in different functional zones, their particular properties and influence on subjective evaluation of the acoustic quality suggests an alternative approach for improving the acoustic quality and consequently the general environmental quality at the countryside location. Keywords: Country Park, Country side, Recreation, Soundscape
Constructing the ideal soundscape: a practical study on closing the gaps between soundscape and urban designers
Authors: Steele Daniel , Luka Nik
Published: April 2012

Calls are increasingly made for an urban land-use policy that takes non-vision sensory modalities into account, like hearing, but agents capable of making such changes often lack the expertise to do so. The best progress in acoustics so far has been through intentional soundscape design, which considers sound during the urban design process rather than after. Indeed, soundscape designers should understand how complicated factors play out in-situ, such as findings linking increased driving speeds with acoustically treated roads. Armed with this knowledge, they can take action to prevent further harm to the urban landscape. In practice, however, what can happens is 1) papers in soundscape are written in language not interesting to urban designers; 2) research studies examine the current environment without proposing design updates; and 3) different investigators fail to agree on what constitutes wanted and unwanted noise. Each of these shortcomings contributes to a built environment that reflects little of our sophisticated understanding. In response, this presentation will: demonstrate how soundscape research can fit into current urban design frameworks; review the literature to suggest some small and large acoustically-optimized urban designs; and encourage collaboration channels for the direct flow of soundscape research into urban design practice.
Changes of soundscape along rural-urban gradients and their influence on landscape preference: a case study from Xiamen, China
Authors: Gan Yonghong , Luo Tao , Behm Holger , Coppack Timothy , Liu Jiang
Published: April 2012

Humans percept their environment mainly visually, but the acoustic background may have a strong effect on overall landscape preference. Through urbanization, not only the appearance, but also the acoustic background of a landscape is changed. In this paper, the following questions are addressed: (a) How does urbanization change soundscape, in terms of its composition and intension? (b) To what extent does soundscape perception affect the process of landscape preference? With audio and video data from field investigations carried out in Xiamen, China, the differences in composition and intensity of soundscapes along the rural-urban gradient were identified. In surveys with sixty test persons, human perception of visual landscape and soundscape, as well as the preference of overall landscape, were measured. Visual, acoustic, and overall landscape quality of the study area was mapped on the basis of a land-use map. The influence of visual and acoustic factors on overall landscape preference is discussed in view of potential methodological approaches for mapping overall landscape quality by integrating visual with acoustic qualities of landscape. This may provide the basis for an objective multivariate assessment tool in landscape planning. Acknowledgment:Project supported by National Natural Science Foundation of China(40971111) and Natural Science Foundation of Fujian Province, China (2011J01280).
A full-field mechanical property mapping with quantitative laser ultrasound visualization system
Authors: Wu Chia-Han , Yang Che-Hua
Published: April 2012

This research employs a quantitative laser ultrasound visualization system (QLUVS) for the full-field mechanical property mapping in plate-like structures. The QLUVS has the advantage of fast, full-field and quantitative inspection. The QLUVS uses a pulsed laser generate acoustic waves with fast scanning mechanism to reach two dimensional scanning goal and then detected with a piezoelectric longitudinal transducer. By utilizing QLUVS, the spatial and temporal information of guided wave can be obtained with further signal processing, the velocity map can be extracted. Finally the analytical model and inversion algorithm will be integrated into QLUVS for the full-field mechanical property mapping purpose.
Broadband propagation and photoacoustic time reversal imaging using k-space methods
Authors: Cox Ben , Treeby Bradley
Published: April 2012

Numerical, time domain, models of broadband acoustic propagation using k-space methods will be described and applied to the problem of image reconstruction in photoacoustic imaging. k-space methods are a subset of time-stepping pseudospectral methods, which use FFTs to calculate field gradients, with an additional correction to make the solutions exact in the homogeneous case. Furthermore, they are closely related to a number of methods in the mathematical, engineering and physical sciences literature, including non-standard finite difference schemes, exponential integrators, wavenumber domain reverse time migration, and wave propagator models developed to solve the time-dependent Schroedinger equation. These connections will be discussed and used to illuminate the advantages of the k-space approach for large scale modelling of broadband acoustic waves. To illustrate the method, a fluid-based k-space model will be applied to the inverse acoustic initial value problem encountered in tomographic photoacoustic imaging. It is well known that this can be solved, in the linear case, using a time-reversed numerical model. Extensions from this basic case to absorbing and non-linear media will be explored.
The perceptual normalization of lexical tones: effects of surrounding tonal context
Authors: Ciocca Valter , Francis Alexander , Eramela Elaine , Yau Teresa Siu Kwan , Shum Wing Man
Published: April 2012

Previous research has shown that the perceptual categorization of a target lexical tone depends on its surrounding tonal context (“tone normalization”). Native speakers have been shown to take into account both preceding and following tonal context in order to carry out the normalization process. The present study focused on the effects of the duration and type of preceding tonal context on tone normalization. Listeners identified the tone of a syllable in final sentence position, as a function of the number of syllables (1, 2, 3, or 4) and of the tone type (level or contour) of a semantically-neutral precursor sentence. The results showed that: 1. The effect of the precursor sentence reached an asymptote once listeners heard two syllables; 2. The tone type of the precursor sentence did not affect performance. This evidence is consistent with a tone normalization process that operates on the basis of a running F0 average of the surrounding tonal context. When tonal context precedes the target tone, the running F0 average is effectively computed over a two-syllable interval.
Central nervous system markers for lexical tone learning
Authors: Wong Patrick C.M.
Published: April 2012

A large degree of individual variability can be observed in language learning in adulthood. This variability is especially prominent in the learning of foreign sounds, including lexical tones. In this presentation, I will report a series of experiments from my research group that examines the central nervous system markers for lexical tone learning success. Our knowledge such as collicular sensitivity to frequency modulation and cortical basis of pitch perception can begin to assist in generating specific hypotheses for these markers. In our experiments, native English-speaking adults learned Mandarin-like tone patterns in a lexical context. Behavioral, electrophysiological, neural hemodynamic (fMRI), and neuroanatomical measures were collected to characterize variability in learning success. Among the markers of success we found were integrity of the frequency following response, activity in the posterior auditory cortex, gray matter volume in the Heschl's Gyrus, and white matter connectivity within the auditory cortex. Some of these markers were used to redesign training in order to optimize learning for all learners, including training strategies such as enhancing auditory pitch cues and reducing trial-by-trial stimulus variability. Taken together, these experiments provide information regarding the neural basis of lexical tone learning and demonstrate the feasibility of using biomarkers for designing training. [Work supported by NIH and NSF]
Acoustic cues for lexical tone perception in hearing-impaired listeners
Authors: Wang Shuo , Xu Li , Dong Ruijuan , Li Jing , Mannell Robert , Zhang Luo
Published: April 2012

This series of studies was aimed to investigate how listeners with sensorineural hearing loss (SNHL) and with auditory neuropathy syndrome disorder (ANSD) achieved lexical tone recognition using either the temporal envelope (E) or the fine structure (FS) cues. Five groups of Mandarin-speaking subjects, including (1) 22 normal-hearing subjects, (2) 8 moderate, (3) 13 moderate to severe, (4) 10 severe SNHL patients with various degrees of SNHL, and (5) 10 patients with ANSD, participated in the study. Monosyllabic words were processed through a 16-channel “auditory chimera” in which E from a monosyllabic word of one tone was paired with FS from the same monosyllable of other tones. On average, 92.0%, 67.4%, 58.1%, 37.5%, and 17.1% of the tone responses were consistent with FS cues, while 5.8%, 23.7%, 31.1%, 45.2%, 42.7% of the tone responses were consistent with E cues for the 5 groups of subjects mentioned above. Therefore, as the hearing loss becomes more severe, the ability of SNHL patients to use FS for tone recognition becomes more deteriorated. The ability of ANSD subjects to use FS is even poorer than patients with severe SNHL even though their pure-tone thresholds were only moderately elevated in the low and mid frequencies.
Cochlear implant users' melody recognition with pitch and loudness cues
Authors: Luo Xin , Masterson Megan , Wu Ching-Chih
Published: April 2012

Normal-hearing listeners can recognize familiar melodies from loudness changes, although more poorly than from pitch changes. Two hypotheses were tested here: (1) cochlear implant (CI) users can also use loudness changes to perceive melodic contours, and (2) their melody recognition can be enhanced with consistent pitch and loudness changes. In Experiment 1, melodic contours were created by changing the F0s of harmonic complex tones, by changing the intensities of broadband noise bursts, or both. In Experiment 2, familiar melodies were recorded by a pianist. The note intensities were kept as recorded, equalized at 70 dB SPL, or changed from 45 to 75 dB SPL to match the relative pitch changes in semitones. Loudness melodies were also generated with intensity-changing noise bursts. The results showed that CI users' melodic contour identification was better with both pitch and loudness changes than with either alone. Specifically, adding loudness changes significantly improved identification of melodic contours with 1-semitone intervals. CI users had similar familiar melody recognition with pitch or loudness changes alone. For all but one subject with the lowest performance, familiar melodies were not better recognized when pitch and loudness changed together, showing a lack of integration between the two cues.
Joint Doppler and time delay estimation by compressed sampling
Authors: Li Xuan , Ma Xiaochuan , Yan Shefeng , Hou Chaohuan
Published: April 2012

Joint Doppler shift and time delay estimation is an important topic in radar, sonar and communication applications. Least square (LS) is a classical and effective method for solving the problem. However, the performance degrades severely in the scenario of low ratio of signal-noise (SNR), due to the instability of matrix inversing. In this paper, a high-resolution method is proposed basing on the compressive sampling theory. The 2-dimension channel response can be sparsely recovered, and high-resolution Doppler shift-time delay estimation can be described with an underdetermined equation solving problem. Three categories of algorithms, including diagonal loading least squares, ℓ1 Regularization, and Greedy Pursuit, are adopt to solve the problem and show outstanding resolving capabilities. The three categories of algorithms are analyzed and compared in different conditions. For the dictionary appears not to have unit norm columns, Greedy pursuit is not good as ℓ1 Regularization in general, and simulation results demonstrate it.
An efficient post-processing filter for multi-channel acoustic echo cancellation system
Authors: Zhang Henglizi , Chen Kai , Lu Jing
Published: April 2012

The acoustic echo usually cannot be totally removed by the adaptive filter due to the insufficient filter taps, nonlinearity of the echo path transfer function, and the background noise. A post-processing filter, which aims to suppress the residual echo, thus plays an important role in the acoustic echo cancellation system. In this paper, an efficient post filter is proposed based on the coherence between the error signal and the echo estimation of the adaptive filter. The proposed method can be seamlessly combined with the multi-delay frequency-domain adaptive filter. Furthermore, it can be easily extended to multi-channel processing. The instrumental evaluation and listening test both demonstrate the superiority of the proposed method.
A study of beamforming in FDTD method to synthesize directional sound for sound field reproduction
Authors: Nakano Kota , Morise Masanori , Nishiura Takanobu , Yamashita Yoichi
Published: April 2012

Sound field reproduction is useful to represent sound contents with high-realistic sensation. We have proposed a sound field reproduction system to control the perceived angles of virtual sound sources. The system synthesizes the propagated sounds by using sound field simulation and multi-directionally represents them with head-enclosed loudspeakers. The multi-directional sound representation requires the sound field simulation to synthesize directional sounds. We therefore focus on beamforming by array processing in finite-difference time-domain (FDTD) method. FDTD is an effective method to simulate sound field. It discretizes the time-space with meshes and defines the distribution of sound pressure level (SPL) by calculation result of the SPL propagation between the each mesh. We accordingly propose a new approach for sound field simulation to synthesize directional sound. In the proposed approach, the beamforming is applied to the SPL propagation between FDTD meshes. The beamforming with FDTD meshes achieves to control the directional characteristics at each mesh for SPL propagation. With the directional characteristics controlled by beamforming, the directional sound is synthesized. According to the evaluation conducted to verify the performance, it was confirmed that the proposed approach enabled FDTD to control the directional characteristics for directional sound synthesis.
A new soft decision feedback equalizer in underwater acoustic communications
Authors: Yang Xiaoxia , Wang Jun , Wang Haibin
Published: April 2012

The tap coefficients of the decision-feedback equalizer (DFE) are associated with the multipath spread of the channel. For the underwater acoustic communication channel, the impulse response often covers tens to hundreds of symbols, requiring at least tens of taps in the feedback filter. Once the incorrect decisions are fed back, the error propagation will be severe. In this paper, we propose a new soft decision equalizer. The expected output symbols of the equalizer will be weighted according to their reliability, and summed up, then the result is fed back. This approach can alleviate the effect of those incorrect symbols. For evaluating the performance of the proposed method, a sea test in shallow water was carried out. The experimental results show that its BER decreases by 50% without channel codec, compared with the conventional DFE. Furthermore, the mean square error can also reduce about 2 dB when the error propagation is severe.
Directional pattern of a cross vector sensor array
Authors: Yang Shi-e
Published: April 2012

The directional pattern of array is a kind of spatial filter for signal processing. For the signal coming from different azimuth can be expressed as a periodic function of, it can be expanded in Fourier series. With the help of a cross vector sensor array, more directional patterns such as quadrupoles and octopoles can be obtained. By solving equations, the first few coefficients of Fourier series can be determined. A combine directional pattern of the vector sensor array, which has a maximum value at the required direction and very small value at other directions, is properly chosen to improve the performance of the final directional pattern. The method of determining virtual directional pattern proposed in this paper greatly reduces calculation quantity rather than full-space scanning.
Research on active detection and direction finding method of autonomous underwater vehicle based on vector sensor
Authors: Ling Qing , Sheng Xue-li , Yuan Yan-yi , Lu Jia , Sun Chun-Yan , Bai Ye
Published: April 2012

To resolve the detection and orientation problem of autonomous underwater vehicle which platform is limited, single vector sensor with orientation ability is selected. The method of detection and bearing estimation based on vector sensor and its performance are researched in this paper. Vector sonar synthetical copy correlator and vector sonar synthetical adaptive correlator are put forward here, which use both pressure and velocity information. The composing principle and realizing method of the two processors above are studied and the processing gain, detecting probability and bearing estimation ability of the two are analyzed in acoustic multi-path condition. The theoretical results simulation and experiments show that all methods studied above have better performance than common copy correlation, and in multipath condition, the vector sonar synthetical adaptive correlation does better than vector sonar synthetical copy correlation in the aspect of processing gain and bearing estimation. Keywords: active detection; direction finding; autonomous underwater vehicle; vector sensor; synthetical copy correlator; synthetical adaptive correlator
improved methods and results of hrbsss for mapping the deep sea bottom
Authors: Liu Xiaodong , Zhu Weiqing , Zhang Fangsheng , Zhang Dongsheng , Xu Gaofeng
Published: April 2012

High resolution bathymetric sidescan sonar (HRBSSS) is designed by the Institute of Acoustic, Chinese Academic of Sciences (IACAS). HRBSSS have used the technique of direction of arrival (DOA) estimation. It can work near the sea bottom and mapping the deep sea bottom, and get the high resolution bathymetry and sidescan map, concurrently. HRBSSSs have been mounted on the DTA-6000 deep towed body (maximum work depth 6000m) and the Jiaolong HOV (maximum work depth 7000m). In order to upgrading the performance of the system, a new method for improving the depth accuracy on the nadir of the vehicle and an error correct method for minimizing the influence of the inconsistency among the channels have been developed by IACAS. With these method, we have got the good survey results on the area of the seamount (>2000m depth) and on the area of the sea plain (>5000m depth) in the Pacific Ocean in 2011. These methods and results will be introduced in this article.
Technical scheme and optimization of precision timing and synchronization for underwater systems
Authors: Chen Yu , Wang Haibin , Chen Xi , Wang Dejun
Published: April 2012

Real time base is one of the key features for underwater systems. However, time bias accumulates inevitably in a long-term unattended underwater system, even if high precision oscillators are used. Since it's difficult for underwater equipments to obtain timing information directly from GPS satellites, there's demanding need for effective ways of timing services. In this paper, a technical scheme based on Precision Time Protocol and virtual instruments is given. Timing and synchronization services are provided from remote time server to underwater systems. Technical optimizations are made considering the requirements of practical applications. The optimized solution has been equipped in a practical system. Experiments show it's easy to implement and with high precision, good stability and efficiency.
Detection of second harmonic components of Lamb waves generated from fatigued magnesium plate
Authors: Fukuda Makoto , Imano Kazuhiko
Published: April 2012

Detections of second harmonic components generated from micro cracks created by fatigue tests using finite amplitude Lamb wave were carried out using double-layered piezoelectric transducer (DLPT) with pulse-echo method. Three pure magnesium (Mg) plates applied to fatigue test were used in this experiment. In received waveforms from the plate had fatigue test of 100,000 and 200,000 cycles, second harmonic components were increased by 6 dB and 10 dB, respectively, compared with in the plate had 0 cycles. Their waveforms and spectra were captured in real time by our DLPT system. Detection of second harmonic component is resulted in the useful tool in evaluating defect in the material.
Line-spectra extraction of ship-radiated noise based on harmonic wavelet
Authors: Wang Lu , Ma Yuanliang
Published: April 2012

The ship-radiated noise line-spectra contain a large number of characteristic information of the ship, which has great significance for detection and classification of underwater targets. This paper presents a method for extraction of the line-spectra of the ship-radiated noise under strong background noise using harmonic wavelet transformation. Harmonic wavelet is a class of wavelet, which has specific expression for the box-like shape of spectrum and frequency-domain continuous distribution. These features make it more accurate in time-frequency positioning with no frequency leakage in the decomposition process which results in ultra-narrow-band and high resolution. Using harmonic wavelet transformation, the ship-radiated noise is decomposed into separate orthogonal frequency bands which are non-redundant and non-leaking. Based on this, the strong background noise can be suppressed and the line-spectra can be extracted in frequency domain and reconstructed in time domain successfully. Simulation and experimental results show that the harmonic wavelet transform is more effective in the background noise suppression, and its ability for weak line-spectra extraction is superior to Fourier analysis and FIR filter methods.
Optimization and limitations of a preconditioned multi-level fast multipole algorithm for acoustical calculations
Authors: Burgschweiger Ralf , Ochmann Martin , Schäfer Ingo , Nolte Bodo
Published: April 2012

The Multi-Level Fast Multipole Method (MLFMM) allows the computation of acoustical problems based on the Boundary Element Method (BEM) where the discretized models of the corresponding structures may consist of a huge number of elements. The required calculation time and the memory requirements are much less when compared with conventional methods because the algorithm uses a level-based composition of the potentials from different point sources to acoustic multipoles, which highly accelerates the computation of the matrix-vector-products required for iterative solvers. A multi-level single-order variation of the algorithm was extended to a multi-level adaptive-order version, which was analyzed and optimized with respect to quality, performance and parallelization issues. The iterative solvers used with the MLFMM will be combined with appropriate preconditioners for reducing the number of iterations and improving the performance. The insights gained will be presented using different test cases and the results achieved will be compared with analytical solutions and results of conventional BEM- and FEM-based calculations.
Controllable fuel cell humidification by ultrasonic atomization
Authors: Sung Chia-Chi , Bai Chang-Yuen , Chang Shao-Jui , Chen Jau-Hong
Published: April 2012

Compared to the conventional bubble type used for PEMFC (proton exchange membrane fuel cell) humidification, ultrasonic atomization has the advantages of smaller size, it is easy to refill and change temperature, and, more importantly, humidity controllability. To improve the performance of the FC, this study developed a unique ultrasonic atomization system, including a gas heating pipe, ultrasonic driving circuit, ultrasonic atomizer, and humidity sensors. The reactant gases used are hydrogen and air. When the reactant gas obtains sufficient heat from the heating pipe and enters the ultrasonic atomizer, gas humidification is increased due to the ultrasonic micro water droplets blending into the gases. The humidity is controllable by adjusting either the heating temperature or driving voltage. The size of the micro water droplets can also be manipulated by adjusting the driving frequency. A higher driving frequency leads to smaller droplet mean diameter, which in turn increases the humidification efficiency. At least 90% relative humidity can be maintained under the condition that the flow rate of anode and cathode's reactant gas is restricted to between 1LPM and 25LPM. Under the same condition, the conventional bubble type can only achieve around 80%.
Single beam acoustic tweezer
Authors: Shung K. Kirk
Published: April 2012

Single beam acoustic tweezer, a distant cousin of optical tweezer, has been recently experimentally validated. A prerequisite of acoustic tweezer as in optical tweezer is a sharply focused beam with a steep intensity variation within the dimension of a particle. As the frequency of an acoustic beam reaches 100 MHz or higher, the beam diameter may approach cellular level allowing acoustic tweezing or trapping of a cell. Recent experimental results have shown that it is possible to trap lipid spheres of 100 μm diameter at 30 MHz and 15 μm diameter leukemia cells at 200 MHz. These results along with the experimental arrangement and potential biomedical applications of acoustic tweezer will be discussed in detail in this paper.
Patient-Specific Induced Pluripotent Stem Cells as a Model for Familial Dilated Cardiomyopathy
Authors: Sun Ning , Yazawa Masayuki , Liu Jianwei , Han Leng , Sanchez-Freire Veronica , Abilez Oscar J. , Navarrete Enrique G. , Hu Shijun , Wang Li , Lee Andrew , Pavlovic Aleksandra , Lin Shin , Chen Rui , Hajjar Roger J. , Snyder Michael P. , Dolmetsch Ricardo E. , Butte Manish J. , Ashley Euan A. , Longaker Michael T. , Robbins Robert C. , Wu Joseph C.
Published: April 2012

Human induced pluripotent stem cells generated from patients with familial dilated cardiomyopathy model cardiovascular disease in these patients.
The NorR Regulon Is Critical for Vibrio cholerae Resistance to Nitric Oxide and Sustained Colonization of the Intestines
Authors: Stern Andrew M. , Hay Amanda J. , Liu Zhi , Desland Fiona A. , Zhang Juan , Zhong Zengtao , Zhu Jun
Published: April 2012

Vibrio cholerae
, the cause of an often fatal infectious diarrhea, remains a large global public health threat. Little is known about the challenges
V. cholerae
encounters during colonization of the intestines, which genes are important for overcoming these challenges, and how these genes are regulated. In this study, we examined the
V. cholerae
response to nitric oxide (NO), an antibacterial molecule derived during infection from various sources, including host inducible NO synthase (iNOS). We demonstrate that the regulatory protein NorR regulates the expression of NO detoxification genes
hmpA
and
nnrS
, and that all three are critical for resisting low levels of NO stress under microaerobic conditions
in vitro
. We also show that
prxA
, a gene previously thought to be important for NO detoxification, plays no role in NO resistance under microaerobic conditions and is upregulated by H
2
O
2
, not NO. Furthermore, in an adult mouse model of prolonged colonization,
hmpA
and
norR
were important for the resistance of both iNOS- and non-iNOS-derived stresses. Our data demonstrate that NO detoxification systems play a critical role in the survival of
V. cholerae
under microaerobic conditions resembling those of an infectious setting and during colonization of the intestines over time periods similar to that of an actual
V. cholerae
infection.

IMPORTANCE
Little is known about what environmental stresses
Vibrio cholerae
, the etiologic agent of cholera, encounters during infection, and even less is known about how
V. cholerae
senses and counters these stresses. Most prior studies of
V. cholerae
infection relied on the 24-h infant mouse model, which does not allow the analysis of survival over time periods comparable to that of an actual
V. cholerae
infection. In this study, we used a sustained mouse colonization model to identify nitric oxide resistance as a function critical for the survival of
V. cholerae
in the intestines and further identified the genes responsible for sensing and detoxifying this stress.
Flow diverters and a tale of two aneurysms
Authors: Kuzmik Gregory A , Williamson Theresa , Ediriwickrema Asiri , Andeejani Ahmed , Bulsara Ketan R
Published: April 2012

Flow-diverting devices offer an exciting alternative for the management of large and giant intracranial aneurysms. However, the risk and mechanism of delayed aneurysmal rupture and hemorrhage following placement of these devices are not clearly understood. Two patients with similar symptomatic giant paraclinoid internal carotid artery aneurysms are described. Both patients were treated with SILK flow-diverting devices. In both patients the SILK device was placed without technical complication. The first patient continued to do well 1 year postoperatively with complete aneurysm occlusion. The second patient had a delayed subarachnoid hemorrhage despite markedly decreased filling of the aneurysm immediately following the procedure. Flow-diverting devices are an exciting technology which provide an alternative treatment modality in the management of giant intracranial aneurysms. However, caution must be exercised as the risks of delayed complications have yet to be fully elucidated. Similar aneurysms may have drastically different outcomes due to the unpredictability of this technology.