Continuous acoustic source tracking for tangible acoustic interfaces

The challenge in human computer interaction is to create tangible interfaces that will make digital world accessible through augmented physical surfaces like walls and windows. In this paper, two continuous acoustic source tracking methods are proposed which have the potential to covert a physical object into a tracking sensitive interface. The spatial likelihood method has been used to locate an acoustic source in real time. The source location is obtained from searching the maximum in the likelihood map. The Kalman filter is used to improve the trajectory estimation by predicting the location based on the previous source location and the current measurement of the source location. Finally a Linear Positioning algorithm is proposed for acoustic source tracking. This method is independent on the spatial size of the tangible object and thus applicable on large interactive surfaces without additional computation cost. Promising results have been achieved experimentally for the application of acoustic tangible interfaces.     

A new acoustic emission source location technique based on wavelet transform and mode analysis

For wave propagation in dispersive media, the arrival time of the acoustic emission signal to the sensor is dependent on the setting of the threshold voltage, which results in the inaccuracy of the acoustic emission location. Based on the wavelet transform and the theory of modal acoustic emission, a new method is proposed to improve the accuracy of acoustic emission source location. It is believed that the acoustic emission signal propagation in the structure has the characteristics of multi-mode and dispersion, and the acoustic emission source location should use the arrival time to sensors obtained from the output signals not only at the same mode but also at the same frequency. The wavelet transform is used to resolve the problem. By utilizing the time-frequency data of the wavelet, the frequency-dependent arrival time traveling is easily obtained; by numerical computation of the wave’s propagation in structure, the group velocity of the guided mode is also obtained, therefore the accuracy source location is realized. The acoustic emission source location experiments were conducted in a thin steel plate and results show that the technique is an effective tool for acoustic emission source location. __________ Translated from Chinese Journal of Scientific Instrument, 2005, 26(3) (in Chinese)     

水下声信号的激光干涉测量

为准确测量水下目标的发声频率,在光学暗室下建立了基于激光干涉法探测水下目标的实验系统。当水下声源引起水表面波动时,用激光照射水面,携带声波信息的水面散射光与参考光干涉,利用精密光学测量装置探测光程差的改变,通过数据采集和处理系统从干涉信号的频谱分析图中解调出水下声信号的频率信息。干涉信号的频谱分析图中存在以水下声信号频率为中心的频带,频带宽度与自然水表面波引起的多普勒频移有关。实验结果表明,水下发声目标引起水表面波动的振幅在纳米级,系统可以实时探测出4～15kHz的水下声信号,且测量标准偏差7Hz。该系统可满足水下目标识别技术的实时性、准确性等要求。     

钢板声发射时间反转聚焦增强定位方法

声发射检测方法具有实时动态监测优点,应用越来越广泛,但是对声源的定位始终没有更大的突破。在钢板声发射检测中,提出一种基于时间反转理论的声发射源准确定位的方法。由于声发射检测是一种被动检测技术,结合时间反转聚焦理论,推导出对声源信号实现时间反转聚焦增强处理方法,可增强检测信号中声源幅值,提高信噪比;然后根据声源信号到达时间推算出声源聚焦时刻,利用弹性波传播理论对传感器监测区域重建信号传播波动图,显示出声源位置和区域;最后通过实验测试对该方法进行验证,结果表明该方法能有效提高损伤声源信号的能量,对检测区域的信号重建和定位显示准确地给出损伤声源位置。     

Scanning acoustic microscope for visualization of microflaws in solids

A laboratory scanning acoustic microscope working in a pulsed regime at a frequency of 400 MHz with a resolution of approximately 3 μm for investigation and visualization of flaws and microflaws in surface and subsurface layers in solids is described. Acoustic images of various types of microflaws (micropores and microcracks) are obtained and analyzed; the images contain new information n the degree of microdamage to a material compared to that presented by the light microscopy method.     

一种三维质点振速传感器灵敏度测量方法

一种基于近场声全息技术的质点振速传感器灵敏度测量方法,在没有任何特殊声源或声学设备的前提下,通过测量或重建声场中的声压和法向质点振速来计算声阻抗,实现质点振速传感器的灵敏度测量。将该方法扩展至三维质点振速传感器的灵敏度测量,在测量或重建法向质点振速的同时,也测量或重建切向质点振速,实现三维声阻抗的估算,从而同时测量计算3个方向质点振速传感器的灵敏度,并通过实验验证了所提方法的有效性。     

Study of the possibility of producing a short acoustic pulse using an inductive-resistive circuit connected to the input of a radiator loaded on a solid through a contact layer

A scheme of radiation is considered that consists of a piezoelectric plate with an RL-circuit connected to its input and that is loaded on a solid through a contact layer. A study of the effect that the systems characteristic parameters have on the duration and amplitude of radiated pulses for different wavelengths thicknesses, specific acoustic impedance of the contact layers, and different acoustic loads is performed on the basis of numerical calculations. Concrete estimates are presented that show the use of the optimal (from the viewpoint of the minimum duration of radiated pulses) characteristic parameters of the system to obtain short acoustic pulses over a rather wide range of the contact-layer wave thicknesses is made possible.Translated from Defektoskopiya, Vol. 40, No. 11, 2004, pp. 15–21.Original Russian Text Copyright © 2004 by Konovalov, Kuzmenko.     

非规则结构表面多声源近场声全息方法

为了提高非规则结构表面多声源声场的全息精度,提出基于目标深度识别与球面波叠加逼近的非规则表面多声源近场声全息方法。该方法使用声源空间深度识别理论,确定结构体上各声源的空间位置,在各声源处分别使用球面波的叠加描述空间声场分布,然后结合现有单原点球面波叠加近场声全息法重构声场。为了验证方法的可行性,首先使用所述方法和现有单原点球面波叠加声全息法,分别对径向脉动球与横向振动球组成的不同声场进行全息重构。结果表明,当声源集聚分布时,所述方法与现有方法均能有效全息重构声压分布,重构误差在5%以下;当声源离散分布时,现有方法失效,所述方法能够较准确地给出重构面的声压分布,主要频段内的全息重构误差小于20%。进一步的对比实验表明,在全息重构多扬声器非规则空间分布声场时,使用所述全息方法的重构误差平均下降14.08%,显著提升了多声源非规则空间分布声场的全息精度。     

Enhancing nearfield acoustic holography using wavelet transform

When there are low signal to noise relationships or low coherences between measured pressure and a reference sensor, a pressure field measured and estimated by NAH (Nearfield Acoustic Holography) becomes noisy on the hologram and source planes. This paper proposes a method to obtain the high coherent de-noised pressure signals from low coherent noisy ones by combining a wavelet algorithm with NAH. The proposed method obtains the de-noised field from acoustic fields on a noise source plane reconstructed through backward propagation of NAH. Thus this method does not need high coherent pressure signals on the hologram surface while the conventional nearfield acoustic holography requires high-coherent signals. The proposed method was verified by numerical simulation using noisy signals, composed of original signals and imposed noises distributed on the hologram surface.     

Passive acoustic radiation control for a vibrating panel with piezoelectric shunt damping circuit using particle swarm optimization algorithm

This paper presents a new acoustic radiation optimization method for a vibrating panel-like structure with a passive piezoelectric shunt damping system in order to minimize well-radiating modes generated from the panel. The optimization method is based on an idea of using the p-version finite element method(p-version FEM), the boundary element method(BEM), and the particle swarm optimization algorithm(PSOA). Optimum embossment design for the vibrating panel using the PSOA is first investigated in order to minimize noise radiation over a frequency range of interest. The optimum embossment design works as a kind of stiffener so that well-radiating natural modes are shifted up with some degrees. The optimized panel, however, may still require additional damping for attenuating the peak acoustic amplitudes. A passive shunt damping system is thus employed to additionally damp the well-radiating modes from the optimized panel. To numerically evaluate the acoustic multiple-mode damping capability by a shunt damping system, the integrated p-version FEM/BEM for the panel with the shunt damping system is modeled and developed by MATLAB. Using the PSOA, the optimization technique for the optimal multiple-mode shunt damper is investigated in order to achieve the optimum damping performance for the well-radiating modes simultaneously. Also, the acoustic damping performance of the shunt damping circuit in the acoustic environment is demonstrated numerically and experimentally with respect to the realistically sized panel. The simulated result shows a good agreement with that of the experimental result. This paper was recommended for publication in revised form by Associate Editor Yeon June Kang Jin-Young Jeon received his Ph.D. degree in Mechanical and Aerospace Engineering from Tokyo Institute of Technology in 2005. Dr. Jeon is currently a senior engineer at Digital Printing Division, Digital Media & Communications Business at Samsung Elec-tronics Co., Ltd., Korea. His research interests are the areas of structural-acoustic optimization, sound quality, motion quality, and vibration control.     

An experimental rig for near-bit force measurement and drillstring acoustic transmission of BHA

An experimental rig for near-bit force measurement and drillstring acoustic transmission of bottom-hole assembly (BHA) is designed and implemented to investigate downhole dynamic behaviors of BHA. By using a developed dynamic force sensor device with a four-straight beam strain gauge, the rig can measure axial, lateral forces and torques exerted on simulated drillstring while rotating. For the upward transmission of downhole dynamic force data, drillstring acoustic telemetry method is further analyzed by transient numerical simulation. Considering acoustic signal attenuation and transmissibility, a narrow pulse on-off keyed modulated time-delay signal transmission method is developed. The near-bit force measurement experiments of BHA are performed under different weight on bit loads, deviation angles and drill pipe combinations. The obtained force data are transmitted via acoustic waves propagating along the simulated drillstring. The results show that acoustic transmission rate is approximated 77 bit/s along 6.4-m simulated drillstring under 1-W power excitation in the laboratory.     

双五元十字阵被动声定位融合算法及性能分析

为了提高被动声测量的准确度和克服声源目标空间方位模糊的问题,提出了双五元十字阵被动声定位融合算法。首先设计了一种双五元十字阵传声器阵列模型,依据模型定义了声源点象限判断准则;然后根据被动声定位原理推导了单一五元十字阵的声源点坐标计算公式,根据俯仰角度正弦值作为加权系数,构造了双五元十字阵被动声定位融合算法模型;最后对该模型测距和测向的精度进行了理论分析,给出了时延估计误差、俯仰角以及方位角与双五元十字阵定位性能的关系。理论分析和仿真实验结果表明,该算法克服了声源目标空间方位模糊的问题、减小了时延估计误差对测距测向性能的影响。本文算法能够更加准确地测量出声源点的位置信息。     

Corrected <Emphasis Type="Italic">F</Emphasis> criterion for testing uniformity of samples over variances

A robust method for testing the homoscedasticity of two samples over variances was developed. The computational algorithms were obtained and studied. The criterion was used to process the results of acoustic measurements. Statistical procedures were proposed for introduction into engineering physics experiments.Translated from Defektoskopiya, Vol. 40, No. 10, 2004, pp. 3–12.Original Russian Text Copyright © 2004 by Krivosheev, Ivanov, Gostyushkin.     

传声器阵列函数反卷积声源成像算法研究

反卷积声源成像算法具有较高的空间分辨率,但动态范围不理想导致成像结果中存在虚假声源。针对此问题,提出函数反卷积声源成像算法,利用函数波束形成算法改进成像性能,通过对反卷积声源成像算法中的点扩散函数进行幂次运算,建立函数波束形成输出功率、升幂点扩散函数与声源分布之间的线性关系,形成函数反卷积声源成像算法方程组;进一步采用正约束的高斯-赛德尔迭代方法,求解声源分布信息。对单声源和非相干声源仿真与实验表明,与函数波束形成、反卷积声源成像算法相比,所提出算法可有效改善成像分辨率及动态范围。根据声学中心覆盖面积随幂指数的变化关系,建议算法中幂指数取值范围为6～14。     

无须测量声速的声发射源定位方法研究

为消除声速测量偏差给声发射系统带来的定位误差，本文提出一种多探头定位方法。从理论上导出了该方法的线定位和平面定位计算公式，并用AE21C型四通道声发射仪在碳钢管道和平板上以铅笔芯折断产生信号为模拟源进行了实验验证，结果表明用这种新的方法具有较高的定位精度，且定位时只要利用原系统的门槛跨越技术测量各探头接收到信号的时差即可，不必测量传声媒质的声速。     

Use of the acoustic emission method in detecting the fracture process in specimens made of composite materials

Experimental results on the localization of acoustic emission (AE) signals obtained in stress-cycling tests of specimens made from the Organit-10T composite material (CM) are considered. The technique developed for collecting prompt information on the changes in the shape of the AE amplitude distribution is analyzed. This distribution characterizes the flow of arriving signals and allows one to determine the beginning of destruction for CM specimens.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 34–41.Original Russian Text Copyright © 2004 by Stepanova, Lebedev, Kareev, Chaplygin, Katarushkin.     

Deformation stage for quantitative acoustic emission measurements

A deformation stage capable of fully reversed fatigue loading for use in the scanning electron microscope (SEM) is described. This stage incorporates a novel surface displacement transducer for the detection of acoustic emission (AE) signals, which has a flat response over a wide band and can be used as a receiver up to 12 MHz. Also described is a method for analysis of these signals to obtain the size, speed, and location of the source event. A special grip geometry is introduced such that the dynamic Greens function describing the surface displacement at the transducer contains an initial p-wave delta function which is utilized to determine the source properties.     

基于声发射和神经网络的风机叶片裂纹识别研究

提出一种对风力机叶片裂纹声发射信号进行模式识别的方法。该方法以叶片无裂纹、萌生裂纹、扩展裂纹和断裂四个阶段为声发射源的四个模式,基于声发射信号含有丰富的发射源信息的特点,通过大量采样获得叶片裂纹声发射信号参数,并依照叶片裂纹声发射参数分析的数值特点确定BP神经网络,用选定的网络对叶片裂纹阶段进行模式识别,以判断裂纹的危害程度。仿真结果表明,利用BP神经网络可以对声发射信号进行有效识别,识别准确率达到90%以上。     

基于智能手机TDOA估计的被动声源定位方法与系统实现

被动目标监测广泛应用于国防、安全等领域。针对被动声目标监测,首次提出了基于手机平台的被动式声目标定位方法,并设计和开发了原型系统。针对手机间时钟同步对被动式信号到达时间差精度的影响,采用手机内置的麦克风和扬声器发送和接收同步声信号的方式,从而避免了节点间无线同步到声信号采集间的时间延迟不确定性。为了提高信号发送和接收时刻的估计精度,将时间戳信息调制到设定的线性调频声信号,并采用广义互相关方法来实现信号波形检测。进一步,针对被动目标声源的非合作特性,采用统计判决理论和语音活动性检测相结合的方法对观测信号进行联合检波,获得被动目标声源到达时间的高精度估计,即被动声源到手机间的到达时间差。最后,通过多部手机搭建了原型系统并设计实验,结果表明定位误差不超过10%的概率达到80%。     

针对不连续带洞结构的声发射源定位方法研究

由于兰姆波在舷窗等带孔结构表面的传播路径不再是线性路径,传统方法难以解决撞击的声源定位问题。 本文针对该 问题,提出了一种基于声发射的网格映射概率成像定位方法。 该方法通过建立网格映射模型解决了信号传播的非线性路径难 题,并通过对网格节点的信号最快传播路径计算得到相应的理论时间差值。 之后利用自适应能量阈值方法与 AIC 方法计算信 号的实际到达时间差,通过比较理论值与实际值的偏差构建概率图像以实现定位解算。 通过有限元模拟分析了带洞结构对兰 姆波传播路径的影响,给出信号传播路径的确定依据。 通过对 32 个撞击点的定位实验验证了定位方法的可行性,平均绝对误 差为 1. 15 cm。