【作者】 张永斌；

【导师】 陈心昭；

【作者基本信息】 合肥工业大学 ， 机械电子工程， 2010， 博士

【摘要】 近场声全息(NAH)是一种先进的用于声源识别、定位以及空间声场可视化的噪声测量分析前沿技术。该技术已经用于船舶、汽车和家电等各个行业,也逐渐成为这些行业解决环境和产品噪声问题的强有力的工具。本文在深入分析NAH技术的发展历程和最新进展的基础上,从重建算法、正则化、测量方法和前处理四个关键环节对NAH技术中仍然存在的问题进行了深入的研究和探讨。在重建算法上,将基于等效源法(ESM)的NAH技术扩展到非闭合声源和移动声源辐射声场的重建和预测,拓宽了NAH技术的应用范围;在正则化技术上,为克服L曲线法的缺陷,提出一种更加稳定的正则化参数选取方法;在测量方面,将基于Microflown传感器的质点振速测量方法引入NAH技术中,以解决声源表面法向振速重建困难的问题,并分别基于空间Fourier变换和ESM算法对该测量方法的优越性进行了验证;在前处理技术方面,提出了分别基于空间Fourier变换和统计最优方法的两种新型单面声场分离技术,提高了测量效率和声场分离精度;对汽车车厢内部声场开展实验研究,基于前文提出的声场分离技术和质点振速测量方法实现了内声场中的声源识别和声场可视化,为NAH技术进一步应用于工程实际打下基础。本文具体研究内容主要围绕ESM(第二、三章)和质点振速测量方法(第四、五、六章)展开,结构安排如下:第一章从重建算法、误差分析、滤波和正则化技术、以及最新进展等几个方面详细地介绍了NAH技术的发展历程和研究现状,探讨了目前NAH技术中仍然存在的问题,并确立了本论文的主要研究内容。第二章从理论上将基于ESM的NAH技术扩展到非闭合声源情况,为基于ESM的Patch NAH技术的研究打下基础;首次提出一种基于ESM的移动声源辐射声场计算方法——移动等效源法;为解决任意形状移动声源的NAH重建和预测,首次提出基于移动等效源的NAH技术;数值仿真和对点激励固支板辐射声场的实验研究验证了所提出扩展理论的正确性和有效性。第三章在基于ESM的NAH技术基础上深入分析应用L曲线法有时出现正则化参数错误选择或不当选择的原因,提出一种新的正则化参数选取方法—| cosθ|曲线法,有效地解决了L曲线法存在的问题;对简支板和振动球的数值仿真,以及对固支板、箱体和双音箱三种不同声源的实验研究验证了所提出方法的有效性以及相比L曲线法的优越性。第四章简要介绍了Microflown质点振速传感器的原理及其在声学领域的应用;提出了基于质点振速测量的常规NAH和迭代Patch NAH技术,有效地解决了声源表面法向振速重建的困难;对质点振速—声压重建过程中的奇异性问题进行分析,推导出等效替代的传递因子,保证了质点振速测量在基于Fourier变换的NAH技术中的成功应用;数值仿真和对实际声源的实验研究验证了所提出方法的有效性和正确性,同时也表明质点振速更适合作为Patch NAH技术的输入量。第五章将质点振速测量方法引入基于ESM的常规NAH和Patch NAH技术,以解决任意形状声源表面法向振速重建困难的问题;分别基于声压和质点振速两种测量方法对NAH重建过程进行了误差灵敏度分析,从理论上说明以质点振速为输入量的基于ESM的NAH技术的重建稳定性要好于声压测量;利用质点振速的矢量特性,提出基于声压—质点振速测量的p-u声场重建方法,用于消除反射声或消除与声源关于全息面处于对称位置的干扰声源的影响;数值仿真和对不同声源的实验研究验证了质点振速测量在基于ESM的NAH技术中的优越性,也验证了p-u声场重建方法的可行性和有效性。第六章分析了基于Fourier变换的双面和单面声场分离技术中存在的问题;提出了基于Fourier变换的修正的单面声场分离方法;为进一步减小Fourier变换算法引入的各种误差,提出了基于统计最优NAH的新型单面声场分离技术,提高了测量效率和声场分离精度;数值仿真和多种情况下的实验研究验证了所提出的两种分离方法的有效性和正确性,并通过互相比较说明了各自的优缺点。第七章以汽车车厢内声场为例进行了实验研究,采用质点振速测量方法、基于ESM的Patch NAH和声场分离技术在车内声场中成功地实现了声源识别和声场可视化,为NAH技术在封闭空间内声场中的应用打下基础,对于NAH技术的进一步推广具有重要的意义。第八章总结了本文的主要研究成果,提出了需要进一步研究和解决的问题。更多还原

【Abstract】 Nearfield acoustic holography (NAH), which can be used to identify sound sources and to visualize sound field, is an advanced technique for the analysis and measurement of sound. It has been introduced into the industries of ship, vehicle, and home facility, and gradually becomes one of the most powerful tools for dealing with the noise problems of products of these industries. In this dissertation, after reviewing the development and the recent achievement detailedly, NAH technique was further investigated in view of four key processes, including reconstruction algorithm, regularization, measurement, and preprocess. The investigation on the reconstruction algorithm is that the NAH based on the equivalent source method (ESM) was extended to the application in unclosed sound sources, and in moving sound sources. In the field of regularization, a stabler method for the choice of regularization parameter was proposed in order to overcome the limitation of the L-curve method. A new measurement method using Microflown transducers was introduced into NAH, by which the particle velocity was measured instead of the pressure, and better reconstruction of normal velocities on the surface of sound sources could be obtained. Besides, the superiority of particle velocity measurement in the NAH was examined based on the Fourier transform and on the ESM, respectively. Two novel techniques for sound field separation were proposed based on the Fourier transform and on the statistically optimized method, respectively, by which the measurement becomes more effective, and the separation precision becomes higher. Some experimental investigations were carried out with the inner field of a car based on the proposed methods, such as sound field separation and particle velocity measurement. The results demonstrated that the NAH technique was implemented successfully in the inner field. The main contents of the dissertation can be divided into two parts, one (Chapters 2 and 3) concerned the NAH based on the ESM, whereas the other (Chapters 4, 5 and 6) concerned the NAH based on the measurement of particle velocity. The detailed arrangement of the dissertation is summarized as follows:In chapter one, the development history and the current status of NAH were reviewed detailedly from the points of reconstruction algorithms, error analysis, filter and regularization, and recent achievement. Then problems still existed in NAH were discussed, and the main research contents of this dissertation were determined.In chapter two, the NAH technique based on the ESM was extended to the case of unclosed sound sources, which provides a basis for the Patch NAH based on the ESM. A moving ESM was firstly proposed to calculate the sound field radiated from moving sources with arbitrary shape. By applying the moving ESM to NAH, the reconstruction and prediction of the field generated by arbitrarily shaped sources were realized. The validity of the proposed theory in this chapter was demonstrated by numerical simulation and by the experiment carried out with a clamped plate excited at its centre.In chapter three, the reason why the regularization parameter was wrong or improperly chosen in NAH based on the ESM, was deeply analyzed. Then a new method, called | cosθ| curve, was proposed for the choice of regularization parameter, which dealt with the limitation of the L-curve method. The validity and the superiority of the proposed method was proved by numerical simulations of simply supported plate and oscillating sphere, and by experiments carried out with clamped plate, box, and double speakers.In chapter four, the particle velocity transducer named Microflown was simply introduced from its principle and its application in the field of acoustics. In order to improve the reconstruction of normal velocities on the surface of sound sources, both conventional and Patch NAH techniques were proposed based on the measurement of particle velocity. The singularity in the process of velocity-pressure reconstruction was analyzed first, and then was eliminated by a deduced equivalent formulation, which guaranteed the successful application of particle velocity measurement to the NAH based on Fourier transform. The correctness and the validity of proposed method were verified by the numerical simulation as well as the experiment, and a conclusion that the particle velocity is more suitable as an input of Patch NAH was also demonstrated.In chapter five, the measurement of particle velocity was introduced into the conventional and the Patch NAH based on the ESM to enhance the reconstruction precision of normal velocities on the surface of sound sources with arbitrary shape. By error sensitivity analysis, it was shown in theory that NAH based on the ESM is stabler when it was from particle velocity measurement. Because the particle velocity is a vector, a p-u method can be obtained by combined measurement of pressure and particle velocity, which can eliminate the reflection and the influence from the disturbed sources on the opposite side of the holographic surface. The conclusions in this chapter were demonstrated by numerical simulations and experiments carried out with different actual sources.In chapter six, the existed problem in the current sound field separation techniques was analyzed first, and then an improved separation method was proposed based on the Fourier transform and on the measurement in a single surface. In order to reduce the errors from the Fourier algorithm, a new separation technique was further proposed based on the statistically optimized NAH, by which the measurement efficiency and the separation precision were enhanced. The validity and correctness of the two proposed separation techniques were verified by numerical simulation and experiments in different cases. Finally, the advantage and the disadvantage of these two proposed methods were illuminated through the comparison between them.In chapter seven, a practical experiment was carried out in the inner field of a car. The methods of particle velocity measurement, the sound field separation, and the Patch NAH based on the ESM were successfully applied to identify the noise source and to visualize the sound field in the inner field. The result of the experiment provides a basis for the application of NAH to the inner sound field, and it is significant to the spread of NAH.In chapter eight, all the investigations in this dissertation were summarized, and the topics studied further in the future were proposed.更多还原