近场声全息中误差分析及正则化研究
文献类型：学位论文
| 作者 | 李凌志 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-31 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 近场声全息 误差分析 逆问题 正则化 声源识别 |
| 其他题名 | The error analysis and regularization methods in nearfield acoustic holography |
| 学位专业 | 声学 |
| 中文摘要 | 近场声全息是一种实用的声场重建和预测的方法。它可通过声源辐射体附近一个平面上有限位置处的声压重建和预测出整个空间的声压、质点振动速度和声强等一切声学量。由于具有非接触式测量、重建分辨率高、重建声学量全等优点，近场声全息方法在声源识别及故障诊断中得到了广泛的应用。近场声全息的逆向重建过程是离散线性病态逆问题，必须进行正则化处理。当全息面边缘的声压存在较大的变化时，常用的Tikhonov正则化方法总是得到不稳定甚至错误的结果。针对这一问题，本文提出并完成以下工作。 （1）对基于Tikhonov正则化方法的三种正则化参数选择方法，即离差原理法、广义交叉验证法、L曲线法，在不同全息距离、声源频率和信噪比的条件下进行了比较。结果表明，它们在较远全息距离及低噪声环境下难以获得合适的正则化参数。采用等效噪声方差的方法，提出了一种改进的离差原理法。 （2）分析了当全息声压误差为空间无关高斯白噪声时全息声压和重建声压之间的均值和方差的关系，得到了一个关于重建面和全息面声压能量的简单的统计能量约束方程。利用这个约束方程，得到了一种新的正则化方法。这个方法可以在没有任何预先的噪声信息的条件下稳定快速地确定优化的正则化参数。 （3）数值仿真和实验表明，本文所提出的改进的离差原理法和基于统计能量约束方程的正则化方法在很宽的信噪比范围(>6dB)和相对更远的全息距离条件下均能得到合适的正则化参数，并且能稳定快速地重建出所需的声学量。因为这两种方法无须对全息声压进行加窗平滑处理，所以能保证有效重建孔径和全息孔径相等。 |
| 英文摘要 | Nearfield acoustic holography (NAH) is a useful method for reconstructing and predicting sound pressure, particle velocity and sound intensity in the entire sound field on the basis of the hologram sound pressure in the nearfield of a radiator. Owing to its non-contact nature, high resolution and completeness, NAH has been widely applied in sound source identification and fault diagnosis. The reconstruction of NAH is a linear, ill-posed inverse problem, in which a regularization procedure must be used. However, the popularly used Tikhonov regularization procedures always lead to inconsistent or even erroneous results when the hologram has a large edge discontinuity. In this thesis three issues in NAH are addressed. (1) Three Tikhonov regularization based parameter selection methods, Morozov Discrepancy Principle method (MDP), Generalized Cross Validation method (GCV), and L-curve method, are compared at various hologram distances, sound source frequencies, and Signal-to-Noise Ratios (SNR) . The results show that none of them is reliable at large hologram distances and low noise conditions. Based on an equivalent-noise-variance method, we established an improved MDP method. (2) We analyzed the relationships between the measured hologram and reconstruction sound pressure in terms of mean value and variance for planar NAH, and found that when the measured noise is spatially uncorrelated and randomly distributed, a simple statistical energy constraint equation (SECE) linking the energy of reconstruction and hologram planar sound pressure variance can be obtained. A fast and robust regularization procedure, which is able to find the optimal regularization parameter without any prior knowledge of the noise, is developed for planar NAH on the basis of the SECE. (3) Numerical simulations and experiments proved that the improved MDP method and the SECE based regularization procedure are robust in locking proper regularization parameters over a large SNR range (>6 dB) and at a relatively larger hologram distance. In these two methods the valid reconstruction aperture is equal to the hologram aperture because there is no need to smooth the hologram pressure. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 145 |
| 源URL | [http://159.226.59.140/handle/311008/440]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 李凌志. 近场声全息中误差分析及正则化研究[D]. 声学研究所. 中国科学院声学研究所. 2009. |
入库方式： OAI收割
来源：声学研究所
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