非自由声场中的目标声场还原与重建方法研究

发布时间：2018-05-18 23:12

本文选题：近场声全息 + 非自由声场　；参考：《合肥工业大学》2014年博士论文

【摘要】：近场声全息技术是一项具有强大的噪声源识别定位及声场可视化功能的声学前沿技术。使用近场声全息技术既可以重建声源表面声压、法向振速等声学量,对声源进行识别和定位,也可以对声源辐射的声场进行预测,从而为机电产品的噪声控制、低噪声及声质量设计等提供依据。但传统的近场声全息技术对测量环境要求严格,即要求声源全部位于全息面的同一侧、全息面背侧为自由声场。而在实际应用中,通常需要进行现场测量,并且位于全息面背侧的干扰声源常常无法移除,这就限制了近场声全息技术的实际工程应用。目前对于非自由声场中的全息重建问题的解决方法通常是采用声场分离技术作为前处理技术去除来自全息面背侧的干扰声。然而在非自由声场中声场由三部分组成：目标声源在自由声场条件下辐射的声场(自由辐射声场)、来自全息面背侧的干扰声(入射声场)以及背侧干扰声经声源表面散射产生的声场(散射声场)。声场分离技术只考虑了前两种声场,而忽略了背侧干扰声在声源表面产生的散射声场。当干扰声源辐射强度较大时,忽略散射声的影响会导致声场重建失败。为了保证在非自由声场中准确地重建出目标声源辐射的声场,需要寻求一种新的方法,能够保证在重建过程中同时去除来自全息面背侧的干扰声和干扰声在目标声源表面产生的散射声。本文即对这一问题展开研究。针对类平面声源,提出了一种完全适用于非自由声场环境的拓展的平面近场声全息理论。针对类球形声源,提出了一种基于球面波叠加法的自由场还原技术,这一技术能够将目标声源的自由辐射声场彻底从测量的混合声场中还原出来,为进一步进行全息重建提供自由声场条件。为解决任意形状声源的声场重建问题,将等效源法用于自由场还原,并将其用于腔体内主动声源的识别。最后,将质点振速测量引入自由场还原技术,提高了非自由声场中质点振速的重建精度。本文的主要研究工作和成果总结如下：第一章首先简要地回顾了近场声全息技术的发展历程,然后系统地介绍了非自由声场中近场声全息技术的研究现状以及在应用中存在的问题,并在此基础上确定本文的研究内容。第二章推导出了非自由声场中拓展的平面近场声全息公式,将平面近场声全息的应用范围拓展到了非自由声场中。在推导过程中,将干扰声在目标声源表面产生的散射场考虑其中,保证了非自由声场中目标声源自由辐射声场重建的准确性。同时对于重建公式中的奇异性问题提出了解决方法。数值仿真和实验结果证明了该公式的有效性。第三章提出了一种基于球面波叠加法的自由场还原技术。利用该技术可以将目标声源在自由声场条件下的辐射声场从测量的混合声场中还原出来,基于还原的声场还可以进一步实施实现目标声场的重建。另外,还提出了一种最优球面波展开项数选取方法,为该技术的应用提供了保障。数值仿真结果表明,利用该技术可以有效地实现目标声场的还原。同时仿真中还对该技术的适用范围进行了研究。第四章研究了基于等效源法的自由场还原技术。首先详细地介绍了该技术的理论,之后通过数值仿真对三种不同形状的声源进行分析,说明了基于等效源法的自由场还原技术对于声源形状具有极强的适应性。最后将该技术用于腔体内主动声源的识别,仿真和实验的结果证明了利用该技术可以在内场环境中准确地识别主动声源的位置。第五章首先将质点振速测量引入基于等效源法的声场分离技术,并且通过与基于声压测量和等效源法的声场分离技术相比,证明了基于质点振速测量和等效源法的声场分离技术可以获得更高的质点振速分离精度；同时还通过仿真对影响分离精度的参数进行了分析。然后进一步推导出基于质点振速测量和等效源法的自由场还原技术。实验结果表明,采用质点振速作为基于等效源法的自由场还原技术的输入量,可以更好地实现目标声源自由辐射声场的重建。第六章对全文的研究工作进行了总结,提出了需要进一步研究的问题。
[Abstract]:In the field of non - free sound field , the sound field ( free radiated sound field ) radiated from the back side of the holographic surface and the sound field ( scattered sound field ) from the back side of the holographic surface can be removed .

In order to ensure that the sound field radiated by the target sound source can be accurately reconstructed in the non - free sound field , a new method is needed to ensure the simultaneous removal of the interference sound from the back side of the holographic surface and the scattered sound generated by the interference sound on the surface of the target sound source during the reconstruction process .

In the first chapter , the development course of near - field acoustic holography is briefly reviewed , then the research status of near - field acoustic holography in the non - free sound field and the problems existing in the application are introduced .

In the second chapter , the planar near - field acoustic holography formula is derived , and the application range of the planar near - field acoustic holography is extended to the non - free sound field . In the derivation process , the scattering field generated by the interference sound on the surface of the target sound source is considered , and the accuracy of the free radiated sound field reconstruction of the target sound source in the non - free sound field is ensured .

In chapter 3 , a free - field reduction technique based on spherical wave superposition method is proposed . It can be used to restore the radiated sound field of the target sound source under the free sound field from the measured mixed sound field . Based on the restored sound field , the reconstruction of the target sound field can be further implemented . The numerical simulation results show that the method can effectively reduce the target sound field . At the same time , the application scope of the technique is also studied .

In chapter 4 , the free - field reduction technology based on the equivalent source method is studied . Firstly , the theory of the technique is introduced in detail . Then , three different shapes of the sound source are analyzed by numerical simulation , which shows that the free - field reduction technique based on the equivalent source method has very strong adaptability to the shape of the sound source . Finally , the technology can be used in the identification , simulation and experiment of the active sound source in the cavity . The position of the active sound source can be accurately recognized in the inner field environment .

The fifth chapter introduces the technique of acoustic field separation based on the equivalent source method , and proves that the sound field separation technology based on the mass point vibration velocity measurement and the equivalent source method can obtain higher particle vibration speed separation precision compared with the sound field separation technique based on the sound pressure measurement and the equivalent source method .
At the same time , the parameters affecting the separation precision are analyzed by simulation . The free - field reduction technique based on the particle vibration velocity measurement and the equivalent source method is further derived . The experimental results show that the free - field reduction technique based on the equivalent source method is adopted as the input quantity of the free - field reduction technology based on the equivalent source method , and the reconstruction of the free - field sound field of the target sound source can be better realized .

The sixth chapter summarizes the research work of the whole text , and puts forward some problems which need to be further studied .
【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB535

【参考文献】