【作者】 张小正；

【导师】 毕传兴；

【作者基本信息】 合肥工业大学 ， 机械设计及理论， 2012， 博士

【摘要】 近场声全息技术(NAH)是近二十多年来发展起来的一种具有强大的噪声源识别定位和声场可视化功能的声学前沿技术,它可以为产品的噪声控制、低噪声及声质量设计等提供重要依据。目前,国内外学者提出了多种全息算法,然而这些算法大多在频域内进行,且只适用于稳态声场。在实际工程中,很多情况下声场为瞬态声场,若将NAH应用到瞬态声场,获得声场随时间的变化规律,必将极大地扩展其工程应用范围。正是在这一背景下,瞬态近场声全息(TNAH)被提出来。本文在分析TNAH的研究意义和研究进展的基础上,将已有的TNAH按照全息面声压信号处理方式的不同分为四类：基于三维变换的TNAH、基于二维变换的TNAH、基于一维变换的TNAH和无需变换的TNAH。本文对这四类TNAH中存在的问题进行了深入地研究和探讨,并提出了相应的解决方法。在基于三维变换的TNAH研究中,提出了基于Laplace变换的瞬态声场质点振速重建方法,用于解决基于Fourier变换的时域声全息在重建质点振速时出现的奇异性问题；在基于二维变换的TNAH研究中,推导出全息面声压到重建面质点振速之间的脉冲响应函数,并结合实时声全息的思想提出了基于该脉冲响应函数的质点振速重建方法；在无需变换的TNAH研究方面,提出了两种新的全息方法：基于时域平面波叠加法的TNAH和基于插值时域等效源法(ESM)的TNAH;最后提出一种瞬态声场分离方法,实现了TNAH在非自由声场条件下的运用。本文具体研究内容如下：第一章首先阐述了TNAH的研究意义,然后通过论述国内外有关瞬态声辐射计算的研究进展为TNAH的研究提供借鉴和思路,最后通过回顾目前国内外已有的TNAH方法,并分析其存在的问题,确立了本文的主要研究内容。第二章研究了基于三维变换的时域声全息。首先推导了基于Fourier变换的时域声全息的声压重建公式,并从理论上分析了声压重建过程中的误差及其控制办法。为了解决基于Fourier变换的时域声全息在重建质点振速时出现的奇异性问题,提出了基于Laplace变换的瞬态声场质点振速重建方法,并通过以固定在障板上的活塞为声源的数值仿真验证了所提出方法的有效性。第三章分析了基于二维变换的实时声全息。首先从速度势波动方程和Neumann边界条件出发,运用Laplace变换推导了全息面声压到重建面声压之间的脉冲响应函数,并阐述了基于该脉冲响应函数的声压重建过程。为了能够实现声场中质点振速的实时重建,运用Laplace变换推导了全息面声压到重建面质点振速之间的脉冲响应函数,并结合实时声全息的思想提出了基于该脉冲响应函数的质点振速重建方法,最后通过以障板上的圆形活塞为声源的数值仿真检验了该方法的有效性。第四章基于波叠加法的思想,提出了两种无需对全息面声压进行任何变换的TNAH:基于时域平面波叠加法的TNAH和基于插值时域ESM的TNAH。两者均避开了二维空间Fourier变换的使用,从而避免了二维空间Fourier变换所带来的限制；而且两者的重建过程均在时域内进行,因而具有实时重建声场的能力。首先推导了基于时域平面波叠加法的TNAH的重建公式,详述了其重建过程,并通过数值仿真和实验验证了其有效性,进一步与时域声全息和实时声全息相比较阐述了其优越性。随后推导了基于插值时域ESM的TNAH的重建公式,阐述了其重建过程,并通过三例具有不同形状声源的仿真阐述了该方法不仅具有TNAH常规的功能,而且不受声源形状的限制,因此该方法具有更加广阔的应用范围。第五章将TNAH扩展到非自由声场。首先基于声波在时域波数域的传播原理,推导了瞬态声场分离公式,提出了一种适用于非自由声场条件下的瞬态声场分离方法。该方法不仅可以在空间域,而且可以在时域,很好地移除干扰声源的影响,分离出只有目标声源辐射的声场；继而可以将分离出来的目标声源辐射声场与TNAH联合起来,实现非自由声场条件下的声场重建。第六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), developed in recent over20years, is an advanced acoustic technique with the powerful abilities of identifying noise sources and visualizing sound fields. It can provide the important guidance for the noise control, as well as the low-noise and sound quality design of product. Up to now, the domestic and foreign scholars have proposed a number of holography methods. However, these methods almost proceed in the frequency domain, and are only applied to stationary sound fields. In practice, sound fields are usually transient. If the NAH is used in transient sound fields to obtain the varying patterns of sound fields with time, it will be applied to the engineering more widely. Therefore, transient nearfield acoustic holography (TNAH) is developed. On the basis of analyzing the research significance and development of TNAH, it is divided into four kinds in accordance with the processing mode of pressure signals on the hologram surface:TNAH based on three-dementional transform, based on two-dementional transform, based on one-dementional transform, and without any transform.In this dissertation, problems existing in these four kinds of TNAH were investigated and discussed deeply, and then the corresponding solutions were provided. In the research of TNAH based on three-dementional transform, a method based on the Laplace transform for reconstructing the particle velocity in transient sound fields was proposed to solve the singularity appeared in time domain acoustic holography with the Fourier transform. In TNAH based on two-dementional transform, the impulse response function between pressure on the hologram surface and particle velocity on the reconstruction surface was deduced, based on which real-time acoustic holography processed the ability of reconstructing particle velocity. With respect to TNAH without any transform, two new approaches were presented:one is based on time domain plane wave superposition method, and the other adopted an interpolated time-domain equivalent source method (ESM). To realize the use of TNAH in nonfree sound fields, a separation technique of transient sound fields was developed. The detailed research contents of this dissertation are summarized as follows:In chapter one, the significance of TNAH was first elaborated, and then the development of calculating transient acoustic radiation at home and abroad was discussed to provide references and ideas for TNAH, finally by reviewing existing approaches of TNAH and analyzing their defects, the main research contents of this dissertation were determined.In chapter two, time domain acoustic holography based on three-dementional transform was investigated. Its reconstruction formulas of sound pressure were deduced based on Fourier transform, and its reconstruction errors as well as the corresponding control methods were analyzed in theory. To solve the singularity appeared in the process of reconstructing the particle velocity by time domain acoustic holography based on the Fourier transform, a method using the Laplace transform was proposed, whose validity was also confirmed by a numerical simulation with a baffled piston as source.In chapter three, real-time acoustic holography based on two-dementional transform was analyzed. The impulse response function between sound pressure on the hologram plane and sound pressure on the reconstruction plane was first deduced by Laplace transform from the wave equation of velocity potential and Neumann boundary condition, and then based on it the reconstruction process of sound pressure was shown. To reconstruct the particle velocity in real time, the impulse response function between sound pressure on the hologram plane and particle velocity on the reconstruction plane was also deduced by Laplace transform, and then based on it a reconstruction method of particle velocity using real-time acoustic holography was proposed and verified by a numerical simulation with a baffled circular piston as source.In chapter four, two approaches of TNAH without any transform were proposed by using the wave superposition idea:one is based on time domain plane wave superposition method, and the other based on an interpolated time domain ESM. They both avoided the use of two-dementional spatial Fourier transform, thus removing restrictions brought by two-dementional spatial Fourier transform. Besides, their reconstructions were proceeding in the time domain, which provided the ability of reconstructing sound fields in real time. The formulas of TNAH based on time domain plane wave superposition method were first deduced, and then its reconstruction process was elaborated, finally its validity and advantages were demonstrated respectively by numerical simulations and experiments, and by comparisons with time domain acoustic holography and real-time acoustic holography. Similarly, the formulas of TNAH based on an interpolated time domain ESM were deduced, and its reconstruction process was elaborated. Three simulation cases with different shape sources were carried out to demonstrate that TNAH based on an interpolated time domain ESM not only processed conventional abilities of TNAH, but also got rid of the limit from source shapes, thus having more wide application range.In chapter five, TNAH was extended to the nonfree sound fields. In the case of nonfree sound fields, a transient sound field separation technique was first developed to remove the influence of disturbing sources and separate out the sound field only radiated by objective sources in both time and space domains, and its separation formulas were deduced based on the propagation principle of sound pressure in the time-wavenumber domain. Then by utilizing the separated sound field radiated by objective sources and combining TNAH, the reconstruction could be realized in the case of nonfree sound fields.In chapter six, all the investigations in this dissertation were summarized, and the topics studied further in the future were proposed.更多还原