共查询到19条相似文献,搜索用时 312 毫秒
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在近场声全息技术的基础上,研究了基于声压-质点振速测量的单面声场分离技术.分析了现有基于Fourier变换的单面声场分离技术中的奇异性问题,并应用波数域谱平均法提出了去除奇异性的修正声场分离公式.为改善分离效果,减小由于Fourier变换引起的卷绕误差等因素的影响,基于统计最优近场声全息提出了一种新的单面声场分离方法.通过仿真分析对各种单面声场分离方法做了比较,并用Microflown公司的声强探头做了基于声压-振速测量的单面声场分离实验研究,验证了提出的修正公式和基于统计最优单面声场分离方法的正确性和有效性.
关键词:
声场分离
近场声全息
统计最优
Fourier变换 相似文献
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提出空间声场分离技术,突破了近场声全息(NAH)的应用局限.它们的局限在于全息面一侧的声场必须是自由声场,即要求所有的声源必须位于另一侧.利用波数域内的波场外推理论及声压的标量叠加原理,建立起声场分离技术的双全息面实现方法,利用波数域内的Euler公式及粒子振速的矢量叠加原理,建立起该技术的单全息面实现方法.该技术的一个突出优点是在具有背景噪声的全息测量情况下, 可以消除背景噪声对全息变换结果的影响.理论的推导表明该技术方法的正确性,而仿真算例和实验则显示该技术的可行性和有效性.
关键词:
声全息
波数域
声场分离
背景噪声 相似文献
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常规的近场声全息均是采用全息面声压或质点振速作为输入量求解,由于采用单一输入量无法分离来自全息面背向声波的干扰,因此要求所有声源均位于全息面的同一侧,即测量声场为自由声场,这种要求大大限制了近场声全息的实际应用.基于声压-速度测量的近场声全息以全息面上声压和质点振速同时作为输入量,通过建立和求解两侧声源在全息面上的声压和质点振速耦合关系,可以实现全息面两侧声波的分离,从而解决上述问题.文中在前期对声场分离技术研究的基础上,基于欧拉公式和有限差分近似,推导了新的基于声压-速度测量的平面近场声全息理论公式.随后通过实验检验了该方法在有背景源干扰情况下实现声场分离和重建的有效性. 相似文献
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双全息面分离声场技术及其在声全息中的应用 总被引:5,自引:1,他引:5
提出双全息面分离声场技术,克服以往近场声全息(NAH)和基于声强测量的宽带声全息(BAHIM)的应用局限。以往方法的局限在于:全息面一侧的声场必须是自由声场,即要求所有的声源仅能位于全息面的另一侧;而在实际测量的情况下,这个要求是很难达到的。本文提出的声场分离技术利用波场的外推理论,建立起在波数域声场分离的公式,然后通过二维Fourier逆变换,便得到了全息面一侧声源产生的声压,从而达到声场分离的目的。原理的推导理论上论证该技术正确性,数值仿真显示了方法的可行性和有效性。 相似文献
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Planar near-field acoustical holography in a moving medium 总被引:1,自引:0,他引:1
Near-field acoustical holography (NAH) is a well-established method to study acoustic radiation near a stationary sound source in a homogeneous, stationary medium. However, the current theory of NAH is not applicable to moving sound sources, such as automobiles and trains. In this paper, the inclusion of a moving medium (i.e., moving source and receiver) is introduced in the wave equation and a new set of equations for plannar NAH is developed. Equations are developed for the acoustic pressure, particle velocity, and intensity when mean flow is either parallel or perpendicular to the hologram plane. If the source and the measurement plane are moving at the same speed, the frequency Doppler effect is absent, but a wave number Doppler effect exists. This leads to errors when reconstructing the acoustic field both towards and away from the source using static NAH. To investigate these errors, a point source is studied analytically using planar NAH with flow in one direction. The effect of the medium moving parallel to the hologram plane is noted by a shift of the radiation circle in wave number space (k-space). A k-space Green's function and a k-space filter are developed that include the effects of the moving medium. 相似文献
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When performing holography measurements over a limited area of a source, the hologram pressure typically remains finite at the edge of the measurement aperture. Patch near-field acoustical holography (NAH) has been developed specifically to mitigate the effects related to that windowing. In iterative patch NAH, the source distribution is reconstructed in two steps: first, the partially measured sound field is extended iteratively, and then the extended pressure is projected onto the source surface by using conventional NAH procedures. In the present work, a one-step procedure for performing that combined task is described. In this approach, the acoustical property to be reconstructed on a surface of interest is related to the partially measured pressure on the hologram surface in terms of sampling and bandlimiting matrices, and the reconstructed result is obtained by finding the regularized least squares solution of the latter relation; a procedure for determining the cutoff wave number of the bandlimiting matrix without a priori knowledge of the signal bandwidth is suggested. The proposed procedure was validated by using a synthetic sound field created by a point-driven, simply supported plated. 相似文献
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Prager J 《The Journal of the Acoustical Society of America》2007,122(4):2067-2073
This paper presents an investigation of the reconstruction of sound field parameters close to the surface of arbitrarily shaped sound sources. The field is reconstructed using nearfield acoustical holography (NAH) in spherical coordinates. Of particular interest are source shapes where the Rayleigh hypothesis is violated. To overcome the limitation of the minimal sphere given by the validity restriction of the Rayleigh hypothesis an algorithm is proposed for extracting local information from the nonconvergent NAH solution. For the assessment of the results an appropriate virtual test rig is developed employing the Kirchhoff-Helmholtz integral theorem. 相似文献
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To realize the accurate reconstruction of sound field in a moving medium under the condition of limited holographic aperture, a patch nearfield acoustic holography (NAH) in a moving medium is proposed. The proposed method not only reduces the influence caused by the limited aperture effects through sound field extrapolation, but also perfectly suits for sound field reconstruction in a moving medium by improving the shape of the modified Tikhonov regularization filter and the noise estimation method in accordance with flow effects. In the method, two cases that the flow direction is parallel to and perpendicular to the hologram surface are considered. Especially in the perpendicular case, the expression of the wavenumber component in the z direction is improved to make the proposed method suitable for the moving medium at a high Mach number. Simulations are investigated to examine the performance of the proposed method and show its advantages by comparing with NAH in a moving medium and the conventional patch NAH. It is found that, the proposed method is effective and robust at different flow velocities of the medium and different frequencies of the sound source. 相似文献
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The sound-field of a Caribbean low tenor steelpan is examined using nearfield acoustical holography (NAH). The particular instrument, a Bertrand Kelman low tenor, has been previously examined in a single plane using a four microphone sound intensity technique. This paper will examine the sound radiation in a cuboid space enclosing the instrument at three frequencies. Presented will be the results of sound pressure level (SPL), active acoustic intensity (AI), and reactive acoustic intensity (RI) obtained through application of the NAH technique. The limitations of NAH when applied to an irregularly shaped object such as a tenor steelpan will also be presented. 相似文献
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HU Bo YANG DeSen SHI ShengGuo & SUN Yu Science Technology on Underwater Acoustic Laboratory Harbin Engineering University Harbin China 《中国科学:物理学 力学 天文学(英文版)》2011,(9)
Near-field acoustical holography (NAH) is a powerful tool for identifying noise sources and visualizing acoustic field. By recording the acoustic pressures in the near-field, the acoustic quantities in the whole 3-D field can be reconstructed and predicted. However, the current theory of NAH is not applicable to tracking large scale moving noise sources. Therefore, the hybrid near-field acoustical holography is developed for reconstructing acoustic radiation, which is derived from statistically optimized ne... 相似文献
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Planar nearfield acoustic holography (NAH) is extended to identify the sound source in a noisy environment. The extended method requires the knowledge of the pressures on two closely spaced parallel hologram planes and the plane wave reflection coefficient on the target source surface. First, the incoming field coming from the back side of the microphone array and the scattered field due to the incoming wave falling on the target source are correlated through the plane wave reflection coefficient on the target source surface. Then, the mixed field on the hologram plane can be represented by the field that would be radiated by the target source into free space and the incoming field. Finally, the field that would be radiated by the target source into free space can be extracted by using the pressures measured on two hologram planes, which will be further used to accurately identify the sound source via planar NAH. The validity of the proposed method is demonstrated by simulations and experiment, and the influence of the relative strength of the disturbing source to the target source is also investigated. 相似文献