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1.
陈端石 《应用声学》1989,8(2):17-21
本文介绍为了对柴油机本身做降噪改进设计而在实验室进行的噪声源识别实验研究。采用铅包覆法和国际上近年来发展的声强法两种方法。在铅包覆法实验中柴油机全部包覆后整机噪声级下降13.8dB(A)。声强法中应用一般的双通道FFT分析仪和通用微机,经接口组成测量分析系统。两种方法所得结果基本相符,而声强法的特点是简便易行,更利于在研究开发和工程中推广应用。  相似文献   

2.
光纤陀螺的噪声及其实验分析   总被引:1,自引:0,他引:1  
龚智炳  郭栓运 《应用光学》1991,12(5):46-49,42
通过对FOG-110-I全光纤陀螺仪样机的研制,分析了光纤陀螺的噪声源,并对信号光背向反馈进入激光器引起的强度噪声和由光纤PZT位相调制器引起的幅度调制对光纤陀螺系统的影响作了重点分析。最后,给出了FOG-110-I全光纤陀螺样机的测试结果和实验分析。  相似文献   

3.
间歇性排气噪声源的特性及消声器结构的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
排气噪声可分为稳定排气噪声,周期性排气噪声和间歇性排气噪声,通过对锻压机离合器与制动器的排气噪声源的特性研究,指出间歇性气噪声是由管道噪声,阀门噪声和喷口噪声所组成,首次指出了间歇性排气噪声存在单极子噪声及爆炸声。通过理论计算及试验建立了一种有效的滤波了噪消声器结构。  相似文献   

4.
声强测量作为新的测试手段在噪声控制领域中应用愈来愈广。为了提高实验效率,扩大应用范围,本文实现了声强测量的计算机控制。编制了测算声功率及测绘声强三维分布图的应用软件。在此基础上,通过实验说明了声强测量在测量声功率及鉴别噪声源方面的应用及其优点。  相似文献   

5.
金磊 《工科物理》1999,9(1):29-32
声环境是环绕人们的并对其生存产生很大影响的重要条件,但以往人类只注意发展声环境的正向方面,而对于由此产生的隐伏的声危害却关注不够,从而致命声环境会给人类带来灾难性的环境压力,主人类健康,本文重点介绍突出的灾害噪声问题及其控制技术。  相似文献   

6.
选择声强法用于强背景噪声下声源识别   总被引:3,自引:0,他引:3       下载免费PDF全文
选择声强法是一种新的测试方法,它集中了传统声强法和偏相干方法的优点,可以在声源间存在相干和高背景噪声的情况下,进行声源辐射声强的识别.本文首先论述了选择声强法的理论,并在多输入、双输出的频域模型基础上,讨论了如何利用选择声强法将声强矢量分解为与各噪声源有关的分量,然后结合在强背景噪声下扬声器辐射声强的区分实验,给出了此方法在实际应用中可能遇到的一些问题以及相应的解决办法.  相似文献   

7.
声环境是环绕人们的并对其生存产生很大影响的重要条件,但以往人类只注意发展声环境的正向方面,而对于由此产生的隐伏的声危害却关注不够,从而致使声环境会给人类带来灾难性的环境压力,危及人类健康.本文重点介绍突出的灾害噪声问题及其控制技术.  相似文献   

8.
考虑加速度的交通噪声源强研究   总被引:3,自引:1,他引:2       下载免费PDF全文
林郁山  蔡铭  李锋 《应用声学》2012,31(4):282-286
本文为研究机动车噪声源强与速度、加速度的关系,对车辆在不同速度和加速度下的A计权声压级进行测试,运用统计学方法对测试数据进行分析,得到机动车单车噪声源强与车辆速度、加速度的关系模型,并与《公路建设项目环境影响评价规范(JTG B03-2006)》中的交通噪声源强预测模型进行比较,实测验证结果表明,利用本研究建立的机动车单车噪声源强模型所得预测结果更符合实际。  相似文献   

9.
王怀应 《应用声学》1998,17(3):15-19
本文介绍了强测量技术在水下结构辐射近场测量中的实际测量系统,特别是水下声系统的扫描平面的实现方法及定位误差控制方法,最后讨论和分析了实际测量结果,从而说明该系统用水下声强测量是可行的。  相似文献   

10.
江鹏飞  林建恒  孙军平  衣雪娟 《物理学报》2017,66(1):14306-014306
考虑到海洋环境噪声源深度分布不集中,建立了噪声源随深度分布的海洋环境噪声模型,分析了源深度对噪声场垂向特征的影响并从简正波角度予以解释,发现海底声阻抗和声源深度都显著影响由海洋环境噪声获得的等效海底反射损失大掠射角部分,进而将该模型用于地声参数反演.两段实测噪声数据200—525 Hz频段的反演结果表明:基于海洋环境噪声的地声参数反演最优值与声传播的反演结果相近;源平均深度最优值随频率增加有变小的趋势,说明随频率增加环境噪声主要贡献源逐渐由航船转为风浪;当海况大于3级时,400 Hz以上频段噪声源深度平均值很小,与Monahan气泡理论的描述一致.  相似文献   

11.
Hybrid near-field acoustical holography(NAH) is developed for reconstructing acoustic radiation from a cylindrical source in a complex underwater environment. In hybrid NAH,we combine statistically optimized near-field acoustical holography(SONAH) and broadband acoustical holography from intensity measurements(BAHIM) to reconstruct the underwater cylindrical source field. First,the BAHIM is utilized to regenerate as much acoustic pressures on the hologram surface as necessary,and then the acoustic pressures are taken as input to the formulation implemented numerically by SONAH. The main advantages of this technology are that the complex pressure on the hologram surface can be reconstructed without reference signal,and the measurement array can be smaller than the source,thus the practicability and efficiency of this technology are greatly enhanced. Numerical examples of a cylindrical source are demonstrated. Test results show that hybrid NAH can yield a more accurate reconstruction than conventional NAH. Then,an experiment has been carried out with a vector hydrophone array. The experimental results show the advantage of hybrid NAH in the reconstruction of an acoustic field and the feasibility of using a vector hydrophone array in an underwater NAH measurement,as well as the identification and localization of noise sources.  相似文献   

12.
平面近场声全息中正则化参数的确定   总被引:2,自引:0,他引:2  
近场声全息的逆向重建过程属于线性病态逆问题,必须进行正则化处理。本文对三种基于Tikhonov正则化的参数选择方法,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,它们在远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,对其中较为稳定的离差原理进行了改进,使其在较远全息距离及低噪声环境下仍能获得合适的正则化参数。相应的仿真实验表明,改进后的离差原理法在很宽的信噪比(6 dB)和较远的全息距离(~10 cm)均能稳定地找到合适的正则化参数。此外,由于该方法无须对全息声压进行平滑处理,其有效重建孔径和全息孔径相等。  相似文献   

13.
Cyclostationary sound field is a special kind of nonstationary sound field, in which the pressure signal is modulated seriously and sidebands exist in its spectrum. The reconstructed sound field can't figure the cyclostationary features in conventional Nearfield Acoustic Holography (NAH) procedure. On the basis of planar cyclostationary NAH, the cyclostationary NAH based on boundary element method is proposed which can be utilized to analyze radiators with complicated surface. Replacing the Fourier's transform with the second-order cyclic statistics, the Cyclic Spectral Density (CSD) functions is used as the reconstructed physical quantity in the proposed NAH technique, instead of the spectrum or power spectral density of pressure signal. By virtue of the demodulation ability of CSD function, the reconstructed CSD can effectively express the information of modulating and carrier wave respectively. The simulation and experiment illustrate that the validity and accuracy of this cyclostationary NAH technique satisfy the request of engineering.  相似文献   

14.
The current main approach to reconstruct and predict the acoustic field of a planar source is Near-field Acoustical Holography (NAH) based on FFT. But this method has some disadvantages such as wraparound error and edge Gibbs phenomena which will contaminate the results badly. A planar NAH based on equivalent source approach is developed, which has no wraparound error and edge Gibbs phenomena, and it is beneficial for engineering application. The experimental results of acoustic radiation generated by a point-driven plate with clamped boundaries validate the correctness and availability of the method.  相似文献   

15.
This article presents the implementation and application, to two complex machines, of two holography methods called CIBNAH (Complex Intensity Based Near-field Acoustic Holography) and MRNAH (Multi Reference Near-field Acoustic Holography) based on residual spectra. The first is a newly developed method that uses complex sound intensity as its basis and hence bypasses the need for reference signals. Here, several approaches are presented to validate both methods and to investigate each method’s advantages and limitations.  相似文献   

16.
This paper reviews the theoretical analysis of the imaging method andcharacteristic of the Nearfield Acoustical Holography(NAH).We present anew filtering method,least squares method for filtering with restraint,whichimproves the stability of the reconstruction.The computer simulation experi-ment for the vibration and radiation of a round plate by means of the numericalmethod of NAH has been done and the effect of the new filtering method hasbeen verified.The NAH imaging of radiation of a small loudspeaker using ascanning linear receiving array of 32 elements has been made and the prelimina-ry results are given in the paper.  相似文献   

17.
Statistically optimized near field acoustic holography (SONAH) differs from conventional near field acoustic holography (NAH) by avoiding spatial Fourier transforms; the processing is done directly in the spatial domain. The main advantage of SONAH compared with NAH is that the usual requirement of a measurement aperture that extends well beyond the source can be relaxed. Both NAH and SONAH are based on the assumption that all sources are on one side of the measurement plane whereas the other side is source free. An extension of the SONAH procedure based on measurement with a double layer array of pressure microphones has been suggested. The double layer technique makes it possible to distinguish between sources on the two sides of the array and thus suppress the influence of extraneous noise coming from the "wrong" side. It has also recently been demonstrated that there are significant advantages in NAH based on an array of acoustic particle velocity transducers (in a single layer) compared with NAH based on an array of pressure microphones. This investigation combines the two ideas and examines SONAH based on an array of pressure-velocity intensity probes through computer simulations as well as experimentally.  相似文献   

18.
This paper describes a detailed implementation and application of the intensity-based holography method called BAHIM, and it investigates its possibilities and its limitations. Although this method is attractive in the sense that it bypasses the reference signal requirement, i.e., one of the main difficulties of the classical near-field acoustic holography, its degree of accuracy does not appear to be adequate. This constraint has consequently led to the development of another method called CIBNAH, based on complex intensity, as an alternative. This novel approach provides additional accuracy in detecting and localizing sources and good compatibility, in form and amplitude, with NAH results.  相似文献   

19.
Conventional near-field acoustical holography (NAH) is generally based on the free-field assumption, which can cause errors when interfering sources are present in practical environments. To cope with this problem, previous research suggested a combined pressure-velocity approach for NAH that provides certain advantages to rejection of interferences. This paper revisits this idea in a broader context of optimal array design and examines the feasibility of using unidirectional microphones in each channel of the array such that the robustness of inverse reconstruction is enhanced against interfering sources. As indicated in the simulation, the numerical noise in finite difference estimation of particle velocity can nullify the advantage of the well-conditioned velocity-based reconstruction. In the proposed approach, the characteristics of each array channel consisting of two microphones are tailored by taking into account not only the directivity, but also the robustness against self-noise. An objective function based on directivity index and white noise gain is exploited in a linear quadratic optimization of a two-element end-fire array. The proposed optimal array is validated in conjunction with the equivalent source model (ESM) -based NAH through numerical simulations, with an interfering source positioned behind the array. The results have shown the directive optimal array has yielded improved quality of images in comparison with conventional approaches in the presence of an interfering source and sensor noise.  相似文献   

20.
The regularization method for measurement of structural intensity (SI) using boundary element method (BEM)-based nearfield acoustical holography (NAH) is proposed. Spatial derivatives of normal displacement are necessary to obtain the structural intensity. The derivative operations amplify high-wavenumber component of measurement noise and contaminate the measurement result of SI. To overcome this difficulty, regularization method for measurement of SI using fast Fourier transform-based NAH has been introduced. In this paper, this regularization method is modified for the BEM-based NAH. The BEM-based NAH avoids the aperture replication problem; therefore, measurement aperture for BEM-based NAH can be set smaller than that for FFT-based NAH. The effectiveness of the proposed method is demonstrated by experiments.  相似文献   

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