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1.
数字化是当今世界上声学测量技术的发展趋势,它采用微计算机和数字信号处理系统.数字化声学测量的主要优点是:1.精确度高,动态范围大2.性能稳定,可靠3.可实现许多模拟仪器设备不能完成的复杂功能4.使用灵活方便5.优异的性能价格比.本文综合介绍了数字化声学测量技术的这些优越性,同时还介绍了一种实际使用的数字化声学测量系统的组成和工作原理,以及它的主要测量分析功能.本文可为涉及声学测量的部门和单位在选择仪器设备时提供参考. 相似文献
2.
本文介绍在数字声学测量分析系统中,通过双传声器信号互谱密度的计算进行声强及声功率测量的基本原理。该数学分析系统由微计算机,数字信号处理卡和A/D变换卡组成。在一个数字系统中,通过快速傅里叶变换(FET)进行互谱计算是十分有效的。本文着重介绍了,在声强的测量分析中对声强探头两传声器的固有相位差进行补偿的重要性和补偿方法,这是声强测量的重要环节。 相似文献
3.
消声室声学技术的革新 总被引:1,自引:0,他引:1
半个多世纪以来,在室内建立自由声场,以尖劈为基本吸声构造,尖劈的长度基本定于所需的低频截止频率,建造尖劈占用大量体积的事实,似乎都是无需讨论或必须接受的。随着科学技术的发展,尖劈的长度要求(1/4波长),已经成为自由场室扩展低频截止频率的实际障碍。工业技术发展需要的自由场室,不仅有它特殊需要的低频下限,例如到50Hz,决定于它的环境条件,对于吸声构造又有相应的使用和维护方面的要求。本文从室内稳态声场的理论分析出发,提出扩展低频截止频率,以阻尼房间的简正振动为基本,界面的反射,应从在室内更接近球面声波的实际出发,建立自由声场的新思想。介绍了新开发的三种新型无纤维吸声构件和适应不同要求的两类自由场室。以一间已经建设成功的半自由场室为例,用复合板共振吸声器(CPA)和非对称构造吸声器(ASA)组合,吸声构件的厚度仅620cm,得到的自由场结果是:以1/3倍频程频带信号测试(这正是该室的使用测试信号),25Hz至80Hz,±2.5dB,100~16000Hz,±1.0dB,自由场范围9m至12m。以正弦信号测试,100Hz以上达到和频带噪声类似结果,100Hz以下至50Hz,自由场范围7m至9m。已建成50间以上类似的自由场室。 相似文献
4.
扬声器的主要特性是灵敏度频率响应,习惯上指幅度频率特性。通常是在消声室内用正弦信号扫描方法测量。扬声器的测量技术从50年代以来进展缓慢。考虑到语言和音乐本质上是一种瞬态信号,因此一度建议使用猝发声、阶梯波和脉冲来测量扬声器的响应。但是在使用模拟式测量设备时,脉冲的能量很小,使信噪比很低,数据分析也有困难,使它们无法实用。最近,数字计算机的应用,快速傅里叶变换的出现,使一种测量扬声器脉冲响应再计算其转移函数的新方法获得了实际应用。它不但用于扬声器的设计和研制,也已应用于生产中。 相似文献
5.
设扬声器是线性定常系统。它的系统函数H(ω)可以用振幅特性A(ω)和相位特性φ(ω)或群时延特性τ(ω)来表示: H(ω)=A(ω)·exp[jφ(ω)] 相似文献
6.
厅堂声学测量中不同激励声源的比较 总被引:3,自引:0,他引:3
基於脉冲响应积分的音乐厅和剧院观众厅声学特性的测量目前有三种使用不同激励声源的测试方法:人工脉冲声源、伪随机噪声序列(MLS)、以及用正弦扫频信号。这些技术各有其优缺点,在实际应用中为了方便根据具体情况选择不同的激励声源,通过在一个音乐厅现场的实测数据比较丁三种声源的实测结果,发现对混响时间测量三种不同的激励声源给出的结果基本一致,但是对明晰度和一些其他的指标,脉冲声源给出的结果与用MLS和扫频信号给出的结果有较明显的差别。对实际中如何选择具体的技术也做了建议。 相似文献
7.
Anechoic chambers are used for indoor antenna measurements. The common method of constructing an anechoic chamber is to cover all inside walls by the electromagnetic absorbers. In this paper, a fully metallic spherical chamber structure is presented in which the propagation of the electromagnetic waves inside the chamber is controlled and they are guided to an absorber. In the proposed method, an appropriate quiet zone is obtained, and unlike ordinary anechoic chambers, the absorber usage amount is reduced greatly. The performance of the chamber is evaluated by simulation. The results show that the proposed method could provide a useful technique for the indoor antenna measurements. 相似文献
8.
风洞试验是进行民用飞机机体噪声研究的重要手段。为了满足航空飞行器低噪声设计在大型风洞中进行气动噪声试验的需求,中国航空工业空气动力研究院建设了FL-10大型低速风洞全消声室。通过在FL-10风洞试验大厅壁面安装吸声尖劈、对洞体外表面进行声学处理、对支撑系统进行隔声处理、对消声换气窗进行降噪处理等手段,建成了气动噪声风洞试验所需的声学环境。按照国家标准中给定的方法,利用张线方法实现了校准声源的布置,测量了消声室内沿不同路径、不同频率噪声的衰减规律,表明FL-10风洞消声室自由场特性达到了相应标准的要求,为后续在该风洞中进行大尺寸机体模型噪声试验奠定了基础。 相似文献
9.
O. Braz G. Dammertz M. Kuntze M. Thumm 《International Journal of Infrared and Millimeter Waves》1997,18(8):1465-1477
In order to demonstrate the usability of gyrotron oscillators as frequency step tunable high power millimeter-wave sources,
experiments on a 1 MW, 140 GHz TE22,6 gyrotron with a built-in quasi-optical (q. o.) mode converter have been performed. By varying the operating parameters of
the tube, a series of oscillations in the frequency range from 114 GHz to 166 GHz were excited. To avoid reflections, caused
by the required vacuum barrier window, the gyrotron was equipped with a Brewster window. The achieved output power levels
between 0.85 and 1.05 MW are compared to measurements carried out with the same tube using a conventional single-disk window.
These experiments showed that even by using a q. o. mode converter, the influence of window reflections on the gyrotron oscillatory
behavior cannot be removed completely. 相似文献
10.
In the paper an important issue of vibrations of the transmission line in real conditions was analyzed. Such research was carried out by the authors of this paper taking into account the cross-section of the cable being in use on thetransmission line. Analysis was performed for the modern ACSR high voltage transmission line with span of 213.0 m. The purpose of the investigation was to analyze the vibrations of the power transmission line in the natural environmentand compare with the results obtained in the numerical simulations. Analysis was performed for natural and wind excited vibrations. The numerical model was made using the Spectral Element Method. In the spectral model, for variousparameters of stiffness, damping and tension force, the system response was checked and compared with the results of the accelerations obtained in the situ measurements. A frequency response functions (FRF) were calculated. Thecredibility of the model was assessed through a validation process carried out by comparing graphical plots of FRF functions and numerical values expressing differences in acceleration amplitude (MSG), phase angle differences (PSG) and differences in acceleration and phase angle total (CSG) values. Particular attention was paid to the hysteretic damping analysis. Sensitivity of the wave number was performed for changing of the tension force and section area of thecable. The next aspect constituting the purpose of this paper was to present the wide possibilities of modelling and simulation of slender conductors using the Spectral Element Method. The obtained results show very good accuracy in the range of both experimental measurements as well as simulation analysis. The paper emphasizes the ease with which the sensitivity of the conductor and its response to changes in density of spectral mesh division, cable cross-section,tensile strength or material damping can be studied. 相似文献
11.
针对现有准函数脉冲压力校准法存在的缺点,提出了一种预先给压力传感器施加高静压,再利用子弹撞击霍普金森杆产生幅值较小的准信号激励传感器,获得压力传感器频响特性的动态校准方法。阐述了准函数脉冲压力校准原理,分析了准信号的脉宽与频率校准范围、校准精度三者之间的关系,建立了动态校准系统该校准方法实现了在实际工作压力下校准压力传感器,可校准的下限频率严格地达到零频。就目前的校准技术而言,对传感器施加的最大静压是800 MPa,产生的准信号的脉宽为7~10 s,可校准的频率范围为0~20 kHz,幅频特性校准误差为5%。 相似文献
12.
Computational analyses of the effects of oxidiser injector length on combustion instability in a choked high pressure combustor are described. The configuration is based on companion experiments using gaseous methane and decomposed hydrogen peroxide as reactants. The generic behaviour of one injector length is first investigated in detail to investigate the general character of the flow-fields. Comparisons between computation and experiment are then given for five lengths. The predictions for the intermediate lengths are in good agreement with the experiments in terms of most unstable frequency, its amplitude and the rate of decay of higher harmonics. The computations for the shortest injector predict the second mode is most unstable whereas the experiment indicates the fundamental was more unstable. At the longest length the computations show a character similar to the other lengths, while the experiments indicate the instability jumps to much higher frequencies that did not appear in the computations. A series of post-processing diagnostics is used to assess the mechanisms causing instability and to give possible explanations for the experimental behaviour. 相似文献
13.
土壤-地雷共振系统模型解析 总被引:3,自引:0,他引:3
在研究土壤-地雷共振系统模型的基础上,提出一种共振与反共振相结合的声波探雷模型.根据地雷顺性大及低频声学的特征,把地雷与其上方的土壤分别等效为弹簧和质量块,构成质量-弹簧共振系统,通过对系统频响函数的解析,讨论模型的共振与反共振现象.通过实验发现有、无地雷的地表振动速度比值存在大于1的极大值频率点和小于1的极小值频率点交替出现的现象,与理论预测符合.表明土壤-地雷共振系统同时存在共振与反共振现象,可用于地雷成像的研究.关键词:共振模型反共振频响函数声波探雷 相似文献
14.
15.
光谱色散匀滑对焦斑光强频谱的影响 总被引:2,自引:0,他引:2
基于焦斑光强的空间频谱分析方法,建立了光谱色散匀滑技术(SSD)对焦斑匀滑的影响模型,提出了控制焦斑空间频率调制的响应函数.揭示了SSD参量对空间频率响应函数的影响规律.理论推导和数值模拟结果都表明:SSD对焦斑光强的频率响应具有周期调制性质,调制特性和色散角、光谱形状等相关.一般地,光谱形状控制空间响应函数形状,色散角决定所能匀滑的最低频率,色循环数可改变响应函数特点,调整对空间低频和高频的匀滑效果.空间频率响应函数的特点为多维SSD应用提出了应用准则.关键词:光谱色散匀滑空间频谱焦斑响应函数 相似文献