消声

The finite element method is applied to analyze the attenuation performance, which is basing on that porous clapboard, porous pipes and absorbent are accurately modeled and the influence of temperature, velocity and tail reflection is taken into account.

采用有限元方法，在对穿孔隔板、穿孔管和吸声材料进行精确建模，并考虑温度、流速和尾管反射对消声的影响的基础上，对消声特性进行分析。

Based on a series of signal process and noise source identification techniques, especially the major noise source identification methods, such as expurgation method, sound intensity analysis, spectrum analysis vibro-acoustic correlation analysis and so on, the pass-by noise control of SC7080A and SC6360B are studied in detail. By the roadway and dais experiments, the major noise and radiating parts are identified and some economical controlling methods are made. For the SC7080A, to control the emissing noise from the intake and shell vibration of air cleaner, a intake muffler is installed between the air cleaner and intake valve. Based on the theory of Helmholtz resonator, One three-parallel-connected resonant silencer is designed and trial-manufactured. For the SC6360B, the attenuation performance of exhaust muffler in high frequency region is improved. To reduce the vibration noise of shell part, the structure of oil sump tank, exhaust manifold shield and exhaust manifold shield are analyzed and improved. At the same time, some measures, such as sound absorption, sound insulation, are taken to reduce the noise of engine surface emissivity and a sound shield is designed.

本文首先综述了目前国内外汽车加速噪声控制的现状、主要方法和技术措施，在此基础上，结合SC7080A和SC6350B汽车的车外加速噪声水平及现状，综合运用分别运行法、声强法、频谱分析法、声振相干函数法等现代噪声源识别方法，对SC7080A和SC6360B汽车进行了准确详细的车外加速噪声源识别并提出了经济可行的控制方案，针对SC7080A，主要在空气滤清器和进气阀门之间的进气管道上加装进气消声器，抑制空气滤清器壳体表面和进气口两处的噪声辐射，根据Helmholtz共振腔原理设计了三腔并联旁支型共振消声器，并进行了工程化设计和试制；针对SC6360B，主要改善了排气消声器在高频段的消声性能，对罩壳类零件进行了结构改进，降低了其表面噪声的辐射，并对发动机舱进行了吸声、隔声处理，设计了发动机隔声罩。

Based on Huygens' principle, the basic equations in the ideal medium and the theory of field diffraction, the paper gives theoretical studies of ANC in space, including the mechanism of attenuation of noise, basic characteristics of radiation and the way of energy transfer.

本文从Huygens原理、理想媒质中的基本方程和场衍射理论出发，对空间有源消声的基本理论进行了探讨，分析了次级声源的消声原理、基本辐射特性和能量转换，提出了空间有源消声所减小的声能主要通过次级声源和初级声源本身转换成其它形式的能量的思想，并在实验上进行了验证。

In this paper, based on Maa's theory, the theory of micro perforated panel absorber is summarized, a comparison between the calculated result and the testing result for intermediate and lower frequency standing wave tubes is made.

在微穿孔板消声理论的基础上，根据气动马达消声器的实际需要设计了一种微穿孔板消声器，并通过实验对这种消声器的消声特性和流阻进行了研究。

Based on the repeated tests, the optimum structure of muffler were defined and the influence of inside pipe structure variation of the muffler on muffling effect were studied.

在大量试验的基础上，研究了二级扩张室式消声器中穿孔管结构的变化对消声器消声效果的影响，并优选出最佳结构的消声器，该消声器消声量大且功率损失小，能满足对内燃机日益严格的噪声要求

Active noise control is achieved by introducing a canceling "anti-noise"wave of equal amplitude and opposite phase using a secondary source.

主动消声是利用声波之间的相消性干涉原理，使声场局部区域声能相互抵消，从而达到降低噪声的目的。

Our products cover anechoic chamber, acoustic test facilities, sound enclosure, recording room, audiometric room, acoustic door and acoustic panels.

产品涵盖消声室、隔声室等声学测试设施、录音室、测听室等专业用房、隔声罩、声屏障等降噪装置、以及隔声门、隔声板、吸声板、消声器等专业产品。

Finally, a bi_layer coating (with a thickness of 20mm) is designed for broad_band anechoic material.

最后，设计了双层消声覆盖层(厚度为20mm)，有效拓展了消声带宽。

Referring to regular cuboids, two different performance functions are presented for irregular enclosures in this paper. The optimum voltages applied on PZT patches for active noise control are obtained by minimizing two performance functions.

参考长方体封闭空间的情况，本文在不规则封闭空间的有源消声中提出了两种控制目标函数，通过使控制目标函数最小化得到了有源消声控制电压的最优值。

Using fluid dynamics FEM (two dimensional, three dimensional andaxisymmetric) and three dimensional acoustic FEM in meticulous analysis ofexpansion muffler structure, this paper studies the influences of each mufflercomponents' position, dimension, form and quantity on the fluid dynamic andacoustic performances;therefore the paper indicates that the end of the intruding tubeis the linchpin of the fluid dynamic performance of the whole muffler structure, thespringhead of muffler fluid dynamic performance is the smoothness of air current, themain factor which affects the acoustic attenuation value of expansion chamber muffleris the grade of saltation of the section of air conducting access, and the attenuationvalue of specific frequency can be dramatically enhanced by carefully designing thelength of expansion chamber.

本文通过流体力学有限元方法和三维声学有限元方法对扩张腔消声结构的参数化模型进行了细致的分析，研究了这种结构的各个组成部份的位置、大小、形状和数量对其流体力学与声学性能的影响，指出插入管端口是影响整个结构流体力学性能的关键，消声结构流体力学性能的根源是气流通过时的平稳程度；影响扩张腔消声量的主要因素为声波传播通路截面突变的程度，并可以通过精细的设计扩张腔轴向长度获得宽频或指定频率消声量的大幅度提高。

Finally, according to market conditions and market products this article paper analyzes the trends in the development of camera technology, and designs a color night vision camera.

最后根据市场情况和市面上产品的情况分析了摄像机技术的发展趋势，并设计了一款彩色夜视摄像机。

Only person height weeds and the fierce looks stone idles were there.

只有半人深的荒草和龇牙咧嘴的神像。