共查询到20条相似文献,搜索用时 46 毫秒
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针对某些传递损失较大的消声器,现有白噪声测试设备的单一噪声源发生器无法满足消声量的测试需求。通过采用低频和中频两种声源发生器,利用过渡管道与测试管道垂直连接的方式,实现了两种声源组合发声对消声器声学性能的测试。为了解决过渡管道与组合声源系统连接处声阻抗变化,导致输出的噪声信号频谱特性随机波动的问题,提出了一种噪声信号的修正方法。该方法基于四传感器法测量过渡管道声阻抗,根据过渡管道传递矩阵,以随机白噪声为激励源输出的管口噪声作为输出声压信号,得到组合声源系统的输入声压信号,实现了对组合声源系统声音信号的补偿。实验结果表明,与传统均衡器调节方法相比,该方法能够在较宽的测试频率范围内输出平稳的声压信号;其次,利用修正前后的声学信号对扩张腔的传递损失进行测量,修正后得到的测试曲线与理论值吻合度较高,证明了该方法的可行性。 相似文献
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针对传统开关切换型噪声温度计存在测量时间长且需要匹配传输线的问题,搭建了一种量子电压标定的叠加型噪声温度计,从而消除切换开关。该方案一方面不需要匹配传输线,另一方面允许增加传感器电阻阻值从而提高测量的信噪比。系统主要包括量子电压赝噪声源、低噪声放大滤波电路和高精度数据采集电路等模块。采用四阶拟合外推到直流以消除传输线效应的影响,从而得到正确的热力学温度值。恒温实验室的验证性实验表明,经过100 s测量得到的结果与名义温度值的相对偏差为0.027%、不确定度为0.16%,说明了所提出方案的可行性。 相似文献
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差分吸收式光纤甲烷气体传感器的研究 总被引:1,自引:0,他引:1
设计一种新型的利用吸收法实现快速测量气体浓度的光纤传感器,该传感器基于比尔-朗伯定律,得到气体浓度与光强度变化的关系。利用差分吸收技术设计双光路双通道结构,消除了光源的不稳定性和光电器件的零漂。同时,设计了锁相放大器,抑制了噪声,从而提高了该传感器的灵敏度和测量精度。 相似文献
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分析了一种微波源调频噪声测量方法的原理,根据需要研制了一套微波源调频噪声测量系统,详细给出了为保证系统测量结果准确可靠所必需的调试步骤,并结合实际设计出一种独特的定标方法,使用该系统实测了一个22.68GHz锁相稳频信号的调频噪声,并对测量结果进行了讨论。 相似文献
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为控制某型号变流器噪声,文章对该变流器产品开展柜体内气动噪声仿真研究,并与试验结果对标,验证仿真方法可靠性,并协助进一步诊断噪声问题。仿真研究结果表明:机柜内部气动噪声源主要集中在风机附近区域,由风机叶片旋转引起的离散声源。风机噪声频谱在叶片通过频率及其他谐频出现明显峰值。文中对不同降噪方案进行仿真分析,对比了不同材料及不同厚度方案的降噪效果,并通过试验进行了验证。结果表明,使用吸声材料方案使出口总声压级降低 12.2 dB(A)。仿真分析法的降噪优化量与试验结果相近,该方法可应用于后续新产品的降噪设计。 相似文献
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S. G. BARNES 《Strain》1972,8(4):155-161
An important consideration in the measurement of high accuracy, low level, differential data signals is the effect of electrical interference or 'noise'.
The various techniques which can be used to minimise these effects, or reduce them, are considered. Typical sources of noise encountered in instrumentation systems are discussed and the additional problems associated with transmission systems are described. An analysis of the fundamental noise problem, capacitive coupling, is presented and an outline of the design principles which are necessary for accurate, noise–free measurements is given. 相似文献
The various techniques which can be used to minimise these effects, or reduce them, are considered. Typical sources of noise encountered in instrumentation systems are discussed and the additional problems associated with transmission systems are described. An analysis of the fundamental noise problem, capacitive coupling, is presented and an outline of the design principles which are necessary for accurate, noise–free measurements is given. 相似文献
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By comparing the analyses of magnetic recording media noise and shot noise, this paper shows that a very close analogy exists between the two. It demonstrates that all the well-known results for both kinds of noise are caused by random processes that have equal probabilities in equal volumes. 相似文献
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Valk E.C. Routledge D. Vaneldik J.F. Landecker T.L. 《IEEE transactions on instrumentation and measurement》1988,37(2):195-200
Equations are presented, suitable for computer or calculator, for accurately de-embedding the noise parameters of both the first and the second two-port in a cascade of noisy two-parts from known values of the noise parameters of the cascade. The derivations are presented in terms of a noise wave model for two-ports, using transfer scattering small signal parameters. A numerical example is presented in which the noise parameters of two cascaded passive two-ports having unequal physical temperatures are individually de-embedded from the noise parameters of the cascade. As a check on the analysis presented, the noise parameters of each two-port are also calculated directly from its scattering parameters and physical temperature 相似文献
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Cibiel G Régis M Tournier E Llopis O 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2002,49(6):784-788
The influence of the source AM noise in microwave residual phase noise experiments is investigated. The noise floor degradation problem, caused by the parasitic detection of this type of noise by an imperfectly balanced mixer, is solved thanks to a refinement of the quadrature condition. The parasitic noise contribution attributable to the AM to PM (phase modulation) conversion occurring in the device under test is minimized through the development of a dedicated microwave source featuring an AM noise level as low as -170 dBc/Hz at 10 kHz offset from a 3.5 GHz carrier 相似文献
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设置高架路声屏障降低城区交通噪声 总被引:3,自引:0,他引:3
针对城市交通噪声的声学特性 ,根据建筑声学原理 ,从噪声源控制、传播途径控制和接收者防护三个方面 ,阐述在高架路上设置隔声屏障的必要性及技术手段 ,并通过实例具体说明运算方法、设计要求和注意事项 相似文献
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A transformation to convert signal-dependent noise corrupting an image to additive Gaussian signal-independent noise is derived in this paper. Wiener filtering techniques using a Markovian covariance model for the image signal are applied to the transformed data followed by an inverse transformation to restore the degraded image. An ad hoc technique using contrast manipulation to adaptively convert signal-dependent noise to signal-independent noise is also described. The results of the computer simulations designed to evaluate the performance of these techniques are also presented. 相似文献
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《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2003,496(2-3):461-464
The performance of a high-resolution spectroscopy system is affected by the noise properties of the spectroscopy amplifier. A new approach for measurement of the noise at the output of the spectroscopy amplifier is presented. 相似文献