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1.
A method of implementing high cost-effective and highly integrated digital lock-in amplifier with microcontroller is discussed. And the digital lock-in amplifier is more suitable for measuring low-frequency weak signal.Digital signal sequence is obtained through sampling signal measured over an integer number of signal periods, but digital reference sequence is acquired through mathematical operation, then digital phase sensitive detection can be implemented by calculating the cross-correlation function of digital signal sequence and digital reference sequence.In addition, the frequency response and phase character of the digital lock-in amplifier is analyzed. Finally, the designed digital lock-in amplifier is achieved. Experimental results show that the digital lock-in amplifier can be used for measuring weak signal with low ignal-to-noise ratio. 相似文献
2.
可听阈内的切削声信号包含着丰富的刀具磨损信息。找出刀具磨损信息在可听阈内的主要集中频段能提高切削声信号的信噪比,改善识别结果。在提取了可听阈内切削声信号包含的刀具磨损信息的有效特征,建立了识别模型和对刀具磨损状态进行了级别划分的基础上,对不同频段切削声信号展开了识别实验。实验分析结果表明可听阈内刀具磨损信息主要集中在低频段。 相似文献
3.
穿透式空气耦合超声检测中,由于较低声波透射率、激励接收系统噪声及声波在介质中的散射噪声导致接收信号信噪比较低,小波阈值滤噪技术在解决上述问题时面临小波基、分解层数及阈值函数的选取难题。基于小波分析的基本原理,以单因素分析方法开展小波阈值滤噪试验研究。选择不同小波族(Daubechies,Symlet和Coiflet)中的小波基、小波分解层数(4~8层)及阈值函数(软阈值及改进阈值函数)对实际含噪超声信号进行小波阈值滤噪处理,并通过对比滤噪信号的信噪比及频谱特性得出不同参数对滤噪效果的影响。结果表明,选择Coiflet小波族中的小波基能获得具有更高信噪比及透射信号幅值的滤噪信号;分解层数越高,滤噪信号的信噪比越高,但增长趋势渐趋稳定;阈值函数对滤噪性能的影响并不十分显著,一般采用软阈值函数或改进阈值函数就能获得良好滤噪效果。 相似文献
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Hyun-Hoo Lee Sung-Jong Kim Sang-Kwon Lee 《Journal of Mechanical Science and Technology》2009,23(4):1182-1193
The gear whine sound of an axle system is one of the most important sound qualities in a sport utility vehicle (SUV). Previous
work has shown that, because of masking effects, it is difficult to evaluate the gear whine sound objectively by using only
the A-weighted sound pressure level. In this paper, a new objective evaluation method for this sound was developed by using
new sound metrics, which are developed based on the increment of signal to noise ration and the psychoacoustic parameters
in the paper, and the artificial neural network (ANN) used for the modeling of the correlation between objective and subjective
evaluation. This model developed by using ANN was applied to the objective evaluation of the axle-gear whine sound for real
SUVs and the output of the model was compared with subjective evaluation. The results indicate a good correlation of over
90 percent between the subjective and objective evaluations.
This paper was recommended for publication in revised form by Associate Editor Yeon June Kang
Professor Sang-Kwon Lee received a Ph.D. degree in ISVR (Institute of Sound and Vibration Research) from Southampton University in 1998. He joined
Hyundai Motor Research Center in Korea, working with the Automotive Noise and Vibration Control Group from 1985 to 1994. He
has been the Professor at the Department of Mechanical Engineering, Inha University, Inchon, Korea, since March 1999. His
research interests are the digital signal processing, NVH (noise vibration harahness), condition monitoring, product sound
quality design and active control. 相似文献
7.
低温电流比较仪是现代电测量技术中最为准确的比例量具,在传递量子化霍尔电阻基准的量值时发挥了独特的作用。为了进一步提高CCC的比例准确度,一个有效的方法是采用匝数较多的绕组。但国际上各实验室均遇到了绕组匝数较高时电流会发生跳跃的困难,目前未见到对此问题进行分析及提出解决办法的文章。本文对CCC系统的动态特性进行了分析,找到了产生该现象的原因,并采取措施改进了系统的动态特性,避免了跳跃现象。与国际上的同类装置相比,CCC的绕组匝数被提高了8倍,信噪比及比例准确度也有了很大的提高。结合其他措施,完成了综合不确定度为10^-10量级的量子化霍尔电阻标准装置。 相似文献
8.
相控震源对水平层状地下介质的高信噪比检测 总被引:4,自引:0,他引:4
为提高可控震源地震勘探数据的信噪比,采用能够产生定向地震波的相控震源,针对水平层状地下介质模型,给出了不同信噪比条件下的单震源、相控震源信号检测结果。使用单震源时不能分辨的目标层反射波信号,在相控震源地震记录中清晰可见;通过定量计算,用12单元的相控震源地震与单震源情况相比,反射波信噪比平均提高了19.25dB;与12单元的组合震源地震相比,反射波信噪比平均提高了8.46dB。可见,相控震源应用于水平层状地下目标体的高信噪比探测是可行的。 相似文献
9.
张少刚 《自动化与仪器仪表》2011,(6):147-148
本论文是探讨脉冲探测技术的,探讨了两个问题:要求实现信噪比的改善,最后形成高灵敏度的探测系统;在白噪声中探测宽度为τ的脉冲信号问题。 相似文献
10.
In this paper, the Artificial Bee Colony (ABC) algorithm is applied to construct Adaptive Noise Canceller (ANC) for electroencephalogram (EEG)/Event Related Potential (ERP) filtering with modified range selection, described as Bounded Range ABC (BR-ABC). ERP generated due to hand movement is filtered through Adaptive Noise Canceller (ANC) from the EEG signals. ANCs are also implemented with Least Mean Square (LMS) and Recursive Least Square (RLS) algorithm. Performance of the algorithms is evaluated in terms of Signal-to-Noise Ratio (SNR) in dB, correlation between resultant and template ERP, and mean value difference. Testing of their noise attenuation capability is done on contaminated ERP with white noise at different SNR levels. A comparative study of the performance of conventional gradient based methods like LMS, RLS, and ABC algorithm is also made which reveals that ABC algorithm gives better performance in highly noisy environment. 相似文献