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车内的低频噪声影响汽车的乘坐舒适性。为此以人工头双耳记录的车内噪声信号为研究对象,通过主观评价试验,并对结果进行分析。提取了影响车内噪声低沉度的特征参量,建立了以1/3倍频程声压级、锐度和粗糙度为变量的低沉度参量特征模型。采用两种不同的主观评价,结果表明,低沉度模型的预测结果与主观评价结果具有很高的相关性。 相似文献
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基于小波包的振动信号去噪应用与研究 总被引:6,自引:1,他引:6
小波包分析算法对上一层的低频部分和高频部分同时进行细分,具有更为精确的局部分析能力。基于小波包变换的优良时频分析特性,论述小波包分析的基本原理,研究小波包在振动检测信号消噪处理中的应用,给出应用小波包变换对基于MSP430F449单片机的信号采集电路所检测到的振动信号进行消噪处理的实例。结果表明小波包变换的方法可以降低系统噪声影响,通过变换分解出高频噪声部分,利用小波包收缩的阈值量化方法能够更好地去掉高频部分,从而达到有效去除信号中噪声的目的。 相似文献
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针对传统心音去噪算法对强噪声下心音信号去噪时,易将部分心音信号视为噪声成分去除,导致有用心音信号能量损失。利用奇异谱分析方法的主成分分析特性,提出多级奇异值分解(Multi-stage Singular Value Decomposition,MS-SVD)算法用于提取心音信号的主分量(Principal Components,PC)信息;采用小波包(Wavelet Packet,WP)分析算法对提取的心音信号进行分解,并对分解所得低频系数进行自适应阈值处理,去除低频噪声;利用小波包多分辨率特性提取高频心音。实验结果表明,该算法能明显改善心音去噪性能指标信噪比(SNR)、信噪比增益(SNRG)及根均方误差(RMSE),且在不同噪声水平下的去噪性能优于传统心音去噪算法。此改进算法既能有效去除心音中噪声成分,亦能保留心音信号细节特征。 相似文献
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在列车经过钢弹簧浮置板地段时,车内产生中低频噪声,影响着人们乘车环境舒适性。通过对不同钢弹簧浮置板轨道地段车内噪声的对比测试,分析钢弹簧浮置板轨道对车内噪声的影响,结果表明采用高阻尼钢弹簧浮置板轨道可有效降低车内噪声。 相似文献
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本文主要介绍了旋转式压缩机储液器的噪声特点及对总体噪声的贡献,并在此基础上对其结构进行了相应改进,从而有效地降低了压缩机的总体噪声。 相似文献
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为研究在飞机噪声监测中背景噪声客观上无法满足标准要求时的数据有效性问题,选择在低噪声环境,距机场不同距离的位置测得基本不受背景噪声影响的飞机噪声数据,在上述数据的基础上叠加模拟的背景噪声,以分析背景噪声对监测结果的影响,分析表明:随着背景噪声的增加,飞机可感觉噪声级随着之增大;且背景噪声越高,增幅越大;当飞机最大等声级大于背景噪声15 dB以上时,增幅趋于稳定。进一步分析表明:造成可感觉噪声级变大的原因主要是飞机持续时间变长。基于上述结论,在监测中,若飞机最大声级与背景噪声的差值大于15 dB时,监测结果仍可较真实的反映测点受飞机噪声的影响情况;若小于15 dB,则监测结果与不受背景噪声影响时相比,偏大较多。当飞机最大声级仅高于背景噪声10 dB时:对于特大型机场,监测点位于1~2 声环境达标类区时,其飞机噪声达标判定会受
到干扰;对于大型机场,监测点位于2 类声环境达标区时,其飞机噪声达标判定会受到干扰;而对于中型机场,则其达标判定基本不受干扰。当飞机最大声级高于背景噪声15 dB时,其达标判定也基本不受干扰。 相似文献
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I. A. Chaban 《Journal of Superconductivity》1999,12(5):601-607
The mechanism capable to explain the peculiarities of both the telegraph noise and flicker noise in high-temperature superconductors (HTS)—in particular, their common behavior—is proposed. It bases on the impurity mechanism of high-temperature superconductivity and the suggestion that an origin of the flicker noise in most cases is a process that can be described by the equation of diffusion type, with a medium discreteness taken into account. In the transition region, the flicker noise and telegraph noise are explained by fluctuations of the concentration (x
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) of the two-level systems each having a localized electron pair. These fluctuations disappear according to the diffusion equation. The telegraph noise is considered as a result of opening and closing superconducting and nonsuperconducting channels due to the x
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fluctuations. In the normal state, the flicker noise is explained by concentration fluctuations of different impurities that change the charge carrier mobility. 相似文献
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Carolyn L. Kane 《History of Photography》2016,40(2):129-145
Like past avant-garde movements, glitch and noise in the twenty-first century are used to reveal the materiality of the medium. But instead of providing insight or clarity into the politics or social conditions of a technology, they demarcate broader conditions of opacity and blockage, contributing to what Jodi Dean has called ‘communicative capitalism’. The work of German photographer Thomas Ruff alongside the Düsseldorf School, New Photography and JPEG technology are used in this article to illustrate this tendency as a move away from meaning and toward visual noise and communicative breakdown. I use three core analytic registers: the deliberate failure to adhere to visual norms, communicative failure and machine failure and breakdown. Ruff’s work uses visual noise as art to at once reaffirm pervasive conditions of breakdown, failure and decline in high-tech global capitalism, while simultaneously providing a temporary reprieve from these conditions through an emergent form of visual beauty. 相似文献
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《IEEE transactions on instrumentation and measurement》1984,33(4):263-268
A measurement system is described which allows us to determine the noise temperature of mismatched noise sources with unknown reflection coefficients. The system consists of a null-balancing radiometer extended by a circuit to compensate for the reduced noise power emitted by the mismatched one-port. In this circuit, no passive nonreciprocal components are necessary. Special consideration is given to measurement errors that are caused by the correlation of the input and output noise waves of the radiometer preamplifiers. Several methods to eliminate these errors are described. Furthermore, a circuit is given by which the measurement range is extended down to 0 K without the use of cold reference noise sources. Finally, a practical setup, operating in the 20-40-MHz range, is described together with corresponding measurement results. 相似文献
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Chih-Hung Chen Ying-Lien Wang Bakr M.H. Zheng Zeng 《IEEE transactions on instrumentation and measurement》2008,57(11):2462-2471
A novel method to determine the noise parameters of receivers or devices under test (DUTs) for on-wafer microwave noise measurements is presented. An iterative technique is utilized, and fast convergence is achieved by the proposed impedance selection principle. This proposed method reduces the parameter variations in the conventional methods. The impact of the impedance difference on noise parameter determination is experimentally evaluated using a DUT fabricated in a standard 90-nm CMOS technology. 相似文献
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在几乎所有的图像处理领域,在正式对图像处理之前,为了改善图像的质量,一般都要去除在图像传输等过程中产生的噪声。笔者介绍了一种新的去噪方法,该方法是基于噪声的概念提出的,对去除诸如椒盐噪声、随机噪声等效果都很好,尤其对随机噪声更显出其优势。该算法简单有效,容易实现。最后给出了在不同噪声量的情况下试验的对比图,经过大量的试验证明,这种新的算法能得到很好的去噪效果。 相似文献
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对纺织厂织布车间,细纱车间的噪声情况做了调研与测试。分析纺织厂的噪声现状。整群抽样选取对比组,通过问卷调查和实地测试相结合方法,探讨噪声对生产和工人身心健康的影响,提出降噪综合控制方法,并通过实验测试得以验证。 相似文献