共查询到20条相似文献,搜索用时 125 毫秒
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为了解决拖拉机驾驶室中频噪声问题,基于有限元-统计能量分析(FE-SEA)建立了某拖拉机驾驶室FE-SEA混合模型,通过理论计算和试验方法获取驾驶室模态密度、耦合损耗因子、结构内损耗因子数据,加载振动和噪声激励后进行FE-SEA联合仿真。将仿真获取的驾驶室声压级与实测数据进行对比,分析对比表明该模型在中频段利用FE-SEA混合法分析所得结果与试验测试值拟合程度较高。分析各子系统对驾驶室声腔的能量贡献度,确定对驾驶室噪声贡献较大的子系统,有针对性地对驾驶室声学包进行整改,获得一定降噪效果。 相似文献
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小波降噪提高时延估计精度的研究 总被引:1,自引:1,他引:0
为了估计两个在空间上分离的传感器所接收信号之间的时间延迟,结合小波降噪的特点,提出了一种基于小波降噪的广义相关时延估计算法.鉴于传统阈值降噪的不足,对小波阙值的选取进行改进,研究出一种新的小波阈值降噪技术.该算法克服了传统广义相关法需要信号和噪声先验知识的局限性,放宽了直接互相关法对信号和噪声的假设条件.仿真和实验结果... 相似文献
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在超声热应变成像(TSI)中,二维TSI图像中加热区域即感兴趣区域(ROI)的后方(远离声源方向)由于热声棱镜效应、互相关函数峰值误判等可能出现较强的噪声,影响对热区的识别。为对TSI图像降噪并优化ROI的选取,提出一种频域分割的复合超声热应变成像方法。首先,对加热过程中超声成像得到的射频数据进行频段划分,将划分后每个频段的数据视作一次独立成像的结果。其次,利用不同频段数据分别进行TSI计算,所得ROI的形态及其中的热应变分布有很好的一致性,而噪声分布差异较大。基于此对ROI与噪声区域进行区分,通过多频段TSI的复合实现降噪。最后,对降噪后的TSI图像,借助径向梯度指标实现ROI的识别。基于数值仿真和离体猪脂肪加热实验,对所建立的方法进行了验证,仿真中ROI热应变成像的对比度提升了1.7 dB,实验中提升了13.6 dB。 相似文献
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针对国内外缺少对振动轮噪声预估的问题,以某型振动轮为研究对象,首先基于动力学有限元理论对振动轮进行频率响应分析,其次采用声学边界元技术对振动轮辐射噪声进行了数值模拟,并通过实验验证了仿真结果的准确性,然后比较了垂直振动与圆周振动两种不同激振形式对辐射噪声的影响,得出垂直振动辐射噪声低的结论,最后对驾驶室声腔模态进行了仿真,与振动轮激振频率相近发生共振。通过调整激振频率,降低了司机耳旁噪声。所得研究成果可为振动轮辐射噪声的预估与改进提供一种切实可行的参考依据。 相似文献
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在分布式光纤传感系统定位中,传统时延估计算法常由于噪声相关性较强而失效。采用一种削弱相关噪声的改进型广义相关法,并针对系统特点,为进一步改善分布式光纤传感定位的准确度与稳定度,提出了一种先对数据按事件信号进行分帧,再采用卡尔曼滤波器对分帧时延估计结果进行跟踪的时延估计方案。系统仿真实验与实际数据测试结果均表明:提出的时延估计方案能够有效抑制强相关性的噪声,提高时延估计的准确度与稳定度。经大量现场测试,本文的方案能够有效地将时延估计误差稳定地控制在0.2个采样间隔以内,能够满足系统实际定位精度要求。 相似文献
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提出了一种基于空间像自适应降噪的投影物镜波像差检测方法。通过对空间像进行统计分析,获取空间像的噪声模型和噪声标准差模型。以噪声标准差为权重因子,利用加权最小二乘法对空间像进行主成分分解,可以实现对空间像的自适应、无损降噪,从而得到更为精确的主成分系数和泽尼克系数。使用光刻仿真软件PROLITH的仿真结果表明,在相同的噪声水平下,0.1λ像差幅值内,与基于空间像主成分分析的波像差检测技术相比,精度提高30%以上。在使用光刻实验平台测量Z8调整量的实验中,该方法的精度更高。 相似文献
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基于Gabor变换的TDLAS检测信号的降噪研究 总被引:1,自引:0,他引:1
可调谐二极管激光吸收光谱(TDLAS)技术结合波长调制光谱(WMS)技术是用于痕量气体检测的重要技术手段。通过锁相放大器进行谐波检测,对解调得到的二次谐波信号进行分析可获得气体吸收的信息。但由于二次谐波信号受到噪声的影响,降低了检测系统的精度和稳定性。为了提高TDLAS检测系统的信噪比(SNR),提出了一种基于Gabor变换对二次谐波信号进行数字滤波降噪的方法。以CH4在1 653.72 nm处的吸收光谱为例,通过仿真和实验对该降噪方法的有效性进行了验证。仿真结果表明,通过Gabor变换对信噪比为0dB的二次谐波信号进行处理后,系统的信噪比可提高15.73 dB。实验结果表明,基于Gabor变换进行降噪处理后,CH4浓度在0.001%~0.02%区间内与二次谐波峰值的线性相关系数r达到了0.996 59,且系统的检测精度和稳定性明显提高。 相似文献
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采用Kalman滤波方法进行钟差参数计算和预报时, 需确定Kalman滤波噪声协方差矩阵. 针对这一问题, 提出了一种新的卫星钟差Kalman滤波噪声协方差估计方法, 通过建立新息的相关函数序列与未知的噪声参数间的线性函数模型, 采用最小二乘法进行噪声参数估计. 采用精密钟差数据进行钟差参数估计和预报分析, 结果表明, 该方法具有较好的收敛性, 并与顾及随机噪声模型的开窗分类因子自适应抗差估计方法进行对比分析, 验证了新方法的正确性和有效性. 相似文献
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混沌信号协同滤波去噪算法充分利用了混沌信号的自相似结构特征,具有良好的信噪比提升性能.针对该算法的滤波参数优化问题,考虑到最优滤波参数的选取受到信号特征、采样频率和噪声水平的影响,为提高该算法的自适应性使其更符合实际应用需求,基于排列熵提出一种滤波参数自动优化准则.依据不同噪声水平的混沌信号排列熵的不同,首先选取不同滤波参数对含噪混沌信号进行去噪,然后计算各滤波参数对应重构信号的排列熵,最后通过比较各重构信号的排列熵,选取排列熵最小的重构信号对应的滤波参数为最优滤波参数,实现滤波参数的优化.分析了不同信号特征、采样频率和噪声水平情况下滤波参数的选取规律.仿真结果表明,该参数优化准则能在不同条件下对滤波参数进行有效的自动最优化,提高了混沌信号协同滤波去噪算法的自适应性. 相似文献
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The paper studies the dependence of the potential noise immunity of a detection system and noise immunity of a detection system with an interference compensator on the array parameters, angular signal position and local noise, the degree of correlation of distributed noise and spectral densities of the signal power, noise, and interference. The gain in noise immunity of the detection system when the optimal spatial filter is used with respect to the use of an interference compensator is estimated as a function of the degree of correlation of distributed noise and the power of random amplitude–phase errors of the weight coefficients of the array. 相似文献
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为同时滤除图像中的椒盐噪声和高斯噪声,提出了一种基于小波变换的混合噪声自适应滤除算法,该算法首先采用中值滤波去除椒盐噪声,然后借助边缘检测算子区将图像为分边缘与非边缘区域,进一步对非边缘区域引入改进的均值滤波器,有效削弱高斯噪声的同时保护图像边缘细节,既初步削弱高斯噪声又保护了边缘,最后采用改进的小波阈值滤波算法,对不同的小波系数采用不同的阈值函数,通过线性回归得到各最优阈值关系式。实验结果表明,该混合噪声自适应滤除算法能有效滤除椒盐噪声和高斯噪声,在图像主观质量和客观质量上均取得了较好的效果,能提高去噪图像峰值信噪比0.5~2.0 dB。 相似文献
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次声降噪系统对提高次声监测能力具有重要作用,为分析次声降噪系统阵列结构参数变化对其降噪性能的影响规律,构建玫瑰型(rosette)管道滤波器降噪系统声电等效模型,进而利用风噪声模型和仿真数据对该模型的单进气口传递函数和系统降噪性能进行了定量分析,总结了不同阵列结构参数对该系统降噪性能的影响规律,最后对国际监测系统(International Monitoring System,IMS)玫瑰型管道滤波器的降噪性能进行了评估。仿真实验及分析结果表明:(1)进气口数量约取96,阵列尺寸约18 m,一、二级管内径取10~20 mm,一、二级合成腔体积不得超过1 L,系统能获得较好的降噪性能;(2)IMS玫瑰型管道滤波器符合最佳阵列参数设置要求;(3)满足最佳阵列参数设置的玫瑰型管道滤波器可大幅度地提高信噪比。该分析结果可为已有次声降噪系统提供性能评估,可对新的次声降噪系统设计提供参考。 相似文献
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A recently proposed noise reduction system intended to facilitate the assessment of click-evoked otoacoustic emission (CEOAE) in noisy environments [Comput. Biol. Med. 30, 341 (2000)] is evaluated using 13 normally hearing ears and 9 ears with a sensorineural hearing loss. The noise reduction system is based on an adaptive noise canceller design using an additional noise-only reference microphone and intended to reduce externally generated noise. The system is tested in quiet and at different levels of white noise. The three main design parameters of the noise reduction system (adaptation time constant, length of the adaptive filter, and position of the noise reference microphone) are varied systematically in different experiments. With the noise reduction system active, CEOAE can be assessed correctly at noise levels which are 5 to 9 dB higher than without the noise reduction system. For the range of adaptation time constants considered (65.6 to 656 ms), no statistically significant effect on the amount of noise reduction is observed. Noise reduction is highest when the reference microphone is positioned close to the ear probe. Using this reference microphone position and adaptive filters of 6.56 ms in length, average noise reductions of 7.17 to 8.50 dB are achieved. 相似文献
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In this paper an analysis method and corresponding analytical tools for design of the experimental imaging payload (IMPL) of a remote sensing satellite (SINA-1) are presented. We begin with top-level customer system performance requirements and constraints and derive the critical system and component parameters, then analyze imaging payload performance until a preliminary design that meets customer requirements. We consider system parameters and components composing the image chain for imaging payload system which includes aperture, focal length, field of view, image plane dimensions, pixel dimensions, detection quantum efficiency, and optical filter requirements. The performance analysis is accomplished by calculating the imaging payload's SNR (signal-to-noise ratio), and imaging resolution. The noise components include photon noise due to signal scene and atmospheric background, cold shield, out-of-band optical filter leakage and electronic noise. System resolution is simulated through cascaded modulation transfer functions (MTFs) and includes effects due to optics, image sampling, and system motion. Calculations results for the SINA-1 satellite are also presented. 相似文献
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D Burshtein 《The Journal of the Acoustical Society of America》1992,91(3):1531-1537
The well-known speech production model is considered, where the speech signal is modeled as the output of an all-pole filter driven either by some white noise sequence (unvoiced speech) or by the sum of a periodic excitation and a noise sequence (voiced speech). Approximate maximum-likelihood (ML) estimation algorithms for the unvoiced case are well known. The ML estimator of the parameters is obtained for the voiced speech model. These parameters consist of the parameters of the periodic excitation (pitch parameters) and the parameters of the filter [linear prediction coefficient (LPC) parameters]. The results of the application of the algorithm on simulated and on real speech data are presented. 相似文献
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A method for optimizing the strength of a parametric phase mask for a wavefront coding imaging system is presented. The method is based on an optimization process that minimizes a proposed merit function. The goal is to achieve modulation transfer function invariance while quantitatively maintaining final image fidelity. A parametric filter that copes with the noise present in the captured images is used to obtain the final images, and this filter is optimized. The whole process results in optimum phase mask strength and optimal parameters for the restoration filter. The results for a particular optical system are presented and tested experimentally in the laboratory. The experimental results show good agreement with the simulations, indicating that the procedure is useful. 相似文献