基于邻域相关性多阈值新函数寻优法的小波降噪分析

Wavelet Denoising Analysis Based on an Optimization Method of Multi-threshold New Function with Neighborhood Correlation

  • 摘要: 为了更好地获取噪声影响下的原有信号,在邻域小波系数收缩的NeighCoeff方法基础之上,提出了一种邻域相关性多阈值新函数的小波降噪方法.该方法根据小波系数之间的相关性,将邻域窗口内所有小波系数的平方和的大小划分为邻域硬阈值、邻域窗口阈值和邻域扩张阈值.将这些邻域阈值与修正的通用阈值相比较,来实现窗口尺寸的自适应调节和小波系数的保留或收缩,以此达到消噪的目的.此外新函数的收缩因子能够较好体现与被滤波噪声的相互关系,可以进一步提高消噪的精度.然后将多阈值函数与修正的全局阈值相结合,利用混沌粒子群对邻域扩张阈值参数γ和修正的全局阈值参数α进行寻优,以获取最优小波系数的重构信号.所提方法与其它阈值函数去噪方法相比,其仿真结果表明在信号信噪比、降低有用信号失真和抑制噪声等方面都有一定的提高.

     

    Abstract: In order to better obtain the original signal under the influence of noise, on the basis of a shrinkage method of neighbouring wavelet coefficient called NeighCoeff, we propose a wavelet de-noising method based on multi-threshold new function with neighborhood correlation(MNFNC). According to the correlative characteristics of wavelet coefficients, MNFNC classifies quadratic sum of all wavelet coefficients in neighborhood window as neighboring hard threshold value, neighboring window threshold value and neighboring expansion threshold value. A comparison between these neighboring threshold values and the revised universal threshold achieves adaptive adjustment of window size and retention or shrinkage of wavelet coefficients, which is designed to remove noise. In addition, we use the shrinkage factors of MNFNC, which well reflect the relationship with the filtered noise, to decrease the effect of noise. Then, in combination with revised universal threshold, MNFNC uses chaotic particle swarm optimization algorithm to find the optimal values of parameters γ and α, which come from neighboring expansion and universal thresholds, respectively, in order to reconstruct the processed optimal wavelet coefficients to the original signal. We compare our proposed method with de-noising methods of other thresholding function, and the simulation results show MNFNC can improve the signal-to-noise ration, reduce distortion of the useful signal and effectively eliminate noise.

     

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