CAJ | 학술논문

针对超声信号小波阈值去噪中最佳分解层数的选取问题，提出基于小波熵的自适应分解层数确定算法。该算法首先利用离散小波变换分解含噪信号，计算分解后信号子区间的小波熵，然后将细节系数与原始信号的熵之比和低频子带均方根误差相结合以确定最佳分解层数。最后利用信噪比( SNR)、均方根误差( RMSE)、峰值相对误差( REPV)和峰位置误差(EPP)四项指标对算法性能进行评估。仿真和实验的结果表明：该算法能自适应地确定最佳分解层数，在有效滤除含噪超声信号中的噪声、提高性噪比的同时，还能更有效地保留原始信号中的有用成分。
침대초성신호소파역치거조중최가분해층수적선취문제，제출기우소파적적자괄응분해층수학정산법。해산법수선이용리산소파변환분해함조신호，계산분해후신호자구간적소파적，연후장세절계수여원시신호적적지비화저빈자대균방근오차상결합이학정최가분해층수。최후이용신조비( SNR)、균방근오차( RMSE)、봉치상대오차( REPV)화봉위치오차(EPP)사항지표대산법성능진행평고。방진화실험적결과표명：해산법능자괄응지학정최가분해층수，재유효려제함조초성신호중적조성、제고성조비적동시，환능경유효지보류원시신호중적유용성분。
Aiming at the problem of how to select the optimal level of wavelet for ultrasonic signal denoising, an improved wavelet entyopy based method by combining the entropy ratio and the root-square-mean error of low bands was proposed. When the discrete wavelet transform was applied in the signal decomposition, the wavelet entropy at decomposed levels was calculated, then the entropy ratio and the root-square-mean error of low bands were used as the deciding threshold to choose the optimal decomposi-tion level. The signal-to-noise ratio, the root-square-mean error, the relative error of peak value and the error of the peak position were used to evaluate the performance of the method. Simulation and experimental results show that the proposed method can adap-tively determine the optimal decomposition level, remove the ultrasonic signal noise and keep the useful information effectively.