CAJ | 학술논문

针对现有语音增强方法在低信噪比下性能降低的问题，提出了一种自适应时移与阈值的离散余弦变换语音增强算法。首先，对软阈值函数进行改进，既能消除噪声主导帧中的噪声，也能消除语音主导帧中的噪声，并依据信噪比自适应地选择阈值，较大程度地保留了语音的原始特征。其次，依据基音周期自适应地选择分析窗时移，降低了固定分析窗时移产生的白噪声，并且引入短时自相关函数和短时平均幅度差函数相结合的加权自相关函数，来进行基音周期的检测，提高了基音周期检测的准确性和对噪声的鲁棒性。理论分析与仿真结果表明，该算法在信噪比低至-5 dB噪声环境下，相比现有的经验模态分解算法和子空间算法，输出信噪比有较大提高，鲁棒性更好。
침대현유어음증강방법재저신조비하성능강저적문제，제출료일충자괄응시이여역치적리산여현변환어음증강산법。수선，대연역치함수진행개진，기능소제조성주도정중적조성，야능소제어음주도정중적조성，병의거신조비자괄응지선택역치，교대정도지보류료어음적원시특정。기차，의거기음주기자괄응지선택분석창시이，강저료고정분석창시이산생적백조성，병차인입단시자상관함수화단시평균폭도차함수상결합적가권자상관함수，래진행기음주기적검측，제고료기음주기검측적준학성화대조성적로봉성。이론분석여방진결과표명，해산법재신조비저지-5 dB조성배경하，상비현유적경험모태분해산법화자공간산법，수출신조비유교대제고，로봉성경호。
In view of the limitation of the existing speech enhancement methods under a low SNR,this paper proposes a speech enhancement method using self-adaptive time-shift and threshold discrete cosine transform.First,with the improved soft-threshold function to deal with the discrete cosine transform coefficients,we can not only eliminate the noise of noise-dominant frames,but also eliminate the noise of signal-dominant frames;the threshold is also selected self-adaptively based on the SNR,which can largely retain the original characteristics of the speech.Secondly,the shift of the analysis window is self-adapted according to the pitch period, reducing the white noise of the fixed window-shift.And a weighted autocorrelation function is introduced for pitch detection combined by the short-time autocorrelation function and the short-time average magnitude separation function,improving the precision of pitch detection and robustness to noise.Theoretical analysis and simulation results show that the output SNR of this method has increased greatly and the robustness to noise is better when the input SNR is as low as -5 dB, compared with the empirical mode decomposition algorithm and the subspace algorithm.