改进的变步长最小均方误差电子耳蜗语音增强算法

针对外部强噪声环境下电子耳蜗语音质量受损、适应性差等问题，提出了基于谱减法和变步长最小均方误差（LMS）自适应滤波算法联合去噪的改进方法，并以该方法构建了一个电子耳蜗前端语音预处理系统。利用变步长LMS自适应滤波算法输出误差的平方项来调节步长，采用步长值固定与变化相结合的方法，解决了自适应滤波算法收敛速度慢、稳态误差大的问题，适应性得到提高，提高了语音信号通信质量。该系统以TMS320VC5416和音频编解码芯片TLV320AIC23B为核心，通过多通道缓冲串口（McBSP）和串行外设接口（SPI）实现了语音数据的高速采集和实时处理。实验仿真和测试结果表明该算法消除噪声性能好，信噪比在低输入信噪比情况下提高约10 dB，语音质量感知评价（PESQ）分值也得到较大提高，能有效提高语音信号质量，且该系统性能稳定，能进一步提高耳蜗前端语音的清晰度和可懂度。

Speech enhancement algorithm based on improved variable-step LMS algorithm in cochlear implant

In order to improve the quality of speech signal and adaptability of cochlear implant under strong noise background, an improved method was proposed based on the combination of spectral subtraction and variable-step Least Mean Square error (LMS) adaptive filtering algorithm, and a speech enhancement hardware system for cochlear implant was constructed with this method. Concerning the problem of slow convergence rate and big steady-state error, the squared term of output error was used to adjust the step size of variable-step LMS adaptive filtering algorithm; besides, the combination of fixed and changed values of step was also considered, thus improved the adaptability and quality of speech signal. The speech enhancement hardware system for cochlear implant was composed of TMS320VC5416 and audio codec chip TLV320AIC23B, high-speed acquisition and real-time processing of voice data between TMS320VC5416 and TLV320AIC23B were realized by the interface of Muti-channel Buffered Serial Port (McBSP) and Serial Peripheral Interface (SPI).The Matlab simulation and test results prove that the proposed method has good performance in eliminating noise, the Signal-to-Noise Ratio (SNR) can be increased by about 10 dB in the case of low input SNR, and Perceptual Evaluation of Speech Quality (PESQ) score can be also greatly enhanced, the quality of the voice signal is improved effectively, and the system based on the proposed algorithm has stable performance which further improves the clarity and intelligibility of voice in cochlear implant.