Noise reduction for hearing aids using digital signal processing

1.降噪算法已开发出一种用于降低平稳/非平稳环境噪声的算法，并通过计算机模拟进行了验证。此外，还利用信号处理系统构建了总体降噪系统。为了有效地抑制噪声，将自适应波束形成技术与传统的固定波束形成器相结合，以获得对平稳噪声和非平稳噪声的鲁棒衰减。另一方面，为了减小啸叫，引入了自适应反馈抵消器.评价所开发的系统已应用于真实的环境噪声，并在降噪量和其他问题方面进行了评价。结果表明：对于环境噪声，大功率的方向性噪声降低了20 dB以上，混响等非方向性噪声也降低了10 dB;对于啸叫，啸叫裕度提高了20 dB.语音清晰度的提高对受噪声污染的语音应用了降噪系统，并进行了听音测试。实验结果如下：在环境噪声抑制方面，通过引入该系统，语音可懂度从50%提高到70%。对于啸叫消除，常规的自适应反馈消除器破坏了诸如有声语音的周期性信号。然而，使用频率压缩器与自适应反馈消除器一起提出在我们的系统产生很少的腐败和对语音清晰度没有影响。

1. Algorithm for noise reduction An algorithm for reducing stationary/nonstationary environmental noise has been developed and has been verified via computer simulation. Moreover, total noise reduction system has been constructed using signal processing system. For ebvironmental noise reduction, an adaptive beamforming technique was combined with conventional fixed beamformer to obtain robust attenuation for not only stationary noise but also nonstationary noise. On the other hand, for reducing howling, adaptive feedback canceler was introduced.2. Evaluation The system developed has been applied to real environmental noise and was evaluated in terms of the amount of noise reduction and other issues. The results can be summarized as follows : As for the environmental noise, directional noise with large power was reduced by more than 20 dB,while nondirectional noise such as reverberation is also reduced by 10 dB.As for the howling, howling margin increased by 20 dB.3. Improvement in Speech Intelligibility Noise reduction system has been applied to the speech corrupted by noise, and the listening test was conducted. The results can be summarized as follows : As for the environmental noise reduction, the speech intelligibility was improved from 50 % to 70 % by introducing the proposed system. As for the howling cancellation, periodic signals such as voiced speech is corrupted by the conventional adaptive feedback canceler. However, use of frequency compressor together with adaptive feedback canceler as proposed in our system yields little corruption and no effect on speech intelligibility.