| Summary: | 碩士 === 國立成功大學 === 電機工程學系 === 102 === In this thesis, a band-limited (BL) adaptive feedback cancellation algorithm (AFC) is proposed, and the BL frequency can be adjusted automatically. The proposed algorithm overcomes the limitation of traditional BL-filter-X AFC (BL-FX-AFC) and it can efficiently accommodate itself to the changed environment. We use a sliding discrete cosine transform (DCT) to realize the transform-domain least mean square algorithm (LMS), and adopt coefficient smoothing scheme and gain control method to improve the performance of feedback cancellation. The results show that the proposed AFC is better than basic AFC by 4.46dB in misalignment, 5.11dB in ASG, and 3.48dB in SFR while the spectrum power of feedback path concentrates on high-frequency band. Not like BL-FX-AFC, it can still cancel feedback noise without being out of control while the spectrum power of feedback path concentrates on low-frequency band. Therefore, it is very suitable for future applications in the area of hearing aids.
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