隨著台灣人口不斷的高齡化，增進高齡人口的生活品質是一項重要的課題。利用助聽器可提升老年人在與人溝通時的語音理解能力，改善因溝通不良所帶來的負面影響，並維持良好的人際關係。本論文以適應性小波理論為基礎，設計數位助聽器。助聽器在設計上必須考慮語音的即時性及不同頻率所需的增益，小波理論的特性可符合上述的兩點需求。在系統設計時，重點放在環境噪音的偵測與濾除，尤其是在十分吵嘈的環境下，不適當的噪音濾除及音量放大，將造成助聽器使用者的不適。首先利用小波係數臨界法判斷信號中是否雜訊成分極高，若雜訊成分極高則判定為噪音，若雜訊成分不高，則使用Teager’s Operator計算出適應性時變臨界值，並利用此適應性時變臨界值進行細部信號判斷，最後依系統設定之信號判斷法則進行參數調整且輸出。研究結果顯示，系統可準確的偵測出環境噪音予以衰減，且依聽覺舒適的原則輸出聲音信號以避免助聽器使用者的不適。

　　Since there are more and more aged people in Taiwan, it is a very important issue to improve the quality of life of aged people. Wearing hearing aid system can promote the ability of catch what other people is speaking and reduce the influence of worse communication. Therefore, they can maintain good interpersonal relationships. In this paper, we design a digital hearing aid system based on adaptive threshold wavelet theory. In designing a digital hearing aid system, we must seriously concern about the real-time requirement of the speech. We must also care about that different gains must be used for different frequencies. The requirements can be easily achieved by using wavelet theory. In designing the system, the most important thing is to detect the environment noise and to decay it. Especially in a very noisy situation, unsuitable de-noising method will cause undesirable sound enhancement and make the hearing-aid users uncomfortable. First, wavelet coefficient threshold is used to detecting the signal composition. If the noise dominates the signal, this signal will be judged as noise. Second, Teager’s operator is used to calculating the time adaptive threshold values to detecting the detail signal composition. Finally, hearing-aid system adjusts parameters of the signal according to the judging procedure. According to the experimental results, the system can precisely detect the environment noise and decaying it. It also reduce the uncomfortable of hearing-aid users.

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