Compression techniques in digital hearing aids

• Κύριος συγγραφέας: Γαρίνη, Νικολέτα
• Άλλοι συγγραφείς: Μουστακίδης, Γεώργιος
• Μορφή: Thesis
• Γλώσσα: English
• Έκδοση: 2009
• Θέματα: Compression; Frequency domain; Συμπίεση; Συχνοτικό πεδίο; 617.89

There has been explosion in the number of digital hearing aids on the market in the last five years. This master thesis deals with some basic issues related to Digital Hearing Aids and more specifically, with the matter of compression in hearing aid devices. The classic frequency-domain compression uses FFT processing and the ideal and practical FFT systems are described. The underlying theory of Multirate Filter Banks and the Polyphase Decomposition as an efficient way of implementing them are presented. A different prototype filter design is thoroughly described and is proposed since it provides a minimum combined approximation error. Moreover, the approximation of the time-domain post filter with gain coefficients being adapted at the frequency domain is done by an all pole filter of lower degree. The simulation results provide us an evaluation of the proposed technique. Our contribution has been the design of a low-delay FIR filter which is extremely crucial for real-time speech processing applications.