Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Signal Processing in High-End Hearing Aids: State of the Art, Challenges, and Future Trends | EURASIP Journal on Applied Signal Processing 2005 18 2915-2929 2005 V. Hamacher et al. Signal Processing in High-End Hearing Aids State of the Art Challenges and Future Trends V. Hamacher J. Chalupper J. Eggers E. Fischer U. Kornagel H. Puder and U. Rass Siemens Audiological Engineering Group Gebbertstrasse 125 91058 Erlangen Germany Emails Received 30 April 2004 Revised 18 September 2004 The development of hearing aids incorporates two aspects namely the audiological and the technical point of view. The former focuses on items like the recruitment phenomenon the speech intelligibility of hearing-impaired persons or just on the question of hearing comfort. Concerning these subjects different algorithms intending to improve the hearing ability are presented in this paper. These are automatic gain controls directional microphones and noise reduction algorithms. Besides the audiological point of view there are several purely technical problems which have to be solved. An important one is the acoustic feedback. Another instance is the proper automatic control of all hearing aid components by means of a classification unit. In addition to an overview of state-of-the-art algorithms this paper focuses on future trends. Keywords and phrases digital hearing aid directional microphone noise reduction acoustic feedback classification compression. 1. INTRODUCTION Driven by the continuous progress in the semiconductor technology today s high-end digital hearing aids offer powerful digital signal processing on which this paper focuses. Figure 1 schematically shows the main signal processing blocks of a high-end hearing aid 1 . In this paper we will follow the depicted signal flow and discuss the state of the art the challenges and future trends for the different components. A coarse overview is given .