tailieunhanh - báo cáo hóa học: " Semitone frequency mapping to improve music representation for nucleus cochlear implants"

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: Semitone frequency mapping to improve music representation for nucleus cochlear implants | Omran et al. EURASIP Journal on Audio Speech and Music Processing 2011 2011 2 http content 2011 1 2 D EURASIP Journal on Audio Speech and Music Processing a SpringerOpen Journal RESEARCH Open Access Semitone frequency mapping to improve music representation for nucleus cochlear implants Sherif Abdellatif Omran1 2 Waikong Lai1 Michael Buchler1 and Norbert Dillier1 Abstract The frequency-to-channel mapping for Cochlear implant CI signal processors was originally designed to optimize speech perception and generally does not preserve the harmonic structure of music sounds. An algorithm aimed at restoring the harmonic relationship of frequency components based on semitone mapping is presented in this article. Two semitone Smt based mappings in different frequency ranges were investigated. The first Smt-LF covers a range from 130 to 1502 Hz which encompasses the fundamental frequency of most musical instruments. The second Smt-MF covers a range from 440 to 5040 Hz allocating frequency bands of sounds close to their characteristic tonotopical sites according to Greenwood s function. Smt-LF in contrast transposes the input frequencies onto locations with higher characteristic frequencies. A sequence of 36 synthetic complex tones C3 to B5 each consisting of a fundamental and 4 harmonic overtones was processed using the standard Std Smt-LF and Smt-MF mappings. The analysis of output signals showed that the harmonic structure between overtones of all complex tones was preserved using Smt mapping. Semitone mapping preserves the harmonic structure and may in turn improve music representation for Nucleus cochlear implants. The proposed semitone mappings incorporate the use of virtual channels to allow frequencies spanning three and a half octaves to be mapped to 43 stimulation channels. A pitch difference limen test was done with normal hearing subjects discriminating pairs of pure tones with different semitone intervals which were processed by a vocoder