Research On Music Perception Coding Strategy And Electrode Structure Of Cochlea Implant

Cochlea Implant(CI)is the only medical device that could help deep sensing deafness patients rebuild their hearings.Its working principle is to convert acoustic signals into electrical impulses to stimulate the auditory cochlear auditory nerve and allow the patient to obtain partial hearing.At present,the speech communication ability of cochlear implant patients in a quiet environment has been greatly improved,but the bad music perception effect is a difficult problem to be solved.The key issue of musical perception is that cochlear implant patients can hardly perceive accurate pitches.The pitch perception theory of the human ear has time theory and location theory.The time theory is reflected in the rate of electrical stimulation,and the location theory is reflected in the distribution of electrodes.A large number of studies start with improving the expression of time fine structure to enhance the perception effect of music,but the improvement effect is not obvious.After analyzing the characteristics of music signals,based on the location theory,the number and arrangement of electrodes also need to be improved.Firstly,this paper systematically analyzed the characteristics of music signals in detail,including basic features such as pitch and timbre,as well as the twelve equal temperaments and common representative musical instruments,thus establishing a comprehensive and concrete understanding of music acoustic signals.Then,the theory of cochlear pitch perception was analyzed,and the structure of the cochlear implant system was also introduced,which laid the theoretical foundation for the subsequent evaluation of audiometry and the improvement of the electrode design.The audiometric evaluation experiment adopts the method of signal reconstruction and convenes the subjects to perform subjective assessment tests.Based the location theory of pitch perception,the relationship between the harmonic components of music signals and pitch perception is explored.The experiment found that,the fundamental wave is the most important harmonic component of the note signal,and the absence of the fundamental frequency will significantly affect the perception of pitch and timbre.In order to obtain the ideal music perception effect,we must first express the fundamental wave accurately and transmit as many harmonic components as possible to ensure the spectral integrity of the music signal.In addition,according to the arrangement of the conventional cochlear electrodes,the harmonic components cannot accurately stimulate the corresponding frequency position of the basement membrane,resulting in harmonic frequency shift.The results of the audiometry show that the recognition effect of the synthesized melody signal according to the conventional electrode arrangement is not good.According to the relevant results of the audiometric evaluation experiment,the traditional cochlear implant electrodes are improved,and a method of arranging the electrodes at the corresponding positions of the basilar membrane of the cochlea according to the fundamental frequency of the musical notes is proposed.In the frequency range of 100 to 8000 Hz,considering the process limitations,note grouping is adopted,and the number of electrodes is appropriately increased in the bilateral cochlea.This electrode distribution method,in accordance with the characteristics of note distribution,is expected to enhance the perception of musical signals.