Analysis Of The Acoustic Vibration Of The Pipa For The Evaluation Of The Quality

At present,the research on musical instruments at home and abroad is mainly focused on the structure of musical instruments and musical instrument playing skills,but less on musical instruments acoustics.Pipa,as the most representative national musical instrument in our country,has a long history,beautiful timbre and is loved by the masses.However,at present,the study of pipa is mainly focused on the structure and playing skills of the pipa.There is little research on pipa acoustics.Because at present the quality of pipa can only be distinguished by experienced manufacturers and performers,it is difficult to ensure that the pipa manufactured from the factory meets the standard,which also limits the quality of pipa to mass production and thus restricts the further development and spread of pipa culture.Therefore,it is very important to study the acoustics of pipa and establish the testing system of pipa quality.In this paper,firstly,the string vibration of pipa is studied,then the string vibration is analyzed by finite element method.Finally,the audio signal of pipa is analyzed,and some objective physical parameters related to the quality of pipa sound are found out.So as to establish the system of quality discrimination of pipa.First of all,according to the theory of vibration,the transverse vibration of pipa string is studied and analyzed when the "pick" and "spring" finger method is adopted,and the vibration equation of the pipa string is established when the pipa string is "played" and "picked" when the "pick" and "pick" finger method is used.According to the relationship between the chord length and the frequency of the tone,the length of the string of the pipa from the end of the string to the different pieces of the pipa is measured,and the pitch frequency of the empty string of the one string of the pipa is found out,thus all the four strings of the pipa are calculated.The pitch frequency value corresponding to the phonetics.The pitch frequency values of the same tone on different strings are compared to verify whether the pitch frequency values obtained from the theoretical calculation are correct.According to the tension of the lute string The vibration formula between T and its pitch frequency value is used to calculate the tension value of the four strings of pipa in order to prepare for the finite element analysis.Secondly,according to the tension value of the four strings calculated by the vibration formula and the measured parameters,the vibration of the pipa string is analyzed by using the harmonic response analysis in the finite element method.A program is written to analyze the vibration of four strings of pipa,and the pitch frequency values of all different strings and corresponding notes are analyzed.The theoretical calculated pitch value and the finite analysis pitch frequency value are compared and analyzed to verify whether the theoretical calculated pitch frequency value is correct or not.Finally,the pipa sound signal is collected and analyzed in MATLAB software.Firstly,a series of pre-processing such as sampling,de-noising,expected aggravation and so on are carried out on the sampled pipa sound signal,and then the preprocessed sound signal is analyzed in time domain,frequency domain,pitch detection and spectral centroid detection.The pitch frequency value obtained from the theoretical calculation and the pitch frequency value obtained from the finite element analysis are compared with the pitch frequency value obtained from the sound signal analysis in MATLAB,and then the previous theoretical calculation is verified.The results of the finite element analysis are correct or not.From these analyses,the objective physical parameters related to the quality of pipa sound,which are found in the calculation,are found to establish the discrimination of pipa quality.Comprehensive discrimination system.