Design And Realization Of Calibration System For Otoacoustic Emission Measuring Instrument

OAE(Otoacoustic emission)is an audio energy produced in the cochlea,which is conducted by the ossicular chain and tympanic membrane.Currently,otoacoustic emissions has become one of the most basic objective and nondestructive means for testing hearing.In real life,acoustic emission is mainly applied to the research on auditory physiology,auditory disease diagnosis and newborn hearing screening.Due to that otoacoustic emission measuring instrument is audiometric equipment to detect OAE signals,it has become the basic acoustic measuring equipment,widely used in hearing screening.Obviously,performances of otoacoustic emission measuring instrument affect the physical and mental health of the hearing impaired directly.Therefore,in order to ensure the accuracy and unification of the data,the measuring instrument needs to be calibrated regularly.A calibration system for OAE Measuring Instrument is designed in this paper,it can calibrate the sound stimulation unit and the feedback measurement unit of otoacoustic emission measuring instrument.The main work of this paper is as follows.1.Building calibration system for otoacoustic emission measuring instrument based on the PXI and microcontroller development board.The calibration system can calibrate the sound stimulation unit and the feedback measurement unit of otoacoustic emission measuring instrument.In the calibration of sound stimulus,in order to obtain the performance parameters of a variety of sound stimulation,high-accuracy acquisition card of NI company is applied,which can realize the acquisition,processing and analysis of sound signals.In the calibration of the feedback measurement unit,generation and real-time output of DPOAE feedback and TEOAE feedback signal is produced by the acquisition card.2.In the software structure of the calibration system,modular design principle is introduced,the software has the features of high degree of automation and convenient operation,which can greatly improve the efficiency of the calibration work.The software structure is divided into 3 layers:underlying common module,function module and system module.The underlying common module is mainly used to package the driver and function.The function module is used to calibrate the parameters.The system module is used to complete the human-computer interaction.The modular design principle improves the maintainability of the whole system.3.Designing acoustic coupled cavity coupling otoacoustic emission measurement and calibration system based on IEC 60318.We verify the validity of the acoustic coupled cavity of through the finite element analysis method and experiment method.In order to realize the closed loop feedback calibration,we change the single microphone acoustic coupled cavity structure into the two microphone acoustic coupled cavity structure,which can receive sound stimulation from the otoacoustic emission measuring instrument and transmit the signal to the otoacoustic emission measurement.4.Experimental measurements and evaluation of measurement uncertainty.In order to verify the validity of the calibration system,we calibrate the full function of a certain type of diagnostic otoacoustic emission measurements,while we evaluate the uncertainty of the sound stimulus intensity.The experimental results show that calibration system can calibrate the performance parameters of the otoacoustic emission measuring instrument,After further improvement,the calibration system can be used to calibrate the OAE measuring instrument in the daily calibration...