Design And Implementation Of Otoacoustic Emission Electronic Simulator

The phenomena and clinical applications of Otoacoustic emission has been one of the major parts in pediatric research recently. This acoustic detection method can be adopted in large scale of situations, such as hearing screening in new-born, monitoring under emergency and etc. It is widely utilized and accepted by people with various ages. Starting from2010, China has passed the regulation that every infant should have an acoustic examination on Otoacoustic emission within48hours after their birth.Examination based on Otoacoustic emission has already become a widely applied method in hearing tests worldwide. However, calibration of the Otoacoustic emission detector remains a conundrum. Up till now, publications are only about calibrating part of the detector instead of entire functional alignment. This thesis designed and realized a simulated Otoacoustic emission testing system, focusing on the problem currently faced by the equipment and achieved the function as an Otoacoustic emission detector.(1) Hardware. Core chip and main controller is TMS320F2812from TI, in cooperation with a high-speed and high-resolution digital audio processor TLV320AIC23B, a high-performance magnifying chip AD620, the major part for signal processing has been accomplished. This system is powered by a portable lithium battery and adopted energy saving method, providing different working voltage for various parts based on a power management chip.(2) Software. Based on real condition, the software system pre-allocatesperiodic signals which covers the entire frequency band for human Otoacoustic emission. Digital signal processing skills are applied to generate the signal. During signal receiving, temporal windowing are adopted to avoid alias, time domain correlation averaging are utilized to reduce the noise and improve the signal to noise ratio. Overall, mature signal processing methods are applied to deal with audio signals and expected results can be achieved.(3)Testing environment. First in simulating human ear condition, a2CC coupled cavity of artificial ear was made, which is able to simulate the real signal spread situation in human ears and guarantee the test environment is as close to the real condition as possible. In addition, censored box is made from a double panel structure, which are stainless steel plate, sound-absorbing cotton polyester amine, air sandwich, combined stainless steel plate and sound-absorbing cotton polyester amine from inside to outside. This sound reduction model is able to decrease the sound to35dBSPL under a40dBSPL level of input.Based on all the steps and modules above, Otoacoustic emission simulation and testing system is designed and realized. Expected results have been achieved, which is able to detect the signal precisely and calibrate the detector successfully.