Design Of Portable Otoacoustic Emission Detecting Instrument

Otoacoustic emission is a kind of audio energy, which produced in thecochlea and release to the external auditory canal through the ossicular chain andtympanic membrane. The discovery of otoacoustic emission reveals that thecochlea not only able to feel and distinguish surrounding voice, but also make asound spontaneously. The clinical implications of otoacoustic emission is that, itprovides us with a method of testing the magnifying function of cochlea and theintegrity of outer hair cell function. But otoacoustic emission detectinginstruments researched in our country are few functions and the technology isimmature, and that those researched by other countries are expensive and not suitfor spread. Aiming at these shortcomings, this paper design a portableotoacoustic emission detecting instrument, which has multi-functions and cost-effective.This otoacoustic emission detecting instrument use ATmega128as the corecontroller, which is a new type of high-grade MCU and researched by ATEML,and based on it finished the design of hardware and software systems of thewhole testing system. At the aspect of hardware system, the sound stimulationsection has three modules: digital to analog converter, audio power amplifier andprobe, and the signal processing section also has three modules: instrumentationamplifier, filter and program-controlled amplifier. At the aspect of softwaresystem, in order to obtain the results of transient evoked otoacoustic emissionand distortion product otoacoustic emission, we use many methods such assynchronous accumulated, coherent average, add cosine window, fast fouriertransform algorithm and so on, to process the data acquired by analog to digitalconverter.This otoacoustic emission detecting instrument has finished the function ofdetecting transient evoked otoacoustic emission and distortion product otoacoustic emission. It not only can supplied by the USB interfaces of computer,work together with PC software through its USB to asynchronous serial datatransfer module, but also can work without PC, supplied by battery, controlled bykeyboard, and use liquid crystal display as terminal, thus it is convenient to carry.Finally, this paper use the otoacoustic emission detecting instrument domany experiments, while finish the design of hardware circuit and softwarearithmetic. Then confirmed the feasibility of this design through the experimentalresults and waveforms.