Design And Implementation Of Sweep Otoacoustic Emission Rapid Detection System

The discovery of OAEs phenomenon is an important progress in the study of otology in recent years, OAEs is a very weak acoustic energy generated by the cochlea, it can objectively detect the function of cochlear, and therefore, it has a very wide range of applications in clinical otology and hearing screening. Currently, there already have some Otoacoustic emission testing equipments in the market; however, all of them have low detection efficiency, and can only detect several certain discrete frequency points. This article designed a sweep Otoacoustic emission testing system to extract the Distortion Product Otoacoustic Emission (DPOAE) signals; it can effectively solve the above problems.Firstly, the article discussed some concepts and characteristics of the Otoacoustic emission, introducing sweeping stimulus to replace the existing pure tone stimulus, making the Otoacoustic emission testing efficiency greatly improved. The system was composed of four modules:the generation of sweeping stimulus, the amplification of DPOAE signal、 filtering and collecting, the transmission of USB data and signal extraction and analysis; Using TI’s DSP chip TMS320VC5509A as the system CPU as well.Secondly, the article described the design of the adjustable dual-channel stimulus playing circuit; transform the stimulus data to the sound through the D / A conversion and power amplifier. The stimulus was used for inducing DPOAE signal; the paper put forward a "three-step" sweep stimulus playing combination, using linear transformation arithmetic filter out stimulus artifact. After DPOAE signal generated, the system got 24 high-precision signal finally by chose the amplification circuit amplifying signals, filtering circuit and A / D sampling circuit.Then, adopting the USB data interface, accomplish the USB firmware and PC software programming, achieved the transmission of sweep stimulus and A/D sampling signals; in other words, the PC transmit the sweep stimulus data to the DSP, DSP control the acquisition of DPOAE signal, then transferred to the PC and save the data.Finally, intercepted sweep stimulus and impulse noise by using the linear transformation and threshold filtering algorithms, got the time-frequency curve of DPOAE signal by short-time Fourier transform, and completed the performance tests of system stability and superiority.