Theoretical Analysis On Acoustic Immittance Measures Based On An Analogical Model

Tympanometry involves measuring the acoustic admittance of the middle ear system as a function of air pressure in the external auditory meatus.Since tympanogram provides a noninvasive and objective evaluation of middle ear functions,it has gained a wide application in the ENT clinic.Traditionally,tympanometry was performed with a 226Hz probe tone and the tympanograms had a simple distinctive peak.Recently,with the application of high-frequency tympanometry and multifrequency,multicomponent tympanometry,the tympanogram shape becomes more varied.In this study,multifrequency tympanograms of the ear with a flaccid eardrum or otosclerosis and acoustic reflex responses with a 220 or 1000Hz probe tone were reproduced by Chen and Shen’s model adjusting different parameters,which were consistent with typical clinical results.Besides,a new approach to estimation of the admittance and length of the ear canal was proposed based on multifrequency,multicomponent tympanometry.It can help people understand the mechanism of tympanometry better in spite of some limitations and the lack of combination with clinical data.Wideband tympanograms were also simulated based on different models.The model results were in good agreement with the experimental results at low frequencies,whereas at high frequencies it became more complicated.The theoretical analysis on acoustic immittance measures could provide a better understanding of the mechanism of tympanometry and its clinical utility,and may help people with diagnosis and treatment on different middle ear diseases.