Research of Frequency Characteristics of Middle Ear Ossicles Implants

Abstract

The paper considers the means to restore human hearing in cases where hearing impairment does not affect the auditory nerve. Then the restoration of hearing is carried out by tympanoplasty - by replacing (restoring) the eardrum or chain of auditory ossicles. The paper examines implants made of bioreplaceable materials that differ greatly in their mechanical properties. Therefore, for the individual selection of ossicular implants in tympanoplasty, a physical model of implants was developed. Based on it, such an important parameter of implants as the value of their resonant frequencies is determined. It was found that the first resonant frequency for a cartilage implant is 61.1 MHz, and for a titanium implant - 487.2 MHz. The paper also compares the theoretical values   of the resonant frequencies of implants with the experimental results of their measurement using the original installation. The acoustic part of the experimental setup was an electroacoustic emitter placed on an acoustic vibration absorber (paralon) and a sensitive microphone placed on a counterweight to reduce the pressure on the oscillary prosthesis during measurements and fix it. Signal from the laptop was fed to amplify the input of the audio interface, and from its output signal was sent to the electroacoustic emitter. Between the electroacoustic emitter and the microphone, through the additionally developed and manufactured duralumin nozzles, which provided the introduction of sound vibrations in the prosthesis at angles of 15, 30, 45, 60, a sample of the oscillary prosthesis was recorded. With the help of the installation, the transfer coefficients of samples of ossicular prostheses made of Teflon, titanium, cartilage and bone tissues were measured and compared. It is established that for high frequencies the level of transmission coefficients decreases faster with increasing angle than for low ones, due to the increase in the acoustic size of prostheses with increasing frequency. Also due to the general decrease in the signal level with increasing angle, you can see a decrease with a center frequency of 1 kHz. It is established that at the angle of incidence of the acoustic wave 30, for all samples of prostheses, at a frequency of 4 kHz there is a rise in frequency response. Moreover, for a titanium prosthesis, the value of the transmission coefficient at an angle of incidence of 30 at this frequency exceeds the value of the direct incidence of the acoustic wave.