Experimental Studies on the Effects of the Tympanic Membrane Perforation on Middle Ear Transmission / 听力学及言语疾病杂志

Objective The goal of the present study was to determine the effects of different location perfora-tions on the middle ear transfer functions by measuring the velocity and pattern of the tympanic membrane vibration in guinea pigs with intact and perforated TM .Methods A laser Doppler vibrometer was used to measure the sound transmission properties on the movement of the tympanic membrane on 6 fresh temporal bones of guinea pigs in the frequency range of 0 .5~8 kHz at 90 dB SPL .The velocity was measured at three points on the manubrium before and after a different location perforation was made with a 20-gauge needle(1 .1 mm diameter) .The locations of the perforations were in anterior -inferior quadrants of left ears and in posterior -inferior quadrants of right ears .And the velocity was measured from 6 poins with the intact tympanic membrane .Results The highest velocities were re-corded at the site of inferior umbo throughout the frequency range .The manubrium vibration velocity losses were noted in the perforated ears below 1 .5 kHz ,the velocity losses were smaller above 1 .5 kHz ,and the maximum ve-locity loss was about 7 dB at 500 Hz with the posterior -inferior quadrant perforation .Although there was a trend for anterior-inferior perforations to show a slighter loss than posterior -inferior perforations in velocity below 1 .5 kHz ,no statistical differences in velocity loss were found between different perforations .The average ratio of short process velocity to umbo velocity at all frequencies was approximately 0 .5 ,and the ratios were found no systematic differences before and after perforation at almost all frequencies from different perforations .Conclusion The manu-brium vibration velocity losses from TM perforation are frequency -dependent and the largest losses occur at the lowest sound frequencies .Different sites of small perforation have not any important effects on middle ear sound transmission .

Effect of Fixing Different Positions of the Wire Linked to FMT on FMT Vibration / 听力学及言语疾病杂志

Objective To find an optimum fixed position on the wire linked to floating mass transducer(FMT)by measuring FMT vibration with laser doppler vibrometer(LDV).Methods Fixing three points on the wire linked with FMT:10 mm,5 mm away from the FMT and the end of the wire.The vibration intensity of the FMT was measured with LDV when the FMT received continuous pure-tone stimuli at 100 and 80 dB SPL,respectively.Results The vibration amplitude of FMT was the highest at 1.5 and 2 kHz,and the lowest at 0.25 and 8 kHz when the FMT received pure-tone stimuli from 0.25 to 8 kHz.When the wire was fixed at/above different points,the FMT produced similar positive vibration amplitude.Conclusion The wire is fixed linked with FMT at/above three different points,FMT produces similar vibration amplitude when receiving pure tone stimuli.