AN INVESTIGATION OVER THE CORRELATION OF EAR CANAL RESONANCE AND TYMPANIC MEMBRANE IMPEDANCE ACCORDING TO AGE AND PHYSIQUE AND THEIR CHANGES AFTER DEATH

The human temporal bone preparation is an acknowledged model for resea rch of the physical processes affecting the outer ear canal and eardru m. Changes affecting the oscillation and resonance behavior of the tym panic membrane and ear canal between death and temporal bone preparati on presently exist in only a few studies. Since the influence of age a nd physique,as well as the width of ear canal on the ear canal resonan ce may be important, we prepared two separate studies to analyze these questions. The goal of our first test series involved children and wa s devised to determine if changes in the outer auditory canal resonanc es differed according to age. In so doing, canal resonance was recorde d with a real ear measurement system. Further, we recorded middle ear pressure, impedance of the tympanic membrane, ear canal volume, height , weight and surface of the body, head and ear size. We found a signif icant decrease in the resonance frequency of the outer ear which was a ge-dependent and was 2.75 kHz in the 7-year-old child. In a separate s tudy we wanted to know if results found in the postmortem temporal bon e reflected in vivo relationships. A tympanometer and real ear measure ment system was used to test the resonance behavior of the auditory ca nal as well as the vibration of the eardrum in dependence on temperatu re and the time after death for 9 h. We then proved the absence of sig nificant changes in the auditory canal and eardrum oscillation in this time period before possible postmortem changes occurred. Our findings show that the method of bone preservation after its preparation is de cisive for the validity of measurements in the isolated human temporal bone.