Computerized laser Doppler interferometric scanning of the vibrating tympanic membrane.

The vibrational movements of the tympanic membrane (TM) of in vitro human specimens were studied by computerized laser Doppler interferometry. The versatility of the method for measuring the velocity of the vibrating TM was demonstrated by point measurements, horizontal sweeps, and three-dimensional scans of the entire TM. Single phases of the TM vibration were examined and plotted three-dimensionally. All information was stored digitally, making it possible to recreate the movements as in slow motion on the oscilloscope. The effect of coating the TM with a thin layer of magnesium oxide was studied. The repeatability of the method was demonstrated. TM vibrational patterns at different sound pressure levels and frequencies are displayed and discussed as also are the results of scanning the specimen in different positions.