Electronic speckle pattern interferometric measurements of the basilar membrane in the inner ear.

A setup incorporating electronic speckle pattern interferometry, reference beam phase modulation, chopped laser light, and a simple microscope has been used to observe vibrations of the basilar membrane in human temporal bones. A postmortem effect ensures that no special treatment of the semitransparent membrane is required. Amplitudes (down to 20 A) and phases of the membrane motion are analyzed both in real time and video recordings. Observations include phase variations across the membrane and motions of Mossbauer sources (pieces of cobalt) on the membranes.