Dreidimensionale schwingungsmessungen im innenohr: Aufklärung der frequenzselektivität des gehörs

A novel measurement technique was developed to investigate the three-dimensional vibration of the microstructures in the hearing organ. The transverse vibration component was measured with a laser Doppler velocimeter coupled into an epifluorescence microscope. The horizontal components were recorded with an in situ calibrated photodiode-system which was mounted in the focal plane of the microscope. With this technique, a resonance in the motion of the tectorial membrane was found, which was located 0,5 oct below the best frequency of the cochlear partition. It is concluded that this resonance provides the necessary phase conditions to allow positive feedback of mechanical energy into the travelling wave by the outer hair cells, thereby amplifying and sharpening the cochlear response. This technique gives further insights into the understanding of the active sound processing of the inner ear and of hearing disorders.