Vibration properties of the ossicle and cochlea and their importance for our hearing system

The investigations of movements of the eardrum and stapes have shown that at higher frequencies, complex spatial vibration patterns occur in which the individual elements move in very different spatial directions and phase angles. For the stapes, such movements can be divided into piston-like and rotational movements around its short and long axis (tilting or rocking motions). Unlike the piston-like vibrations, rotational rocking motions do not lead to a net volume displacement of cochlear fluid at a certain distance from the footplate. Therefore, according to the current theory of hearing, it is assumed that such tilting movements have no effect on hearing. A number of studies have shown, however, that tilting motions can lead to cochlear activity. Further research is needed to quantify this effect.