The ipsilateral registered stapedius reflex is often reduced for intensity levels greater than 105 dB (SPL). Because of a reduced impedance, that is not influenced by the reflex arc, an "inverse" reflex curve can be registered. This phenomenon described by Lehnhardt et al. (1) as a "acoustic'mechanical effect" occurs without latency and interferes at levels higher than 105 dB (SPL) with the reflectory impedance change. This effect often dominates and causes a pronounced inverse ipsilateral reaction characterized by an impedance reduction. Frequently middle ears with a steep gradient of the tympanogram show an acoustic-mechanical effect. The missing reflectory component of the impedance change in deafness, in otosclerosis and in facial nerve disorders mostly causes an inverse impedance change. Investigations in temporal bone, in middle-ear models and from the middle ear of the guinea pig led to the assumption, that inverse impedance changes be related to coupling phenomenons of the tympanic-membrane and the ossicles. Excluding artifacts of the measuring device and investigating different states of the middle ear, it can be concluded, that these phenomenons are characteristic for intensity levels greater than 105 dB (SPL).