WHEN a normal ear is exposed to a loud sound, the stapedius muscle in each ear will contract. This stapedius muscle reflex may be detected by a range or different procedures: (1) electromyographic registration by means of electrodes in the muscle or tendon; (2) optical detection by direct inspection of the eardrum or structures visible through a perforation in the eardrum; (3) measurement of changes in the sound transmission of the middle ear by recording of cochlear microphonics or recording of sound pressure in the external ear canal when sound is applied to the skull; (4) registration of changes in the acoustic impedance of the ear; (5) detection of variations in air pressure in the ear canal caused by eardrum movements.
Investigation of the latency of the stapedius muscle reflex may also be performed by most of the above-mentioned procedures. This latency is defined as the time interval between the
NEERGAARD EB, RASMUSSEN PE. Latency of the Stapedius Muscle Reflex in Man. Arch Otolaryngol. 1966;84(2):173–180. doi:10.1001/archotol.1966.00760030175011