Reconstructive surgery for middle ear deafness has to deal with two acoustic principles: (1) construction of a new system of sound-pressure transformation to the oval window and (2) protection of the round window against air-borne sound waves.
The transformer function of the intact middle ear is achieved by two mechanisms: (1) hydraulic pressure ratio, based on the difference between the surface areas of tympanic membrane and footplate of the stapes, and (2) lever action of the ossicular chain. Retaining of the hydraulic pressure ratio (e.g., by columella transmission) is one of the main goals of reconstructive surgery of the middle ear. On the other hand, the ossicular lever action is not of any great importance (ratio of 1.3:1, according to Békésy, which increases the hearing by 2.5 db.). Besides, it does not play any role in our considerations, as it is connected with the functioning of an intact ossicular chain
SZPUNAR J. Differences in Hearing After Total Tympanoplasty Due to Presence or Absence of Crura of Stapes. AMA Arch Otolaryngol. 1960;72(1):96–101. doi:10.1001/archotol.1960.00740010100017
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