IN THE performance of a bone conduction test the bone conduction tip is placed over the mastoid bone. This position of the bone conductor tip gives a theoretic constant. If all mastoid bones conducted sound waves equally well the bone conduction test would give a true estimation of the condition of the cochlea being examined, but the air cell structures of human mastoids vary as to the size, number and distribution of the cells through the bone, and conduction through different types of mastoid bones must vary greatly. The sclerotic mastoid bone cannot have the same function as the normal pneumatic mastoid bone, and sound conduction through the different types of mastoid bones must vary as much in intensity on reaching the cochlea of the ear being tested as the structure varies in the mastoids through which these sounds must pass.
Clinical observations indicate that bone conduction tests may be
MacDONALD PG. BONE CONDUCTION THROUGH THE AUDITORY OSSICLE CHAIN. Arch Otolaryngol. 1950;51(5):641–654. doi:10.1001/archotol.1950.00700020666001
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