Remote masking in presbycusis.

Remote Masking (RM) (a rise in threshold for low-frequency tones when the ear is exposed to a high intensity noise band of high frequency) has been attributed to mechanical nonlinear distortion of the cochlear partition, as an effect of the envelope of a nonuniform signal. Clinical studies using RM have revealed RM is normal only when both the endolabyrinthine pressure and the cochlear hydrodynamics are normal. Increasing the stiffness of the cochlear partition affects adversely the mechanism of motion of the cochlear duct and reduces RM values. We studied RM in normal young Ss and in patients with presbycusis in order to determine whether aging of the inner ear also induces stiffness of the cochlear partition. In presbycusic Ss the RM values were indeed reduced symmetrically in both ears and progressively as a result of aging. Thus RM demonstrates the existence of cochlear conductive presbycusis and can be considered a useful test of stiffness of the cochlear partition.