Multiple probe frequency acoustic reflex measurements

Acoustic reflex impedance measurements are made on forty-seven normal and two otosclerotic ears using fixed probe frequencies from 220 to 2000 Hz. In general, the reflex increases the middle ear impedance up to 700 Hz probe frequency and decreases it thereafter. It is postulated that this characteristic is related to removal of the cochlear fluid resistance due to stapes decoupling. At one probe frequency in the range 500--900 Hz, the reflex of 50% of the normal ears has either a diphasic pattern or shows no change in the impedance vector length. The accompanying phase change is always monophasic. In the otosclerotic ear the diphasic reflex is present for every probe frequency. These factors should be taken into account when probe frequencies greater than 220 Hz are used for reflex measurement.