An Acoustic Bridge for Measuring the Static and Dynamic Impedance of the Eardrum

An acoustic impedance bridge is described that is capable of measuring the input impedance of the human ear in the frequency range of 250 to 1250 Hz, with an accuracy of 3 degrees and 5 percent in phase and magnitude, respectively. In addition to static impedance, the bridge measures and records both in-phase and quadrature components (re an arbitrary reference) of changes in the ear´s impedance due to the acoustic reflex. Assumptions upon which the use of the bridge is based are stated, the calibration procedure is described, and an example of the use of the bridge is given.