Some Measurements of the Impedance at the Eardrum

Three methods are described for measuring the impedance at the eardrum. Two methods are psycho-physical and one is purely physical. Although the physical method seems to be more appropriate for this kind of measurement, all three methods yield comparable results. The final results agree with some of the measurements made in the past on the reactance at the eardrum up to 1000 cps. They disagree on reactance above 1000 cps and on resistance. The new data seem to fit the general picture of sound conduction in the ear better than did values obtained earlier. They could lead to corrections in the coupler cavities used for miniature earphones and in calculations the sound attenuation afforded by some ear protectors.