The eardrum is displaced surprisingly little when a sound wave strikes it. Some idea of the displacement of the eardrum by a sound wave can be obtained by using Equation 7.1:The displacement amplitude, A, of the air molecules gives us a lower limit to the displacement of the eardrum. At the threshold of hearing at 3.8 kHz, the sound intensity is about 10–12Wm2. The threshold of pain begins at an intensity of 10Wm2 [19]. What is the amplitude of eardrum vibrations at these intensities?