Some studies indicate that the upper frequency limit of hearing is determined by the diameter of the eardrum. The wavelength of the sound wave and the diameter of the eardrum are approximately equal at this upper limit. If this is so, what is the diameter of the eardrum of a person capable of hearing $2.0 \times 10^{4} \mathrm{Hz}$ ? Assume $378 \mathrm{m} / \mathrm{s}$ is the speed of sound in the ear.