When sound travels from one medium (air) to another (in this case, the eardrum), the frequency of the sound wave remains unchanged, but the speed and wavelength will change because the properties of the two mediums are different.
Since sound travels more slowly in air than in denser materials (like the tissues of the eardrum), the speed increases when it travels into the eardrum, and the wavelength will adjust accordingly.
Thus, the correct response is: Neither the frequency nor the wavelength of the sound change.