At the end of the ear canal, the sound waves hit the ear drum. The ear drum is a thin membrane between the outer ear and middle ear.
The ear drum is directly connected to the hammer bone. The hammer bone, along with the anvil and stapes, are the smallest bones in the human body. They transmit the mechanical vibrations of the ear drum into the inner ear.
The stapes transmits the vibrations via the oval window to the inner ear. In this way, the sound waves arrive in the cochlea, which is filled with fluid.