Using principles of leverage the Middle ear amplifies the sound signal.
The amplification mechanism works on the same principle as my car jack. Leverage is the name of the game. First of all, the Tympanic membrane, which initially receives the sound has a larger surface area than the third ossicle (Stapes) which imparts the signal to the Inner Ear. This acts to concentrate the energy at this point.
Also the special arrangement of the three ossicles, which form a bridge between the tympanic membrane and the middle ear, also provides leverage.
The Tympanic membrane itself has a convex shape toward the outside, which acts to gather and concentrate the energy of the sound as it is transmitted to the first ossicle (Malleus) which is attached to the membrane.
In addition to the Tympanic membrane and the three ossicles, the Middle Ear includes some other important structures.
One is the Middle Ear Cavity which houses the three ossicles. This is a cavity filled with air.