I would like to know the side effects of losing an eardrum.

T.B.

Let's start by considering how you hear.

Sound is a form of energy. Sound energy is received by the external ear; it travels down the ear canal, and causes the eardrum to vibrate. Partly embedded in the eardrum is a tiny bone called the "malleus." When the eardrum vibrates, the malleus vibrates. The malleus is connected to a tiny bone called the incus, and the incus is connected to an even tinier bone called the stapes. Sound energy passes from malleus, to incus, to stapes. The stapes vibrates in a piston-like manner atop a fluid-filled chamber, the cochlea (COKE-lee-uh if you are American, COCK-lee-uh if you are a Brit or an Aussie.) The cochlea has numerous cells (called "hair cells") that are sensitive to this vibration. Stimulation of the hair cells causes nerve impulses to travel to the brain via the auditory nerve.

Without an eardrum, the malleus will still vibrate in response to sound, but some sensitivity to sound will be lost. Thus, one consequence of an absent eardrum will be poorer hearing in that ear. Arguably, this is the most significant side effect of an absent eardrum.

Imagine a bongo drum. Tap the drum, and it produces sound. The drum head converts one form of energy (the tap) into another form of energy (sound). Now imagine putting a hole in the drum. Even a small hole will impair the ability of the drum to produce sound. As the hole becomes larger, you would have to hit the drum harder and harder to produce drumbeats of the same loudness. In other words, the efficiency of energy conversion is impaired by the hole.

Back to the eardrum. Sound is the "tap" the eardrum converts into another form of energy, the vibration of the three middle-ear bones. A small hole in the eardrum will impair this energy conversion very little. As the hole becomes larger and larger, the same loudness of sound will produce less and less vibration of the middle ear bones. The bigger the hole, the worse the hearing.

But this isn't the only role for the eardrum. The eardrum also acts as a barrier between the ear canal and the middle ear. (The middle ear is an air-filled space located behind the eardrum.) The middle ear is not usually exposed to the elements. If you have a sizable hole in the eardrum, any number of things can penetrate this space -- wind, water, dirt -- things that really shouldn't be there. This can lead to problems ranging from discomfort to outright pain and infection. People with large perforations often have to wear earplugs on windy days, and they almost always use earplugs when bathing in order to prevent ear infections.