Turning the corner on what passed as a trail in the great swamps of South Carolina, I spotted a bobcat. The feline was walking away and the wind favored a life-sized mount. I discreetly racked one in, shouldered the muzzle-braked rifle and BOOM! Well, not "boom" to me, I didn’t hear it go off as I was transfixed by the process. But two years later, my hunting partner Paul still hassles me about making him near deaf in his left ear as I neglected to call his attention to what was going on as he rounded the corner a half step behind.

It’s odd isn’t it, that so often we just don’t hear the blast when we're on game. Far less odd is that this altered perception does nothing to protect our hearing. Predictably we firearm folks are at a higher risk of traumatic hearing loss because of the "boom" we all love so much. The hearing loss from repeated trauma is usually so gradual that it isn’t noticed until somebody (usually a significant other) insists we get our ears checked. Unfortunately, this gradual process is not an inviolate rule. Sometimes traumatic hearing loss can occur with just a single significant incident.

What exactly is the “trauma” of a gunshot that may damage our hearing? Further, if a decibel is exactly equal to 0.1 bels, what's a bel anyway? The true working components of the ear are hidden away and buried in our skulls leaving their function as a near total mystery. What we want to do in this article is to provide technical information about how the ear is structured, how it works, and consequently, what can be done to protect this precious sense. We realize that most people are not biology majors. However most people are not physics majors either yet we hunters love to learn about bullets, terminal ballistics, recoil, foot pounds of energy, trajectories and the like. So class...sit up and pay attention.

The outside part of the ear is called the pinna. Its function is to round up waves of air pressure (sound) and focus them into our external ear canal as well as keep debris out of the canal. In many of our game animals, the pinna is mobile and aids in sound localization, but much less so in us. Stretched across the external ear canal about an inch or so from the outside is the eardrum. The eardrum is a thin membrane with a surface area of about 70mm that seals off the cavity of the middle ear from the external ear canal. Air pressure is equalized on both sides of the eardrum by the descent of the Eustachian tube that starts in the middle ear and goes into the posterior part of the nasal canal. A significant difference in pressure across the eardrum can be painful and distort hearing (popping ears at altitude or depth equalizes the pressure).

The eardrum is the place where the air pressure waves (sounds) are converted into mechanical vibrations. Our hearing, which really doesn’t rank near the top in the animal kingdom, is still quite amazing. At its most sensitive range (3000 Hz) the ear drum’s deflection when vibrating is remarkably subtle (0.000,000,01 centimeters). In order to transmit and amplify these subtle mechanical vibrations, three very small bones are linked from the eardrum to the organ which converts mechanical vibration into neurological impulses, the cochlea. Skipping the Latin, these bones, which are held together by firm ligaments, are known as the hammer, anvil, and stirrup. The hammer is connected to the eardrum and at the other side of this bony linkage is the stirrup’s footplate. This footplate acts as a piston generating mechanical waves at its attachment to the cochlea, the oval window.