Preferred Hearing Solutions

The normal human ear can distinguish between some 400,000 different sounds, some weak enough to cause the eardrum to move as little as one-tenth (1/10) the diameter of a hydrogen molecule. Perhaps you recall being aware of the persistent buzzing of a mosquito on a quiet summer afternoon, until a jet aircraft flew overhead and overpowered that quiet sound. Those are two sounds different in both loudness and character, that your sense of hearing can help you recognize and label. Let's investigate this by exploring what sound is and how your sense of hearing works.

When a telephone rings, it produces a series of disturbances in the surrounding air and these disturbances, or sound waves, travel out and away from the source (in this case, the telephone). Your hearing mechanism transforms and transmits these sound waves as a message to your brain. Your brain then interprets the message.

Before the message can get to your brain, however, it must pass through three well-defined sections of the ear. The outer ear, the middle ear, and the inner ear. The outer ear includes the pinna, the part of the ear we can see attached to the side of our head, plus the ear canal.  The pinna is built to help gather sound waves and funnel them down the ear canal to the eardrum. The sound waves then strike the eardrum, or tympanic membrane, which is about as thin as tissue paper but very strong. The eardrum is the dividing line between the outer and middle ear. The eardrum vibrates when the sound waves strike it.

Attached to the eardrum is a chain of three small bones called the ossicular chain. The bones are in the pea sized middle ear cavity. The ossicles are the smallest bones in the entire human body, and they are full size when we are born. The individual bones are smaller than a grain of rice, and they are named after objects which they resemble. The bone attached to the eardrum is the malleus (hammer), the second bone is the incus (anvil) and the third is the stapes (stirrup). As the sound wave moves the eardrum, it moves the ossicles. The three bones actually form a lever system that transfers the energy of the sound waves from the outer ear, through the middle ear and into the inner ear. The last bone in the ossicular chain, the stapes (stirrup), is attached to a tiny membrane called the oval window. The oval window is actually an entrance to the inner ear which contains the organ of hearing, or cochlea. When the stapes bone moves, the membrane in the oval window moves with it.

On the other side of the oval window is the fluid filled channel of the cochlea. This fluid is disturbed by movements of the membrane in the oval window. Inside the cochlea are thousands of microscopic hair cells (about 15,500) which are set in motion whenever the fluid is disturbed. Stimulation of the hair cells, in turn, causes electrical impulses to be sent to the brain.

The electrical impulses represent the fourth change in the sound's message from one form of energy to another: from the acoustical energy of the sound waves entering the ear, to the mechanical energy in the chain of bones, to hydraulic energy in the fluid of the cochlea, to the electrical energy of the impulses that travel to the brain. The brain then interprets the electrical energy as sounds.

To arrange a free hearing test, call Preferred Hearing Solutions at 951-652-9655, 951-303-8886 or request an appointment online