How We hear

In order to understand how we hear, we need to understand a little bit about both sound and the anatomy of the hearing mechanism.

Sound is the result of vibration. It is the movement of air particles, that are perceived in both frequency (pitch) and intensity (loudness). Frequency or pitch, is the number of cycles per second at which any sound is vibrating. Most sounds are complex, that is they are made up of a combination of many frequencies. The less a sound vibrates, (or less cycles per second) the lower pitch of the sound. For example, a train whistle or a buzz is a low frequency sound. The more a sound vibrates, the higher the pitch. For example, sirens or violins are high pitch sounds.

When we test hearing, we test a variety of sounds from low pitch to high pitch. We do this to determine how well each person hears each of these sounds. If a hearing loss is present, we can see from the audiogram, which sounds will be affected. This often determines the amount of difficulty one will have with understanding of speech. Vowels are primarily composed of low pitched sounds. If you place your hand on your throat and say the vowel sounds, you will feel the intensity of the sound. They are voiced. There is power and loudness when you say them. If you say consonant sounds, for example, p, b, t, s, k, and so forth, there is no intensity of sound. The consonants are unvoiced and therefore very soft.

Many people who lose their hearing, particularly through the aging process have better hearing in the low frequency range, and poorer hearing in the high frequency range. For that reason, often they can hear speech but are not be able to make out the words that have been said. They are hearing sound in a distorted way. They may hear the low frequency components, but because the high frequency portion is too soft or sometimes not heard at all, it is very difficult to differentiate one word from another. Hearing aids, particularly the newer, more advanced, digital and programmable hearing aids are especially effective for helping even people who could not wear hearing aids before, to use them very successfully.

The ear is divided into three parts:

The outer ear consists of the pinna (the part you can see), the ear canal, and the eardrum.

The middle ear is a small, hollow air filled cavity behind the eardrum The smallest bones of the body, the malleus, incus and stapes are located in this area. The malleus is attached to the eardrum . The incus connects the malleus to the stapes. The footplate of the stapes is imbedded in the oval window of the cochlea. They all work together in a chain to mechanically transmit sound.

The inner ear, or the cochlea, is a snail shaped structure that is filled with fluid and tiny hair cells. Their function is to send nerve impulses to the brain. Most people with hearing losses due to the aging process and many who have hearing losses for other reasons, have them because of damage to this area.

The balance mechanism (semicircular canals)is a structure that sits on top of the cochlea. It is responsible for letting you know what position you are in relationship to your surroundings. It is fluid filled and is very sensitive to changes in your orientation to the world. Occasionally a person who has a hearing loss, also has a problem with balance or dizziness. Testing is necessary to determine if this is related to the hearing loss or to another medical condition.

When the sound enters the ear, it makes the eardrum vibrate. Because the eardrum is attached to the grouping of middle ear bones, they in turn, vibrate. The last bone, the stapes, pushes into the oval window of the cochlea and because the fluid is disrupted by this, the tiny hair cells are stimulated and they send nerve impulses to the auditory nerve which then sends the sound to the brain. The outer hair cells respond to soft sounds while the inner hair cells are activated by more intense louder sounds. These responses send nerve impulses to the brain to the auditory cortex to allow you to process the sound.

When there is a problem with any one of the parts of the hearing mechanism, whether located in the outer, middle or inner ear, a hearing loss is present. It is essential that if you think you have a hearing loss, a comprehensive audiologic evaluation is performed by a certified, licensed audiologist. That way your hearing will be thoroughly evaluated to determine how much, and what type of loss is present.

If a hearing loss is located in the outer or middle part of the ear, a conductive hearing loss is present. Many conductive losses can be corrected by proper medical, otologic, or surgical intervention. Some of the reasons for a conductive loss may be simple, such as impacted cerumen (wax) in the ear canal, or be the result of infection, perforated eardrum(s) otosclerosis, recurrent ear infections or mastoiditis. The If you have a conductive hearing loss, or conductive component, you will be referred for additional medical consultation to determine if medical or surgical treatment is indicated. If it is not, you may be a candidate for hearing aid amplification.

A sensori-neural hearing loss is one in which the damage to your hearing mechanism has taken place in the cochlea or auditory nerve. Most nerves losses are cochlear in site. If a sensori-neural loss is present, and you wish assistance for you loss, we will be able to provide you with the very best hearing aid assistance possible. It is precisely this type of loss that benefits the most from newer advanced digital and programmable hearing aids.