Type and Degree of Hearing Loss

A conductive type of hearing impairment occurs when sound is not conducted efficiently through the ear canal, ear drum, or tiny bones of the middle ear. Conductive losses reduce the loudness of sound that is heard. A conductive impairment may result from blockage of the external ear canal, from a perforation (hole) in the ear drum membrane, from middle ear infection or from disease any of the three middle ear bones. This type of hearing impairment is usually correctable.

A person with a conductive hearing loss may notice that his ears may seem to be full or plugged. Crunchy foods, such as celery, sound very loud and he may have to stop chewing to be able to hear what is being said. With this type of impairment one hears quite well over the telephone.

Fortunately, the patient with a conductive hearing impairment will never go deaf. He will always be able to hear, with reconstructive ear surgery or by use of a properly fitted hearing aid.

A sensorineural hearing impairment may result from disturbance of inner ear circulation, increased inner fluid pressure or from disturbances of nerve transmission. The most common cause of sensorineural impairment is an aging change in the nerve endings (hair cells in the cochlea). This type of impairment is not able to be corrected by surgery, but rarely leads to deafness.

The person with a sensorineural impairment may state that he can hear people talking, but he cannot understand what they are saying.  An increase in the loudness of speech may only add to his confusion. Speech is audible, but not often understandable. He usually hears better in quiet places and he may have difficulty understanding what is being said over the telephone. He will probably hear low tones better than high tones and, therefore, may find a man’s voice more understandable than a woman’s higher pitched voice. Often the patient with this type of hearing impairment may not hear a doorbell or the telephone ringing in another room.

A central type of hearing impairment occurs when auditory centers of the brain are affected by injury, disease, tumor, heredity, or unknown causes. Loudness of sound is not affected necessarily, but understanding speech is.

A hearing impairment that is confined to one ear prevents a person from distinguishing the direction of sound. He will also have difficulty hearing from the involved side and may find it difficult to understand words in a noisy background or where the acoustics are poor.

When this impairment is secondary to a middle ear problem (i.e. conductive), surgery will usually be possible to restore the hearing, giving a better auditory balance. When the impairment is sensorineural (i.e. hair cell loss), it is often possible to restore some of this hearing balance with a hearing aid.