When 68 years old Mr. Joshi sits down to watch TV, everyone else leaves the room. This causes him much distress but his family cannot tolerate the extremely loud volume of sound that Mr. Joshi needs if he is to follow the TV programme.
Mrs. Gupta (55 years old) has stopped answering the telephone. She finds it increasingly difficult to understand what the caller is saying, which sometimes causes her acute embarrassment.
Mr. Mehta is only 45 years old, but over the last few years, he has to make a special effort to concentrate when someone speaks to him because otherwise, he tends to miss a few words here and there. His problem increases in certain situations. In an office meeting, for example, he becomes especially conscious about this trouble because of the noise all around which interferes with speech comprehension.
With increasing age, quite a few people experience a decline in their ability to hear. Continued exposure to loud sounds (as in a factory workshop, etc.), intake of some medicines (like certain antibiotics) or physical injury to the region around the ear can also cause hearing problems.
Generally however, it is just the process of growing old that makes it more and more difficult for the hearing nerve to carry the sound signals from the ear to the brain where sound is perceived and understood. The hearing nerve, also called the Acoustic, Auditory or the VIII (eighth) Cranial nerve, can be compared to an electric wire composed of many thin strands, with each strand transmitting a different sound frequency. In other words, while some nerve fibres transmit sounds of lower frequency, others are conduits for higher frequency sounds. Thus, the entire range of sound frequencies audible to human beings (20 Hz to 20,000 Hz) is covered.
Ageing typically affects the nerve fibres that transmit high frequency sounds such as ‘s’, ‘sh’, ‘z’, ‘ch’, etc. Low frequency sounds like ‘b’, ‘d’, “g”, etc. remain relatively unaffected.
The words in any language are combinations of various sounds put together. To a person suffering from hearing loss caused by ageing (called Presbyacusis), the question, "Should Shalini go to school on Saturday?" might sound like "**ould **alini go to **cool on *aturday?"
In the initial stages, when his hearing loss is not too severe, a person can correctly guess the meaning, with reference to the context in which the sentence has been spoken. He begins to pay conscious attention to the lip movements of the speaker thus getting some visual cues, which help him guess with somewhat greater accuracy. Such guesswork, however, is not always possible, like when talking on the phone, for example, he cannot see the listener.
As his problem progresses, these initial techniques become less and less effective. Along with the other limitations that increasing age usually brings along, his hearing problem makes verbal communication more and more tedious. He might begin to lose his confidence in conversational situations and gradually withdraws into a shell. He prefers to avoid meeting people, sometimes becoming a target of ridicule by even his well-meaning friends and relatives. He might find it difficult to enjoy watching television since the loud volume he requires for audibility might hurt the ears of the normally hearing listeners around him who might protest. His hearing loss automatically makes his own speech abnormally loud (he tends to shout since he cannot hear himself well either). Some chronic cases of ignored hearing loss are unclear or slurred in their speech because they cannot accurately monitor it. This is the person who should seek professional advice on the feasibility of acquiring a suitable hearing aid.
Hearing aids are to the ear what spectacles are to the eyes. Like eyeglasses, hearing aids do not change the basic nerve deafness problem (Presbyacusis is irreversible), but they enable the person to hear well. And just as eyeglasses cannot be purchased without proper testing, a hearing aid should also be fitted by a qualified audiologist who is trained to ascertain the type and degree of hearing impairment and advise on the model of hearing aid most suitable for an individual.
All hearing aids are basically amplifiers of environmental sounds; that is, they make all sounds louder and introduce them into the ear. Each hearing aid (whatever be its type or size) has a microphone that collects sounds, an amplifier that makes them louder and an earphone that takes these amplified sounds into the ear. The degree of loudness can be adjusted through a volume control. Like any other electronic equipment, a hearing aid needs a power-source, which is a battery-cell. There is also an on/off switch.
In addition to these common basics, sophisticated hearing aids include a variety of sound filters, which help in modifying sound quality to suit the individual's requirements based on his particular hearing loss. This makes the amplified sound less irritating and more bearable.
Hearing aids come in various sizes and models. The most common and least expensive are the body-worn or pocket type instruments which work on normal AA type of pencil cells but are more visible since a cord (or wire) extends from the receiving unit to the earphone.
There are two kinds of hearing aids: Behind-the-ear (BTE):
The BTE type has obvious cosmetic advantages over the pocket type since it is almost totally hidden behind the ear and covered by the hair. It also enables the person to receive the sound at the ear level since the microphone is near the ear, which helps in localising the source of sound. This is an important advantage compared with the pocket-type hearing aid, in which all sounds first go into the pocket (where the receiving unit is usually kept) and then into the ear through the earphone. For a person crossing a road, for example, it is important to know the direction of the car's horn. This is easily possible for the person wearing a BTE type of hearing aid. All BTE types require a small button cell (similar to the one used in watches). Such BTE hearing aids are usually imported from Europe and assembled in India under various brand names.
Inside-the-ear (ITE): These are worn inside the ear and require an even smaller battery cell. They are useful for certain types of hearing losses only.
Hearing-aid technology has come a long way from the time man first cupped his hand behind his ear to enhance his hearing capacity. The first hearing aids were mechanical cones, which were held near the speaker's mouth. When Alexander Graham Bell invented the telephone, the electrical hearing aid was born. But because battery cells were big and heavy, these first hearing aids were carted along in a wheelbarrow! The invention of the integrated circuit (IC) has changed all that. And millions of satisfied hearing-aid users have benefited from these developments.