When 68 year 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 which Mr. Joshi needs if he is to follow the TV programme.
Mrs. Ranade (age: 55 years) 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 noises all around which interfere 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 strong medicines (some antibiotics) or physical injury to the region around the ear can also cause a hearing problem.
Generally however, it is just the process of growing old, which 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.
This hearing nerve (called the Stato-Acoustic or VIII Cranial) can be compared to an electric wire which is composed of many thin strands. But in the nerve, each strand transmits 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 which 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 (medically termed Presbyacusis), the question :
“Should Shalini go to school on saturday?” might sound like:
**alini go to