Audiometry Principles

Audiometry is the measurement of hearing; it is often the determination of the threshold of hearing at a series of frequencies and perhaps for the two ears separately, though more detailed methods are also used. Audiometric tests are made for various reasons; the most common to determine the extent of hearing loss and for diagnosis to permit hearing aids to be prescribed.

In modern society a gradual loss in hearing is normal and occurs with increasing age; Figure 6.1.7 shows this condition. These curves show the average loss in a number of randomly selected men and women (not selected solely from noisy occupations), and these data are accepted as representing typical presbycusis conditions. (Presbycusis refers to the normal hearing loss of the elderly.) For all persons tested, the effect increases with age and is more pronounced at high frequencies than at low.

Men normally show the effect to a greater degree than women. In the last decade or so, women have experienced more presbycusis than formerly. Experts disagree as to whether noise is the predominant factor; but evidence shows that presbycusis and other processes of aging take place faster when noise levels and other social stresses are high. Another term, sociocusis, is being used to describe the hearing loss from exposure to the noises of modern society.

FIG. 6.1.6 Various degrees of injury to the hair cells.

Nerve Fibers Absent Severe Injury Total Degeneration

FIG. 6.1.6 Various degrees of injury to the hair cells.

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