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10.6.17 Pure tone testing

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Pure tone testing is central to most auditory examinations, and is determined using an audiometer.

Patients are presented with pure tones at selected frequencies and loudness through headphones (air conduction) or a vibrator pressed against the mastoid portion of the temporal bone (bone conduction). The minimum level that a patient can hear is then determined for each frequency.

A graph, or audiogram, is drawn, showing the hearing loss at each frequency in decibels. It indicates the softest level that a person can hear at different levels, for intensity (loudness) and pitch (frequency).

Examples of results:

  • An audiogram showing 0 dB loss implies normal hearing.
  • A 30 dB loss means that conversation is faintly audible.
  • A 60 dB loss indicates that only a shout can be heard.

Tests are performed on calibrated instruments and must be undertaken in non-echo and sound proofed rooms. The patient must not be subjected to loud noises for at least 2 days before testing, as this may induce a false result.

Testing is done using frequencies of 500, 1000, 1500, 2000, 3000 and 4000 Hz.