Audiograms and Diagnosing Types of Hearing Loss
Ideally the audiogram would show a straight line, but in practice everyone is slightly different, and small variations are considered normal. Larger variations, especially below the norm, may indicate hearing impairment which occurs to some extent with increasing age, but may be exacerbated by prolonged exposure to fairly high noise levels such as by living close to an airport or busy road, work related exposure to high noise, or brief exposure to very high sound levels such as gunshot or music in either a loud band or clubs and pubs. Hearing impairment may also be the result of certain diseases such as CMV or Ménière's disease and these can be diagnosed from the shape of the audiogram.
Otosclerosis results in an audiogram with significant loss at all frequencies, often of around 40 dB(HL). A deficiency particularly around 2 kHz (termed a Carhart notch in the audiogram) is characteristic of either otosclerosis or a congenital ossicular anomaly.
Ménière's disease results in a severe loss at low frequencies.
Noise induced deafness or sensorineural loss results in loss at high frequencies, especially around 4 kHz and above, depending on the nature of the exposure to loud noise.
Typical examples of audiograms showing conductive, noise induced and age-related hearing loss can be found here.
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