Overview / Cochlea / Auditory pathway / Audiograms
Scientific concept: Jérôme Ruel, Jean-Luc Puel, Nuno Trigueiros Cunha
Drawings: S. Blatrix, P. Minary

Clinical audiograms
To identify any hearing loss, clinicians produce audiograms by presenting different frequencies of pure tones at different intensities, using headphones.

"Normal" thresholds for each tested frequency are represented by the 0 dB straight line across the top.

Typical audiograms for "normally hearing" subjects are shown at different stages of life: thresholds, especially for high and mid-frequencies are almost always elevated with increase in age.

See also "presbycusis".


Speech audiograms

This test is based upon the ability of the subject to correctly repeat words which are presented to him at different intensities (without being able to lipread). A subject with normal hearing is able to repeat 100% of words correctly when presented at 20 dB (blue curve). A subject with a damaged cochlea, eg with a severe loss of outer hair cells (red curve), needs 50 dB amplification to begin to understand the words, but he will never get 100% correct responses however loud the sound intensity, because he is unable to discriminate the sounds clearly enough.
See also "hair cell pathology".


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