|Fact sheet No 258: Occupational and Community Noise - February 2001 (WHO, 2001, 5 p.)|
At birth the inner ear is fully developed and has its full complement of hair cells, supporting cells and nerve fibres. Unlike most other tissues in the body, mammalian hair cells and nerve fibres do not regenerate when damaged. (ref. Pathophysiology of the Ear p. 40)
The response of the human ear to sound depends both on the sound frequency (measured in Hertz, Hz) and the sound pressure, measured in decibels (dB). A normal ear in a healthy young person can detect sounds with frequencies from 20 Hz to 20 000 Hz. (Ref. Guidelines p. IX). Speech frequency ranges from 100 to 6000 Hz. (ref Guidelines p.XI).