The human hearing apparatus has evolved into an efficient mechanism for the reception of airborne sound. Its frequency response is tuned quite precisely to the sound of the human voice. Exposure to prolonged and excessive noise is known to damage and destroy the sensory hair cells in the inner ear causing a permanent and quite characteristic hearing loss. Other direct effects of noise on the human body have not been substantiated by experimental evidence. Physiological changes may occur but the effects of these on the body are not fully understood. Work performance may be degraded depending on the task and the character of the noise. Hearing loss from noise is an entirely preventable occupational disease.