Abstract
Environmental sound exerts its effect upon those structures that are vibrated mechanically, and essentially, the damage that occurs as the result of vibrations of excessive amplitude depends upon the characteristics of the impinging sound and upon the condition of the aural structures. A blast May damage the middle-ear structures. The long-term steady, loud sounds more often encountered are more subtle in their effect and produce changes in the inner-ear structures. The process is purely a mechanical one and appears to have several stages, the extent of which depends considerably upon the state of the human organism at the time of insult.