Audiologists warn that all this exposure to sound comes with certain risks. Consider the home owner who wears his personal stereo while mowing his lawn. A typical lawnmower produces 85-90 dB of noise, enough to exceed the OSHA specified level of safe sound. After 30 minutes, the homeowner is placing himself at great risk for hearing loss. While one or even five such exposures is not likely to cause a permanent change in hearing, repeated exposures over the course of a few years will definitely damage hearing.
Toxic noise can deal a blow to the snail-shaped inner ear called the cochlea in two ways.
Acoustic trauma can result from a single strike typical of a high-powered pistol or rifle, permanently damaging tissue immediately. Far more common is noise-induced hearing loss, a cumulative process that occurs as excessive sound blasts away the ears and 20,000 to 30,000 sensory receptors known as hair cells. Hearing works when mechanical vibrations of sound are relayed by the bones in the middle ear to the rows of microscopic cilia on the hair cells and surface. These vibrations are instantaneously converted to electrical signals for delivery by the nerve fibers to the brain. Initially, excessive sound typically causes only temporary distortion of the hair cells, and the hearing deficit doesn t last.