How does the ear work? When sound waves enter the outer ear, the vibrations impact the ear drum and are transmitted to the middle and inner ear. In the middle ear three small bones called the malleus (or hammer), the incus (or anvil), and the stapes (or stirrup) amplify and transmit the vibrations generated by the sound to the inner ear. The inner ear contains a snail-like structure called the cochlea which is filled with fluid and lined with cells with very fine hairs. These microscopic hairs move with the vibrations and convert the sound waves into nerve impulses - the result is the sound we hear. Exposure to loud noise can destroy these hair cells and cause hearing loss! A wide variety of noise sources may exist in the workplace. The NIOSH Noise Meter provides examples of some common sources and their expected noise levels. A more detailed explanation of common terms, good program elements, and implementation steps can be found in NIOSH Document: Preventing Occupational Hearing Loss - A Practical Guide, Publication No. 96-110, (1996, October). See more from topic source: https://www.osha.gov/html/a-z-index.html