Definition of Terms
ACOUSTIC TRAUMA - A single incident that produces an abrupt hearing loss. Blows to the head, and blast noise are examples of events capable of producing acoustic trauma.
ACTION LEVEL - The sound level which when reached or exceeded necessitates implementation of activities to reduce the risk of Noise Induced Hearing Loss. OSHA currently uses an 8-hour time weighted average of 85 dB as the criterion for implementing an effective hearing conservation program.
DECIBEL (dB) - The unit used to express the intensity of sound. The decibel was named after Alexander Graham Bell. The decibel scale is a logarithmic scale in which 0 dB approximates the threshold of hearing in the mid frequencies for young adults and in which the threshold of discomfort is between 85 and 95 dB SPL and the threshold for pain is between 120 and 140 dB SPL.
HEARING HANDICAP - A specified amount of permanent hearing loss usually averaged across several frequencies which negatively impacts employment and/or social activities. Handicap is often related to an impaired ability to communicate. The degree of handicap will also be related to whether the hearing loss is in one or both ears, and whether the better ear has normal or impaired hearing.
NOISE INDUCED HEARING LOSS (NIHL) - Develops over time or abruptly from exposure to hazardous levels of sound.
SOUND PRESSURE LEVEL (SPL) - A measure of the ratio of the pressure of a sound wave relative to a reference sound pressure.
