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Acoustic trauma is the sustainment of an injury to the eardrum as a result of a very loud noise. Its scope usually covers loud noises with a short duration, such as an explosion, gunshot or a burst of loud shouting. Quieter sounds that are concentrated in a narrow frequency may also cause damage to specific frequency receptors. [1]
The U.S. Department of Defense has established criteria for equipment that produces impulse noise at levels above 140 dB peak SPL and requires hearing protection be worn to prevent damage human ears. [4] An impulse noise filter can enhance the quality of noisy signals to achieve robustness in pattern recognition and adaptive control systems.
By including a 2 dBA margin of safety which reduces the 8-hr exposure allowance to 80 dBA, the study estimated a hearing change of 2.1 dB or less in 99% of children. To preserve the hearing from birth until the age of 18 years, it was recommended that noise exposures be limited to 75 dBA over a 24-hour period. [45]
OSHA states that an employer must implement hearing conservation programs for employees if the noise level of the workplace is equal to or above 85 dB(A) for an averaged eight-hour time period. [57] OSHA also states that "exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level". [31]
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Boomerang, a gunfire locator, being used by British forces in Afghanistan Shooting Detector Diagram. A gunfire locator or gunshot detection system is a system that detects and conveys the location of gunfire or other weapon fire using acoustic, vibration, optical, or potentially other types of sensors, as well as a combination of such sensors.
The term "cumulative" EPNdB is the combination of the noise margins from the three ratings. It is defined as the sum of the individual margins (difference between certified noise level and noise limit) at takeoff lateral, takeoff flyover and approach. [4] It is important to make the distinction between loudness and noisiness.
The day-night average sound level (Ldn or DNL) is the average noise level over a 24-hour period. The noise level measurements between the hours of 22:00 and 07:00 are artificially increased by 10 dB before averaging. This noise is weighted to take into account the decrease in community background noise of 10 dB during this period.