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1 dB = 1 / 20 ln 10 is the decibel. The commonly used reference sound exposure in air is [2] = . The proper notations for sound exposure level using this reference are L W/(400 μPa 2 ⋅s) or L W (re 400 μPa 2 ⋅s), but the notations dB SEL, dB(SEL), dBSEL, or dB SEL are very common, even if they are not accepted by the SI.
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]
High levels of such a noise (200+ decibels) may damage internal organs{{[1] [2] [3]}, while impulses exceeding 180 decibels begin to present a risk of rupturing the tympanic membrane if hearing protection is not worn. The U.S. Department of Defense has established criteria for equipment that produces impulse noise at levels above 140 dB peak ...
The ear can be exposed to short periods of sound in excess of 120 dB without permanent harm — albeit with discomfort and possibly pain — but long term exposure to sound levels over 85 dB(A) can cause permanent hearing loss. [31] There are two basic types of NIHL: NIHL caused by acoustic trauma; NIHL that gradually develops.
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.
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 ]
Shot noise or Poisson noise is a type of noise which can be modeled by a Poisson process. In electronics shot noise originates from the discrete nature of electric charge . Shot noise also occurs in photon counting in optical devices, where shot noise is associated with the particle nature of light.
The threshold of hearing is generally reported in reference to the RMS sound pressure of 20 micropascals, i.e. 0 dB SPL, corresponding to a sound intensity of 0.98 pW/m 2 at 1 atmosphere and 25 °C. [3] It is approximately the quietest sound a young human with undamaged hearing can detect at 1 kHz. [4]