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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.
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.
A noise or sound dose is the amount of sound a person is exposed to in a day. The dose is represented by a percentage. A noise dose of 100% means that a person has exceeded the permissible amount of noise. Any noise exposure after the 100% noise dose may damage hearing. The exchange rate is the rate at which exposure accumulates.
Noise damage is cumulative; all sources of damage must be considered to assess risk. In the US, 12.5% of children aged 6–19 years have permanent hearing damage from excessive noise exposure. [55] The World Health Organization estimates that half of those between 12 and 35 are at risk from using personal audio devices that are too loud. [11]
Noise-induced hearing loss is a permanent shift in pure-tone thresholds, resulting in sensorineural hearing loss. The severity of a threshold shift is dependent on duration and severity of noise exposure. Noise-induced threshold shifts are seen as a notch on an audiogram from 3000 to 6000 Hz, but most often at 4000 Hz. [16]
Hearing conservation programs [1] are programs that should reduce the risk of hearing loss due to hazardous noise exposure, if implemented correctly and with high quality. . Hearing conservation programs require knowledge about risk factors such as noise and ototoxicity, hearing, hearing loss, protective measures to prevent hearing loss at home, in school, at work, in the military and, and at ...
Various earmuff hearing protectors. Sound levels of some daily activities. A hearing protection device, also known as a HPD, is an ear protection device worn in or over the ears while exposed to hazardous noise and provide hearing protection to help prevent noise-induced hearing loss.
Noise from shipping and small boats is at the same frequency as sounds generated by marine organisms, and therefore acts as a disruptive element in the sound environment of coral reefs. [87] Both longer-term and acute effects have been documented on coral reefs organisms after exposure to noise pollution. [88]