Page 40 - Fall2019

“The New Secondhand Smoke”
Table 1. Specific noise levels affecting human health and function Sound Level
30 dB(A) [LAeq(8)]
55 dB daily average (Lden)
70 dB daily average [LAeq(24)] 70 dB(A) (LAmax)
85 dB(A) [LAeq(8)] 85 dB(A) [LAeq(1)]
Effect
Nonauditory health effects
Hearing loss
Interference with speech comprehension for those with normal hearing Occupational noise exposure (recommended limit)
Recommended exposure to prevent hearing loss
Source
WHO (Berglund, et al., 1999)
WHO, 2018
EPA, 1974 EPA, 1974
NIOSH, 1998
WHO (Berglund et al., 1999)
Sleep disruption
45 dB (Ldn) 45 dB (LAmax)
Disturbance of concentration and interference with learning
Sleep disruption
EPA, 1974; WHO (Berglund et al., 1999) WHO (Berglund et al., 1999)
60 dB(A) (LAmax)
Interference with speech comprehension for hearing impaired
Moulder (1993) for US Architectural and Transportation Barriers Compliance Board
WHO, World Health Organization; EPA, Environmental Protection Agency; NIOSH, National Institute for Occupational Safety and Health; LAeq(8), A-weighted equivalent continuous sound pressure level for 8 hours; Ldn, day-night weighted sound pressure level; Lden, day-night-evening- weighted sound pressure level; LAmax, maximum time-weighted and A-weighted sound pressure level; LAeq(24), A-weighted equivalent continuous sound pressure level for 24 hours; LAeq(1), A-weighted equivalent continuous sound pressure level for 1 hour. Definitions from WHO, 2018.
to 85 dB(A) [LAeq(1)] to prevent hearing loss (Berglund et al., 1999). The WHO report also discussed 55 dB(A) as the level at which adverse health effects of noise occur, and this noise level [55 dB day-night-evening-weighted sound pressure level
(Lden)] has been emphasized in later reports (WHO, 2018).
Specific Noise Levels
The nine specific noise levels affecting human health and function (Table 1) are discussed in order of increasing sound pressure levels, with emphasis on the disability rights aspects of ambient noise and safe noise exposure levels for the public. It is important to emphasize that in the United States, there are no federal guidelines, standards, or regulations for non- occupational or public noise exposure (Carroll et al., 2017).
Sound energy causes auditory damage and activates the stress responses to noise. The equal-energy hypothesis states that equal amounts of sound energy will produce equal amounts of hearing impairment and other effects, regardless of how the sound energy is distributed in time (Kryter, 1994; Berglund et al., 1999). The hypothesis may, however, underestimate the damage done by intermittent or impulse noise. In the United States, most noise levels affecting humans are measured in
A-weighted decibels because difficulty understanding speech is the material impairment from occupational noise exposure (NIOSH, 1998). Although A-weighted decibel measurements may be relevant for speech comprehension, the total sound pressure level is likely more important for human health.
Low-frequency noise [C-weighted decibels; dB(C)] may also impact humans, specifically causing damage to hair cells in the vestibular system responsible for balance (Stewart et al., 2016). An association between hearing loss and falls has been reported, with worse hearing being correlated with increased fall risk (Lin and Ferrucci, 2012). There are no published stan- dards for occupational or nonoccupational low-frequency noise exposure.
Thirty A-Weighted Decibel Noise Causes Sleep Disruption
Sound pressure levels as low as 30 dB(A) LAeq(8) and 45 dB LAmax can cause sleep disruption (Berglund et al., 1999). There are individual variations in sensitivity to sound during sleep and variations in sensitivity to sound during different phases of the sleep cycle. Even if the noise does not wake the sleeper, the sound causes electroencephalogram changes and also results in increases in heart rate (Buxton et al., 2012). Sleep
40 | Acoustics Today | Fall 2019