Sonic Patterns I: The Noise - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 176

Fig. 6.17 Relationship between sound and primary and secondary health effects
indicated the physical effects of noise (noise-induced hearing loss, NIHL) and the
nonphysical effects. The cumulative effects of the different components of noise
parameters and life trait such as age, personality, mental functioning, time of day,
and noise sensitivity represent the moderating factors. Sleep disturbance and
annoyance are the mediators between physical factors and secondary health effects
(reduction of health quality, diseases). The noise-induced hearing loss acts directly
on the secondary health effects.
It is interesting to note that there is a strong correlation between noise and
annoyance, but the correlation is weak between noise sensitivity and noise level.
According to the World Health Organization (WHO), seven categories of
adverse health effects of noise have been recognized (Fig. 6.18 ):
Hearing impairment is the result of many causes such as trauma, ototoxic drugs,
infection, and heredity. Below 70 dB also prolonged exposure can produce
damage, but when the sound pressure is above 85 dB for more than 8 h the
risk of hearing damage increases.
Hearing loss is largely caused by exposure during work activity, and children
seem more sensitive to damage to hearing. Hearing impairment in some cases
is accompanied by loudness perception (loudness recruitment), distortion
(paracusis), and tinnitus. Hearing losses produce in the subjects, according to
age, different effects such as sense of isolation, depression, loneliness, impaired
speech discrimination, impaired school and job performance, and later limited
job opportunities.