Human Dimension of the Soundscape: From Individuals to Society - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 121

Fig. 5.6 Hormesis dose-response relationship (Reproduced with permission from Rylander 2006 )
this stress. This reaction is particularly evident when the stimulus is sudden and
unexpected. In this way, a gunshot also except for people such as policemen who
are used to this sound, causes a contractive reaction. This reaction is created to
escape, to defend oneself from possible danger, because a strong sound is the result
of great energy that is released (e.g., strong sounds are produced by landslides,
volcano eruptions, earthquakes, tempests, etc.).
The loss of concentration in reading or thinking is a common reaction after a
sudden sound.
To measure exposure to traffic, usually the noise dose is averaged over 24 h, and
this contrasts with the principle that the highest noise level and the noisiest event
are the proxies of human pathologies. It seems apparent that the annoyance
increases with the increase of noise peaks. When traffic barriers are erected we
do not always observe improvement in the annoyance reaction because the back-
ground noise is significantly reduced, but not the noise peaks, which persist
although sonic barriers are present. For example, when the traffic noise is continu-
ous this has less effect on the concentration of schoolchildren than sudden noises
such as those produced by aircraft. Peaks are more difficult to shield than continu-
ous sounds.
Noise pollution is increasing as urban growth spreads. The negative effect of
noise on health produces hearing impairment, reduction of speech communication,
cardiovascular risk, sleep disturbance, psychological and performance reduction
effects, and a subjective feeling of annoyance.
Cardiovascular risk and hearing loss are effects caused by high noise exposure in
the occupational field. Sleep disturbance provoked by high noise exposure have
many effects on human health. Subjective sensitivity, sex, age, health status, and
socioeconomic status are related conditions.
Subjective illness and chronic diseases are factors that make the difference in
noise effects; in fact, sound intolerance can occur in subjects who are under
working or health stress.