Noise in relation to annoyance, performance, and mental health

There are many psychological factors which cause differences of human response to the same level of sound energy. Nevertheless, experiments have allowed these factors to be understood, at least to the extent where policy decisions can be made. The results show that increasing levels of noise increase annoyance, probably increasing the general arousal or excitability of the nervous system. This gives changes in performance which are sometimes detrimental, but not by any means always. Annoyance is associated with psychiatric ill-health, but increases in noise do not appear to increase the proportion of people with such illness.