Noise is unwanted or undesired sound, and can be said to be one of the most pervasive forms of pollution. It may be a potential problem at all times and places. Noise pollution is directly correlated to human activities (and in this respect is deemed to be increasing), and is mostly associated with urban areas. Noise pollution lowers the quality of life, and may lead to noise-related illnesses, both physical (the ear), and psychological. Noise pollution needs to be reduced to acceptable levels.
Noise has become a concern for increasing numbers of national authorities during the past decade. The main sources of acoustic nuisances are road, rail and air transport, recreational activities and industry, but people also complain more about noise from their neighbours.
A considerable number of people are exposed to levels of traffic noise that cause not only serious annoyance and sleep loss but also communication problems, and even learning problems in children. There is emerging evidence of an association between hypertension and ischaemic heart diseases and high levels of noise. Ambient noise levels continue to grow due to ever-increasing volumes of traffic.
This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities.
Noise legislation has been passed in various countries to regulate vehicle, aeroplane, and industrial noise. Typically, the noise threshold is around 55 decibels (dB), and the irritation threshold is 65 dB. Switzerland spends the most on acoustic problems in buildings in Europe.