Current levels of noise in an urban environment.

In 1961, the International Organization for Standardization prescribed upper tolerance limits for noise generated out-of-doors in residential districts. Between 1963 and 1970, vehicular traffic in the UK increased in volume by approximately 40%. This paper describes studies made throughout 1971 in which both peak and ambient noise-levels prevailing inside and outside buildings were measured. These levels were found greatly in excess of those regarded as tolerable ten years previously. Two methods for reducing noise-levels were considered. First, a barrier designed with the primary intention of reflecting rather than absorbing noise; secondly, a relatively simple form of double-glazing fitted to existing window frames. The barrier succeeded in reducing peak noise-levels but failed to influence ambients. The double-glazing attenuated both peak and ambient noise-levels significantly. Attention is drawn to the possibility of noise generated within buildings themselves becoming a source of discomfort for occupants and of annoyance to those outside. Noise-levels rising beyond 100 dB(A) were measured during evening business in the bar of a local hotel. A summary of data referring to noise-levels in the outdoor environment reveals that the upper tolerance limits prescribed by I S O are now being exceeded by 20 dB(A), or more, throughout 18 hours of the day. The findings are discussed in relation to the inevitable limits soon to be reached in adaptation of the human hearing mechanisms to increasing environment noise.