Environmental low-frequency noise: what is it and how loud is it?

The aim of this paper is to describe the results of theoretical and experimental investigation of environmental low-frequency noise and vibration. The main objective of this investigation was to check up the popular belief that this noise is being generated by underground gas pipes. Theoretical hypothesis has been developed which shows that under certain circumstances underground gas pipes may be one ofthe sources of low-frequency noise. Experimental investigations of the low-frequency noise and vibration were carried out in several locations over the East Midlands (UK) and included high resolution measurements of noise and vibration spectra. Records were taken inside and outside the houses, as well as near buried gas distribution lines. In 50% of cases the low frequency noise complained of has been detected. However, the presence of ground vibrations was not observed in any location. Thus, at least during this series of experiments, there was no evidence of underground gas pipes being a source of low frequency noise. The measured characteristics of the air-borne noise show that as a rule its level is below the average threshold of human sensitivity. Thus, only exceptionally sensitive people can be affected. Nevertheless, even though a number of people sensitive to low-frequency noise is relatively small, the technical and tegal aspects of this problem deserve further consideration.