Investigation of environmental low-frequency noise

The paper describes the results of theoretical and experimental investigation of environmental low-frequency noise and vibration. The main aim of this investigation was to check up the popular belief that this noise is being generated by underground gas pipes. The theoretical hypothesis has been developed which shows that under certain circumstances underground gas pipes may be in fact one of the sources of low-frequency noise. According to this hypothesis, underground pipes are able to effectively generate Rayleigh surface waves in the ground. Then, propagating to the buildings, these waves can result in generating structure-borne noise in buildings. The 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 legal aspects of this problem deserve further consideration.