The Development Of Appropriate Noise Scales For The Prediction Of Community Response To Urban Light Rail Systems

Higher than predicted levels of noise annoyance were reported by people living close to the Docklands Light Railway (DLR) following its opening in 1987. Analysis of the noise produced showed that in places the spectrum was dominated by high sound pressure levels in the 63 Hz octave band. The basis of the annoyance criteria applied by the DLR has been examined and the application of these criteria to the noise problems of New Urban Light Rail Systems has been questioned; particularly, the use of the A weighted Sound Pressure Level (dB(A)) to assess the impact of noise dominated by low frequency energy. Low frequency noise assessment by the dB(A) has been questioned from a theoretical perspective by examining the origins of the dB(A), and from a practical perspective by reviewing the relevant fieldwork. Sufficient doubt was thought to exist for further studies to be conducted. A series of subjective tests was proposed to assess the ability of the dB(A) to measure the relative annoyance of noises with differing frequency distributions. The available test methods were reviewed and ae set of experiments was designed, based upon the magnitude estimation method. A series of tests was conducted in which subjects were asked to estimate the annoyance of a number of sound stimuli. The dB(A) was found to correlate with the mean annoyance estimates only slightly less well than the Perceived Noisiness Level (PNdB), and significantly better than scales which give greater weight to low frequency noise. The tests are thought to be sufficiently accurate, unbiased and representative for broad conclusions to be drawn, but the relevance of the tests to the problem considered is questioned on the grounds that exposure to low frequency noise can have cumulative side effects.