Noise is an unwanted sound. Especially when very loud, it becomes a form of pollution because it is irritating, causes mental stress and may even lead to temporary or permanent deafness. The loudness (intensity) of sound is measured in decibels (dB). The scale goes from 0dB which is total silence to 200dB which would be measured next to a rocket taking off. Noise mainly comes from four sources: (a) aircraft noise, (b) road transport noise, (c) construction and industrial noise, and, (d) neighborhood noise. The problem generated by noise is not only that it is unwanted, but also that it negatively affects human health and well-being. In Hong Kong, noise generated in working areas is controlled by the Labour Department while noise generated in other places is controlled by the Environmental Protection Department.