PERCEPTION AND SIGNIFICANCE OF TRANSPORTATION NOISE CHANGES

The perception and significance of transport noise change have been central to the noise debate in the current Heathrow Terminal 5 Public Inquiry. 'Perception' relates to the ability of human hearing to detect a noise change, and 'significance' relates to effects of noise changes on humans, such as sleep disturbance, annoyance, and interference with speech. This paper reviews and interprets evidence given to the inquiry on noise changes, especially changes in aircraft and road traffic noise, in terms of the Laeq,16h and Laeq,18h noise indices, respectively. It considers the following questions: (1) the minimum perceptible change for 'simple' sounds; (2) how far perceptible change for 'simple' sounds applies to noise indices; (3) how important the nature of the change to the noise index is; and (4) how to assess the noise changes. The minimum perceptible change of noise seems to be about 3dB(A). Illustrative examples show that perceptible changes in Laeq,16h and Laeq,18h differ from that of a sound level, because of their inherent averaging processes. When assessing changes, it is important to consider changes in the noise's character as well as its time pattern. The human response to noise is complex, and there has been some criticism of the DMRB method of assessing changes in road traffic nuisance. For the covering abstract, see IRRD E100715.