Sound Reflection from a Motorway Barrier

Christopher Day

New Zealand Acoustics, 18(1), pp.15- 20 . (2005).

The erection of a noise barrier on one side of the southern motorway in South Auckland caused complaints from a number of residents on the ‘reflected’ side of the barrier with claims of significantly increased noise levels. A successful application to the Environment Court for orders to have the barrier removed, gave the opportunity to measure the difference in noise level with and without the barrier. Three measurement positions were used which were representative of the complainants. Noise levels at residences close to the motorway (30m) were consistent day to day and the difference with and without the barrier was less than 0.4 dBA. Noise levels at the more distant residences varied by up to 17 dBA due to traffic flow and meteorological effects. There was no measurable change in noise level (= 0.5 dB) at these outer positions following removal of the barrier. On the basis of these measurements, there does not appear to be any link between the residents’ reaction and the change (or lack thereof) in the noise environment.