In planning and developing new communities, conflicting requirements often arise. This is especially true for new residential developments near to existing high-noise sources, such as State Highways. In this situation “reverse sensitivity” effects may become a problem. This is where people begin complaining about a noise source which hasn’t changed for many years, because they have moved closer to the source.

The developers of a new subdivision in the North Island of New Zealand were concerned about potential reverse-sensitivity problems due to noise from a near-by State Highway. AES were engaged to design a traffic noise barrier which would provide sufficient traffic noise attenuation so as to minimise the need to acoustically upgrade dwellings in the subdivision, and to maximize the area of the subdivision in which the sound levels due to traffic complied with outdoor levels recommended by the World Health Organisation (WHO).

It was important at the beginning of this project to establish the expected noise levels within the subdivision without a traffic noise barrier in place. Knowledge of the traffic flow on the State Highway, and analytical prediction methods were used to simulate the propagation of noise from the road into the proposed subdivision, as shown in the figure opposite. From these results it could be seen that the noise levels outside the majority houses would exceed the maximum levels recommended by the WHO, and the levels inside many houses near the road would also be excessive.

A traffic noise barrier was designed, and its effectiveness simulated, as shown in the figure below. From these results it was seen that in over half of the subdivision the outside noise levels would be not exceed those recommended by the WHO, and the levels inside all houses would be acceptable, without any special acoustic treatment to the houses.

As a result of this work, individual home owners would not have to pay for expensive specialist acoustic treatment to their houses, and many in the subdivision would no longer experience any adverse effects due to the noise from the State Highway.