The Transport Agency does not typically monitor noise at individual properties to address complaints, concerns or compliance.
This is particularly the case for houses located away from the road (i.e. greater than 50m to 100m from the road in urban areas and greater than 100m to 200m from the road in rural areas).
This is because in these locations, noise from the road may not be ‘dominant’. Dominant means noise levels are significantly above background (residual sound) levels. Background noise levels also include noise from wind and other weather, bird calls, human activities (e.g. talking, lawn mowing, use of a car, heat pump etc.) or noise from local roads.
In locations where the road noise is not dominant, it does not mean you will not be able to hear noise from the road. In fact, you might be able to hear noise from the road clearly - especially at night.
Noise monitoring measures the total noise at a location from all sources. When noise from background/ambient noise sources is dominant or similar to noise from the road it can be difficult to attribute noise to a specific source.
For example, if the background (residential sound level) noise level is 40 dB and the noise level from the road is 55 dB then the total noise level is 55.1 dB (the logarithmic sum of 40 and 55 dB). In this example, the road noise is dominant because the background noise has only a small influence on the total noise level and it is relatively easy to attribute the noise level to the road.
As the ‘road’ and ‘background’ noise levels get closer to each other, the influence of the background noise level on total noise level (background plus road) in decibels is greater. For example, if both the background and road noise levels are 40 dB the total noise level is 43 dB (the logarithmic sum of 40dB and 40dB). In this example, it is more difficult and unreliable to differentiate the contribution of noise from the road and from background.