The Character of the Local Environment
Dr Bob Thorne
Introduction
This Paper addresses the character of the environment for the Turitea wind farm hearing but the principles apply to all rural locations. The Manawatu ambient levels can be compared to the wind farm affected Waubra environment.
The character of the environment containing the development is assessed by describing the individual noises heard in the locality. Noise, for example, may be described as “truck noise”, “insect sounds”, and “breeze over grass sounds.” All these sounds have a different character and it is when that character changes that a noise 'stands-out' or becomes 'audible' within a locality.
The 'background' noise is that part that remains after the individual noises have ceased or temporarily moved; such as a passing car or bird call. The introduction of a major traffic route into a relatively quiet and peaceful semi-rural environment creates a significant change in the acoustic environment. Such sounds become audible because their characteristics are not 'masked' in any way by other sounds in the environment. In a city locality, for example, one car or a dozen extra cars will make hardly any difference to the overall acoustical character of the environment.
The environment within the district potentially affected by the wind farm can be readily described as having a rural nature, with the dominant sounds characterised by breeze over grassland, bird song and insects. In the rural environment of the wind farm development, the major addition of the industrial activity, the wind farm, will significantly change the acoustical character for the life of the wind farm(s). A sound that is not of the same character as the environment can be easily heard at levels below the nominal background level. This is because of the different tonal character between the noise sources. As a general guide, this type of noise is described as being 'intrusive' as the noise intrudes into the 'normal' environment.
Case Study
Four acoustical surveys at key residential locations on both sides of the ranges were undertaken using Larson Davis LxT Class 1 sound level meters. The A- weighted noise floor of the meter is 16 dB. A meter with a high noise floor (often 25 dB (A) or more ) is unable to record low background sound levels and thereby 'creates' incorrect background sound levels...
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