The UK Institute of Acoustics Amplitude Modulation Working Group, of which Tom Levet was a member, developed a method for the quantification of amplitude modulation from wind turbines, to obtain a consistent and repeatable measure of modulation depth. This is now internationally acknowledged as best practice for the assessment of this acoustic feature and used as the basis of planning condition to regulate it's potential impact on annoyance. Its development and application to real wind turbine sites is described here.
The noise limits in ETSU-R-97 refer to the totality of wind farm noise affecting any residential location. This means that noise limits for individual sites have to take account of existing or other proposed development which can become quite complex and is discussed in this paper which Andy contributed to.
ETSU-R-97 is a document that has remained unchanged since it was first published nearly two decades ago, despite suffering from heavy criticism over those years. Andy McKenzie and Hoare Lea's Andrew Bullmore propose what an alternative procudure to the assessment and rating of wind farm noise in the UK might be, if ETSU-R-97 were to be superceded.
This paper gives some examples of a potential amplitude modulation (AM) assessment using the three metrics proposed in the IOA AM discussion document. Tom Levet presents results, discussing the analysis of noise measurements undertaken at a residential receptor location near a wind turbine site where operational and background noise periods were measured. Some of the issues involved are discussed. The objective of these metrics is a consistent quantification of the modulating character of the wind turbine related component of the noise, which can be implemented in a practical way.