A Listening Test on the Effects of Normal and Other Amplitude Modulation of Wind Turbine Noise on Perceived Annoyance Using In Situ Recordings

Wind turbine noise (WTN) can be a source of annoyance and discomfort to individuals exposed to it. Previous work has investigated perceived annoyance due to the presence of normal amplitude modulation (NAM) and other amplitude modulation (OAM) using synthesised stimuli. This paper presents a listening test investigating the relationship between WTN annoyance and the amplitude modulation (AM) characteristics of the noise, utilising in situ recordings reproduced at their real-world sound pressure levels. A series of WTN recordings were taken and analysed for AM characteristics in accordance with IEC 61400-11 and IEC TS 61400-11-2. Using the AM metrics, these recordings were interpreted and identified as including NAM or OAM. A total of 23 test participants were presented with a selection of these recordings, and asked to rate them in terms of their annoyance and loudness, as well as offer their comments. An analysis of the results confirms that recordings containing OAM were rated as more annoying and louder than those containing NAM. Results suggest that modulation depth and A-weighted sound pressure levels are positively correlated to perceived annoyance. In contrast with previous study results, intermittence was indicated in comments to be a significant factor in rated annoyance.