Noise effects of the use of land-based wind energy : final report

Deliberations concerning the planning and approval of wind turbines often revolve around the issue of noise. A wide range of questions are raised that concern both noise generation and noise reduction as well as the impact of noise on the health and quality of life of the population. The present pub...
Ausführliche Beschreibung

Deliberations concerning the planning and approval of wind turbines often revolve around the issue of noise. A wide range of questions are raised that concern both noise generation and noise reduction as well as the impact of noise on the health and quality of life of the population. The present publication, ‘Noise effects of the use of land-based wind energy’, contains the results of a research project that investigated the impact of wind turbine noise. The focus of the research was on a particular sound characteristic of wind turbines known as ‘amplitude-modulated noise’. A frequently discussed thesis is that this particular sound characteristic, describable for example as a ‘whoosh’ sound, leads to increased awareness of noise and annoyance among residents. A key aim of the research was to investigate the frequency, duration and intensity of amplitude modulations caused by wind turbines, and to determine whether these are audible and measurable in the surrounding vicinity. Hence, in addition to measurements, the people who live in the vicinity of wind turbines were interviewed as well. The work to address this question was divided into five priority tasks: - Long-term sonic measurements in the emission and immission area over a period of at least two and up to six weeks, conducted in five study areas distributed throughout Germany. - Infrasound measurements in connection with amplitude modulation. - Analysis of the measurements using a method for the detection of amplitude modulation that was developed within the scope of this project. - Surveys of noise annoyance on the part of surrounding area residents in all five study areas. - Listening tests were also carried out in three of the study areas. The findings gleaned were as follows: - The median modulation depth on the immission side falls between 1.5 and 2.5 dB. - Only in one of the five study areas was it possible to identify a relationship of capacity dependency between the wind turbine and the frequency/modulation depth; this relationship was more pronounced in crosswind situations. Infrasound caused by wind turbines was detected in all of the study areas. The levels were always below the auditory threshold defined pursuant to DIN 45680 (Beuth 1997). In the listening test, the level of annoyance grew as the modulation depth increased. The results also showed that even the mere perceptibility of an amplitude modulation increases the level of annoyance reported by test subjects. On average, across all study areas and noise levels, participants in the annoyance survey found that the annoyance due to wind turbine noise was relatively low. Once the noise rating level at a residential building exceeds a value of approx. 35 dB(A), however, there is a sharp rise in the percentage of respondents who report that they feel annoyed or highly annoyed. Sound characteristics such as ‘whooshing’, ‘rushing’ and non-acoustic factors (attitude towards wind turbines and visual impact) are factors that have a considerable influence on the annoyance due to wind turbine noise. Self-reported noise annoyance correspond with the frequency of occurrence of identified, stable amplitude modulations. Ausführliche Beschreibung