Wind turbine acoustic investigation: Infrasound and low-frequency noise—A Case Study
Bulletin of Science, Technology & Society|Stephen E. Ambrose , Robert W. Rand , and Carmen M. E. Krogh|September 10, 2012
Abstract
Wind turbines produce sound that is capable of disturbing local residents and is reported to cause annoyance, sleep disturbance, and other health-related impacts. An acoustical study was conducted to investigate the presence of infrasonic and low-frequency noise emissions from wind turbines located in Falmouth, Massachusetts, USA. During the study, the investigating acousticians experienced adverse health effects consistent with those reported by some Falmouth residents. The authors conclude that wind turbine acoustic energy was found to be greater than or uniquely distinguishable from the ambient background levels and capable of exceeding human detection thresholds. The authors emphasize the need for epidemiological and laboratory research by health professionals and acousticians concerned with public health and well-being to develop effective and precautionary setback distances for industrial wind turbines that protect residents from wind turbine sound. A portiion of the report is provided below. Click the links on this page to access the full paper.
Abstract
Wind turbines produce sound that is capable of disturbing local residents and is reported to cause annoyance, sleep disturbance, and other health-related impacts. An acoustical study was conducted to investigate the presence of infrasonic and low-frequency noise emissions from wind turbines located in Falmouth, Massachusetts, USA. During the study, the investigating acousticians experienced adverse health effects consistent with those reported by some Falmouth residents. The authors conclude that wind turbine acoustic energy was found to be greater than or uniquely distinguishable from the ambient background levels and capable of exceeding human detection thresholds. The authors emphasize the need for epidemiological and laboratory research by health professionals and acousticians concerned with public health and well-being to develop effective and precautionary setback distances for industrial wind turbines that protect residents from wind turbine sound. A portiion of the report is provided below. Click the links on this page to access the full paper.
Introduction
Industrial wind turbines (IWTs) are being situated near human habitation in increasing numbers. In some communities individuals who are exposed to wind turbines report experiencing negative impacts including adverse health effects. Falmouth Massachusetts, USA is a community located in a quiet rural environment where there were reports of negative health effects from locating IWTs too close to residences. Some Falmouth residents have identified wind turbine noise as a cause of negative effects.
During a noise study investigating acousticians experienced adverse health symptoms similar to those described by residents living at the study location and near other IWT sites. The onset of adverse health effects was unexpected and persisted for some time after leaving the study area. This case study provides wind turbine noise measurements and other technical data and describes the symptoms experienced by the investigators and explores the plausibility that wind turbine low-frequency energy could contribute to reported adverse health effects.
Background - Falmouth, Massachusetts, U.S. Wind Turbines
Falmouth, Massachusetts recently installed three IWTs (Vestas, V82, 1.65 MW); two owned by the town located at the municipal wastewater treatment plant (WIND1 and WIND2) and one privately owned at a nearby industrial park (NOTUS). This area has a limited amount of daytime business activity and only a distant highway with low traffic volumes at night. The area is representative of a quiet rural environment with widely spaced houses. WIND1 and NOTUS are installed with the nearest residences approximately 400 m (1,300 feet) and 520 m (1,700 feet), respectively. The WIND1 and NOTUS IWTs were installed over several months, with WIND1 being the first to come on line in March 2010. A short time later, neighbors began to complain about excessive noise coming from WIND1. Later that year, NOTUS began operation and similar complaints came in from other neighbors. Complaints continued for months and neighbors were reporting that they could not adjust to the fluctuating sound, the endless swish and thumps. They found the noise to be intrusive and disruptive to normal at home activities. WIND2 was not operating during this study.
These fluctuating audible sounds or amplitude modulations are the routine characteristic of IWTs and can be disturbing and stressful to exposed individuals (G. Leventhall, 2006). During moderate wind speeds the IWT noise was clearly audible outdoors and for some, indoors. At times the noise included an audible low-frequency tone that came and went. Neighbors commented that the wind turbine noise was more noticeable indoors and it interfered with their relaxation and sleep.
The town responded to the numerous and persistent complaints by requiring postoperational noise surveys to determine if there were justifications for complaints. Neighbors responded by hiring legal counsel and had independent noise measurements performed and evaluated for adverse impacts. Most measurements were conducted by experienced acousticians. The primary acoustic quantifier measured was the average A-weighted sound level (dBA). The sound levels generally ranged from the mid-30s to mid-40s dBA. Some noise-level variations were due to differences for time of day, wind speed, and wind direction (upwind or downwind). Measured sound levels were fairly consistent from each survey provider. However, the acoustic reports had little effect on complaint resolution.
Falmouth Health Complaints
After WIND1 and NOTUS IWT started up, neighbor complaints included adverse health symptoms. They had days where they were unable to enjoy the previous peace and tranquility while at home, unable to relax, felt tense, and felt a strong desire to be someplace else. They noticed some relief when outdoors. The lessening of adverse effects when outdoors and the indoor worsening are consistent with the findings of low-frequency noise (LFN) effects exposure (Burt, 1996). Typically, the indoor A-weighted sound level is lower than the outdoor, especially when indoor human activity is at a minimum. The house exterior walls provide more middle- to high-frequency band attenuation than for the low and very low bands. Therefore, the average A-weighted sound level by itself may not be a useful measurement indicator for determining the potential for IWT complaints.
Some complainants described having significant difficulties living in their home with reports of experiencing headaches, ear pressure, dizziness, nausea, apprehension, confusion, mental fatigue, lassitude (inability to concentrate, lethargy). These were worse when IWTs were operating during moderate to strong winds. A few neighbors moved their bedrooms into the basement in an attempt to get a good night’s sleep. Others were forced to leave their home to sleep farther away at a family or friend’s house or even in a motel. These symptoms (DeGagne & Lapka, 2008; Schust, 2004) and behavior patterns (H. G. Leventhall, 2004) are consistent with LFN exposure suggesting that IWT lowfrequency energy may be a factor.
