Wind turbines are a source of clean renewable energy, but some people who live nearby describe the shadow flicker, the audible sounds and the subaudible sound pressure levels as "annoying." They claim this nuisance negatively impacts their quality of life.

A team of researchers from the University of Toronto and Ramboll, an engineering company funding the work, set out to investigate how residential distance from the wind turbines -- within a range of 600 meters (1,968.5 feet) to 10 kilometers (6.2 miles) -- affects people's health.

They reanalyzed data collected for the "Community Noise and Health Study" from May to September 2013 by Statistics Canada, the national statistical office. The team reports their new analysis in the Journal of the Acoustical Society of America.

"The Community Noise and Health Study generated data useful for studying the relationship between wind turbine exposures and human health -- including annoyance and sleep disturbances," said Rebecca Barry, an author on the paper. "Their original results examined modeled wind turbine noise based on a variety of factors -- source sound power, distance, topography and meteorology, among others."

The team's new assessment confirmed Statistics Canada's initial findings. "Respondents who live in areas with higher levels of modeled sound values (40 to 46 decibels) reported more annoyance than respondents in areas with lower levels of modeled sound values (<25 dB)," Barry said. Unsurprisingly, the survey's respondents who live closer to the turbines "were more likely to report being annoyed than respondents who live further away."

The earlier Statistics Canada study found no direct link between residents' distance from wind turbines and sleep disturbances (as measured by sleep assessments and the Pittsburgh Sleep Quality Index), blood pressure, or stress (either self-reported or measured via hair cortisol). However, the more recent study showed that survey respondents closer to wind turbines reported lower ratings for their environmental quality of life. Barry and her co-authors note that their cross-sectional study cannot distinguish whether these respondents were dissatisfied before the wind turbines were installed.

"Wind turbines might have been placed in locations where residents were already concerned about their environmental quality of life," said Sandra Sulsky, a researcher from Ramboll. "Also, as is the case with all surveys, the respondents who chose to participate may have viewpoints or experiences that differ from those who chose not to participate. Survey respondents may have participated precisely to express their dissatisfaction, while those who did not participate might not have concerns about the turbines."

The team's more recent study didn't explicitly find evidence that exposure to wind turbines actually impacts human health, but in the future, "measuring the population's perceptions and concerns before and after turbine installation may help to clarify what effects -- if any -- exposure to wind turbines may have on quality of life," Sulsky said.