Backgrounder: Low Frequency Sound and Infrasound Report

In 2010, the Ministry of the Environment commissioned a study to review the latest science on low frequency noise and infrasound associated with wind turbines, and make recommendations.

The report's findings are based on best available science and have been validated by three experts in the field. The aim of the study was to answer some key questions about low frequency noise and infrasound from Ontario's wind turbines, including:

• What kind of noise do wind turbines produce?
• Is wind turbine noise harmful?
• Are Ontario's rules to control wind turbine noise stringent enough?

What kind of noise do wind turbines produce?Wind turbines produce sound over a wide range of frequencies including the entire audible range of human hearing, low frequency sound, and infrasound.

Is wind turbine sound harmful?
The best available science shows there is no direct health risk from wind turbine noise.

Are Ontario's rules to control wind turbine sound stringent enough?
In Ontario, wind turbines must be set back from people's homes by at least 550 metres. At this distance, much of the sound they produce lies outside the range that people can hear. This aligns with setbacks recommended by the World Health Organization.

The independent study confirmed that the ministry's rules to control wind turbine noise are appropriate.

The report's recommendations
The study made four recommendations.

1. Ontario should continue with its current approach used for:

• Assessing potential sound impacts prior to approving new wind turbines
• Evaluating compliance from wind turbines
• Adjusting limits downward for cases with strong mechanical tones.

2. The ministry should continue to monitor the emerging science and any changes to regulatory policies in other jurisdictions.

• Ontario will continue to follow science and government regulations as they evolve around the world.
• Through an arms length agreement with the Ontario Council of Universities, the province is funding ongoing study of renewable energy technologies and health.

3. The ministry should consider putting a new protocol in place to provide guidance to address complaints about indoor noise.  Complaints of low frequency noise most often relate to indoor sound where a number of factors make it difficult to measure this noise.

• Ontario is currently developing approaches to address complaints related to indoor low frequency sound in specific situations.  As recommended in the expert report, this will not replace the ministry's current compliance guidelines designed to assess sound outdoors.

4. The ministry should consider putting in place a proven way to measure noise at infrasonic frequencies.

• Ontario will continue to monitor scientific developments in the area of infrasound from wind turbines.  Ontario will seek a proven measurement procedure that can be used to quantify noise at infrasonic frequencies to aid in investigation of complaints and public concerns, as recommended by the report.

About the study
Howe Gastmeier Chapnik Limited (HGC), a consulting firm with an expertise in noise, vibration and acoustics, reviewed the latest science and government regulations for wind turbines.

HGC looked at more than 100 papers and reports. They also studied guidelines or regulations from Ontario, Alberta, Canada and other countries around the world. It gathered its findings in a report called Low Frequency Noise and Infrasound Associated With Wind Turbine Generator Systems. For a full copy of the report, or for other related scientific research, visit: www.ontario.ca/energyapprovals.