Groundbreaking infrasound study results unveiled

Engineer questions government wind turbine sound testing methods

By Barb McKay


An acoustics engineer is questioning the Ontario government’s methods for setting baseline sound limits for wind turbines after field testing was recently conducted in Kincardine.


Todd Busch, project manager for Swallow Acoustic Consultants Ltd., was in front of the Municipality of Kincardine council during its meeting last Wednesday to go over data from a study conducted within the boundaries of the Armow Wind Project last fall. Swallow was contracted by the municipality to study baseline acoustic and infrasound levels prior to the 92-turbine, 180-megawatt project becoming operational.


Engineers conducted interior and exterior sound testing at five homes within the project area between Oct. 30 and Nov. 14, 2015, using special microphones designed specifically to record infrasound (sound not picked up by the human ear). The sound measurements account for sound levels from wind in exterior testing.


Busch said when a noise impact study was conducted with audible sound testing for Armow Wind in 2013, engineers who did the study declared that the project would comply with Ontario Ministry of the Environment noise limits for industrial wind turbines. He said the study was done using an average wind speed at a particularly quiet site and a measurement of seven decibels was added to factor in sound levels at a higher wind speed. In the noise impact assessment summary, Busch said sound levels were calculated at between 37 and 39.8 decibels. The noise level limit set by the province is 40 decibels. Infrasound levels were not tested.


Busch said the report that was generated from the noise impact study did not explain why seven decibels was assumed for higher wind speeds and he questions the mehodology used to measure residual noise levels in the background environment. He does not believe the study factored in noise levels associated with wind and therefore is concerned the testing was compromised.


“We placed our microphones within 10 metres of where the noise impact assessment (study) microphones would have been,” Busch said. “A measurement of 39.8 decibels would be a candidate for scrutiny.”


Testing by Swallow generated acoustic sound levels of between 37 and 57 decibels outdoors and 20 to 40 decibels indoors. Infrasound levels measured between 57 and 88 decibels outdoors and 53 to 72 decibels indoors. He said the increase in sound from wind alone is staggering and should be explored further.


“We have been told many times from the provincial government that we can’t measure infrasound,” councillor Randy Roppel said. “Can you?”


“We did,” Busch replied.


Another concern is how the Armow Wind Project is classified - one of the main reasons the municipality wanted the sound testing completed. Armow is designated a Class 3 area by the province. That classification applies to agricultural areas, cottage and recreational resort areas, wilderness areas and small communities with populations less than 1,000 people and refers to areas that have mainly nature sounds and little to no road traffic.


The problem with lumping four areas into one class, Busch said, is that noises and sound levels that emulate from each of those areas vary greatly.


Swallow has recommended that the municipality move forward with further testing on the Armow Wind Project to study sound levels now that the wind turbines are operational. It also recommended that the municipality make a formal inquiry to the Ontario Ministry of the Environment and Climate Change (MOE) about how it conducted its testing and to reconsider how it classifies areas.


Councillor Laura Haight said she would like to see the municipality follow Swallow’s recommendation and communicate with the MOE prior to the next phase of study.


“There were attempts to clarify the MOE’s criteria (for sound levels) with the Enbridge project, but we were unsuccessful in getting responses,” mayor Anne Eadie said. “But we can try again.”


The municipality plans to proceed with the next phase of sound testing of the Armow Wind Project in 2017.


It is quite staggering the efforts that private citizens and municipal representatives have had to go to over the past 10 or so years to get the province to be accountable for this mess. In 2010 the Ministry of Environment hired HGC an acoustics firm via an RFP to report on infrasound/low frequency noise in wind turbine installations.
Here is a quote from that report:

“The audible sound from wind turbines, at the levels experienced at typical receptor distances in Ontario, is nonetheless expected to result in a non-trivial percentage of persons being highly annoyed. As with sounds from many sources, research has shown that annoyance associated with sound from wind turbines can be expected to contribute to stress related health impacts in some persons. Stress symptoms associated with noise annoyance, and in particular low frequency annoyance, include sleep interference, headaches, poor concentration, mood swings…”

HGC measured infrasound in private homes in Nova Scotia and here in Ontario and found problems. Why then did the gov’t of Ontario not do its due diligence and hire HGC (or another firm) to test complaint homes in wind projects instead of having them write a review on the subject? The ability to test has been available all along.


"the noise level limit set by the province is 40 decibels. Infrasound levels were not tested."

PS Unless things have changed, the audible noise level accepted by the MOE has been 40dBA but up to 51 dBA is allowed under increased wind conditions. The MOE should also be applying a 5dBA penalty for the whooshing, cyclical nature of the noise.
Moot points I suppose as you should not have to listen to the cyclical sound of turbines inside your home nor should anyone anywhere ever be subjected to 24/7 vibration and infrasound.


The article says "He said the increase in sound from wind alone is staggering and should be explored further."

You have to be very careful with windscreen design to control wind noise on the mic. An inadequate windscreen will give high low frequency levels. This has been known for a long time and is standard in old B&K literature. The recent interest in low frequency noise from wind turbines has led to development of new wind screens, which shouold be used for all outdoor LF measurements.

Of course, wind noise may mask wind turbine noise, which is why higher WT levels are permitted at high wind speeds.