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July 9. 2010

Ansar GafurAIM SOP Phase I LP105 Commerce Valley West. Suite 410Markham. ONL3T 7W3

Re: Proposed Short-Duration Infrasound Measurement Protocol,Cultus, Clear Creek, and Frogmore Wind Farms

Dear Mr. Gafur.

HOC Engineering has been retained by AIM SOP Phase I LP (AIM) to conduct a measurement ofnoise at infrasonic frequencies at a group of residences located within the Cultus. Clear Creek, andFrogmore Wind Farms operated by AIM. Four residences have been identified as measurementlocations. This letter is intended as a summary of the work we are proposing to undertake.

Acoustic MeasurementsEnvironmental infrasound is an inherently difficult phenomenon to quantify, and the Ministry ofEnvironment does not have a protocol for its measurement or assessment. One of the chiefdifficulties is the fact that wind tends to be registered as infrasound by acoustic instrumentation,and conventional microphone windscreens offer little benefit at the relevant frequencies. Thus, ona windy day. if attempts to minimize this problem are not made, then the influence of the wind onthe measurement system may entirely mask the infrasonic noise of area wind turbines; the samesound levels might be measured regardless of weather the turbines were operating.

Our intention is to utilize a variety of measurement techniques to minimize this problem. The firsttechnique is simply to conduct measurements indoors, where the direct influence of wind isremoved. The second technique involves making measurements both with the wind farm inoperation, and then repeating the measurements with the wind farm shut down. The thirdtechnique is intended for use outdoors, and involves placing a microphone in a box located in ahole in the ground, covered with a material which is acoustically transparent at the frequencies ofinterest. Aspects of this in-ground technique are described in a number of places in the literature[1.2.3].

AIM SOP Phase I LP Page 2Proposed Short-Duration Infrasound Measurement Protocol July 9, 2010

Indoor measurements will be conducted in each residence. Both narrowband spectralmeasurements and 1/3 octave measurements will be conducted. Measurements will be conductedwith the wind farm in full operation, and then repeated with the relevant turbines stopped. Fastexperience indicates that the comparison of the two sets of measurements will show a reduction ininfrasound levels when the farm is shut off, thus showing the infrasound level attributable to theoperation of the nearby turbines, and the level attributable to natural phenomena. Measurementswill make use of procedures used in Denmark, as described in [4]. Including the time required tostop the wind turbines, we estimate that we will be in each residence for a period of 3 hours, butmany factors may influence the required time. Because of this, and the time for the installation ofthe outdoor equipment (see below), it will be necessary to visit two of the four residences on oneday. and two on the next day.

The in-ground outdoor measurement system will be deployed before any of the indoormeasurements are begun, at a single fixed installation location central to the residences.Instrumentation at this location \\ill be configured to log spectral sound levels in 1,3 octave bandsat regular intervals, and will thus measure sound with the plant cycling on and off several times.

Temporal Variation and Selection of Measurement PeriodIt should be understood that the acoustic emission of a wind turbine varies significantly with avariety of meteorological factors. Thus, a single visit to each house will be unlikely to capture theworst case condition. Two things will be done to help result in measurements being made under atleast reasonable conditions.

First, efforts will be made to select a measurement period which is appropriate. After initialcontact between AIM and each resident. HOC Engineering will make a preliminary call to eachresident to discuss availability, any specific concerns regarding weather, or a particular locationwithin the home where the infrasound issue appears most problematic. Following this call \\e wil lmake a preliminary selection of a measurement period based on the long range forecast,attempting to select a period where windy conditions are called for. We will inform the residentsof the provisional plan. On the morning of the appointed day. we will again check the forecast,and if possible contact the wind farm to ensure that the system, and in particular the turbinesclosest to the residences, is operating, or is predicted to be operating, at a high production rate,(wind conditions are not too light nor too strong). If the weather forecast looks poor, we willbegin rescheduling the visit, and notify the residents accordingly.

Second, the in-ground microphone system will remain in place for a period of at least one week,and will be measuring sound throughout the period. This will increase the likelihood of capturingdata during representative conditions.

Nonetheless, if in the event the weather conditions are not reasonable, it may be necessary torepeat the work.

Meteorological DataThe noise produced by wind turbines is a function of various meteorological conditions asindicated above. Thus it is important to record the meteorological conditions at the time of the

AIM SOP Phase I LP Page 3Proposed Short-Duration Infrasound Measurement Protocol July 9, 2010

measurements. In order to facilitate this, we intend to install a ground-level weather station at thefixed infrasound monitor location, which will log the weather conditions in regular intervals forthe duration of the measurements at that location. In addition to this, the wind speed recorded bythe turbine control systems themselves will be requested from AIM for each of the nearestturbines, and a second temporary weather station will be deployed at each residence for theduration of the measurements there.

Criteria and AssessmentThere are no Canadian standards, or uniformly accepted international standards, for themeasurement or assessment of environmental infrasound. However, useful criteria do exist. Weintend to compare the measured data with, at minimum, the threshold of hearing data described invarious papers [5, 6, 7, 8. 9], the reference threshold of hearing data described in ISO standard389-7 [10] and the Danish guidelines on environmental infrasound. as described by Jakobsen ofthe Danish Environmental Protection Agency [4]. which uses the G-weighting scheme defined byISO standard 7196 [11].

Microphonesintended for use with high-quality acoustic instrumentation which is designated as Type 1instrumentation by ANSI standard SI.4-1983 and IEC 60651. The model 2570 microphones havegood low-frequency performance, and are used for measurements of infrasound from varioussources of environmental infrasound such as waterfalls [12] and volcanoes [13].

Documentation and ReportingFollowing the work, the measurements made in each residence will be described, including themeasured sound levels, the time of measurement, the wind speed and direction prevalent at thetime of measurements, the measurement methodology, etc. This information will be assembled ina written report, which will be submitted to our client, AIM

We trust that this summary provides a useful outline of the work we intend to undertake, butplease call if you have any additional questions or concerns.

Yours truly.Howe Gastmeier Chapnik Limited

owe. MEn§, MBA. PEng Nick/McC'aHeTPEng

AIM SOP Phase I LP Page 4Proposed Short-Duration Infrasound Measurement Protocol July 9, 2010

[I] Jakobsen, J.. "Infrasound emission from wind turbines", Journal of Low Frequency Noise.Vibration and Active Control, vol. 24, no. 3, pp. 145-155. 2005.

[2] Shams. Q.A.. Zuckerwar. A.J. & Sealey. B.S., "Compact nonporous windscreen for infrasonicmeasurements". Journal of the Acoustical Society of America, vol. 118. no. 3. pp. 1335-1340.2005.

[3] Shams. Q.A.. Burkett. C.G.. Comeaux. T.. "Sub-Surface windscreen for the measurement ofoutdoor infrasound". presented at the 156th Meeting of the Acoustical Society of America. Miami.FL. 2008.

[4] Jakobsen. J. "Danish guidelines on environmental low frequency noise, infrasound andvibration". Noise Notes, vol. 2. no. 2. pp. 10-18. 2003.

[5] Watanabe, T. and M011er. H., "Low frequency hearing thresholds in pressure field and in freefield". Journal of Low Frequency Noise and Vibration, vol. 9. no. 3. pp. 106-115. 1991.

[6J Meller. H., Andresen. J.. "Loudness of Pure Tones at Sow and infrasonic frequencies". Journalof Low Frequency Noise and Vibration, vol. 3. no. 2. pp. 78-87, 1984.

[7] Watanabe, T.. "Simultaneous masking and temporal masking of low frequency sound".presented at the 13th International Conference on Low Frequency Noise and Vibration and itsControl. Tokyo Japan, 2008.

[8] Yeowart. N.S. and Evans. M.J., "Thresholds of audibility for very low frequency pure tones".Journal of the Acoustical Society of America, vol. 55. no. 4. pp. 814-818, 1974.

[9] Kurakata. K., Mizunanii. T.. Sato. H. and Inukai. Y.. "Effect of ageing on hearing thresholds inthe low frequency region". Journal of Low frequency Noise. Vibration and Active Control, vol.27. no. 3. pp. 175-184.2008.

[10] ISO 389-7:2005. "Acoustics - Reference zero for the calibration of audiometric equipment -Part 7.'Reference threshold of hearing under free-field and diffuse-field listening conditions".2005.

[ I I ] ISO 7196:1995, "Acoustics - frequency weighting characteristic for infrasoundmeasurements". 1995.

[12] Johnson. J.B., "Waterfall Infrasound", InfraMatics. no. 13. pp. 1-10, 2006.

[13] Johnson. J.B.. Lees. J.M., Yepes, H., "Volcanic eruptions, lighting, and a waterfall.differentiating the menagerie of infrasound in the Ecuadorian jungle". Geophysical ResearchLetters, vol. 33. L0630872006.