Multiple wind turbine noise level measurement 

[To Victor Low, ENE]
Sent: June 29, 2009
Subject: RE: Multiple wind turbine noise level measurement

… In short, the most pressing and immediate issue is that Certificates of Approval (Air) have been issued for wind turbines with noise emission compliance limits specified in the approval. MOE [Ontario Ministry of the Environment] currently has no approved methodology for field measurement of the noise emissions from multiple noise sources. As such there is no way for MOE Field Staff, (and I would submit anyone else), to confirm compliance or lack thereof with the noise limits set in the approvals. …

A slightly more in depth response to your questions follows:

Step Up Transformer Station Issues

The first set of complaints relate to the operation of the step up transformer substation located to the south and something like 6 km away from the main part of the wind farm. These complaints are also divided Into two main types.

The first subset of transformer complaints run as follows:

The complainants state, and GDO [Guelph District Office of the MOE] Staff have confirmed, that the noise emissions from the transformers, (primarily at night), are considerably above the normal nighttime ambient noise levels previously encountered in that area (GDO Staff measurements utilizing the NPC-103 methodology, confirm that when the transformers are not operating, the normal nighttime background ambient noise level varies between 27 and 29 dBA. When the step up transformers are operating, the noise levels in the area vary between 37 and 39 dBA, [i.e. 32 dBA + 5 dBA tonal penalty to 34 dBA + 5 dBA tonal penalty], which is effectively a 10 dB increase over the usual nighttime levels that area residents have been conditioned to prior to March of 2006).

The second subset of transformer complaints run as follows:

The complainants state, and consultants retained by ——— as well as observations made by GDO Staff, confirm that there is a strong tonal component to the noise emissions from the operation of the step up transformers, (an audible tone at 300 Hz and another one at 360 Hz that run between 35 dB and 40 dB), which the complainants have identified as being particularly annoying and is probably the primary causative agent for the sleep deprivation that the three closest families are complaining of.

In both of the cases above, (or for that matter both of the above in combination), the noise emissions from the step up transformers are in compliance with NPC-232. The weighting against tones that occur below 500 Hz by the A scale system cancels out the audible tones occurring at 300 Hz and 360 Hz when viewed in conjunction with the remainder of the noise emissions from the transformer. As such the noise emissions from the transformers are in compliance with the CofA(Air) for the transformers, (40 dBA), and as MOE policy is to evaluate material discomfort/loss of use of property issues against the standards m NPC-232 and NPC-205, (in this case this is a Class 3 area as per NPC-232), and as there is no exceedance of the standards set out in those documents, there is considered to be no EPA S. 14(1) contraventions.

Understandably the complainants in this particular circumstance are not particularly receptive to our comments that the noise emissions from the transformer station are In compliance with the CofA(Air) requirements, and that MOE has no grounds to proceed with any abatement/enforcement action. Two of the three closest complainants to the transformer substation have moved out of their homes, (along with their families), and one of those families also have bought civil action against ——— (for nuisance).

Wind Turbine Issues

The second set of complaints relate to the operation of the 133 ——— wind turbines located in the Townships of Amaranth and Melancthon in Dufferin County. The 1.5 MW turbines, (total nameplate capacity of 199.5 MW), are spread out over an area of something like 180 km². These complaints can be divided into three main types.

The first subset of wind turbine complaints run as follows:

Complainants state, and consultants retained by ——— as well as observations made by GDO Staff have confirmed, that some of the wind turbines, when operating, are generating an audible low frequency tonal hum that is generally inaudible outside of structures, but is audible, again under certain conditions, inside the structures, (such as homes). Work done by the consultants has documented that certain of the wind turbines, (apparently all those built in the second phase of construction), (88 turbines), emit an audible tone, (a 35 dB hum” at the complainants residence when measured utilizing the NPC-l03 methodology), at 160 Hz. The “hum” is indeed generally inaudible outside of homes etc. but is audible inside homes etc. and is quite annoying to the occupants. It appears that the audibility inside the homes is dependent on the proximity of the turbine(s) to the homes, as well as the susceptibility of the home(s) to sympathetic vibration due to the low frequency “hum”. The complainants have identified the “hum” as being particularly annoying and is probably the primary causative agent for the sleep deprivation that the most vocal family was complaining of.

——— has indicated that they have identified the source of the 160 Hz “hum” as being in the gear train of the turbines. ——— has also indicated that they have devised a remedy for this issue, however the remedy for this problem has yet to be demonstrated as effective.

The second subset of wind turbine complaints run as follows:

The complainants state, and observations made by GOO Staff confirm that, at some locations that the cumulative noise emissions from the operation of a number of wind turbines, (blade whoosh), are exceeding the requirements set out in the CofA(Air), (in this case the CofA(Air) references the limits set in the “Interpretation For Applying MOE NPC Technical Publications To Wind Turbine Generators”). In the cases where GDO Staff have identified exceedances of the CofA, (noise levels measured between 44 dBA and 45 dBA utilizing NPC-l03 methodology with wind speeds of less than 6 m/s), there are between 37 and 52 wind turbines observable inside of a 3 km radius from the points of measurement.

The third subset of wind turbine complaints run as follows:

The complainants state, and GDO Staff have confirmed, that the noise emissions from the multiple wind turbines, (primarily at night), are considerably above the normal nighttime ambient noise levels previously encountered in that area. GDO Staff measurements utilizing the NPC-103 methodology confirm that when the turbines are not operating, the normal nighttime background ambient noise level varies between 27 and 29 dBA. When the turbines are operating, (excluding locations identified in the last subset), the noise levels in the area vary between 35 dBA and 37 dBA, which is effectively an 8 to 10 dB increase over the usual nighttime levels that they had been conditioned to prior to March of 2006/October 2008. …

Understandably the complainants [in the first and third cases above] in this particular circumstance are again not particularly receptive to our comments that the noise emissions from the wind turbines are in compliance with the CofA(Air) requirements, and that MOE has no grounds to proceed with any abatement/enforcement action. In this case two of the complainants have moved out of their homes, (along with their families), and have made financial settlements with ——— with ——— buying the homes/properties from the complainants.

In the case of the second set of complaints, (measured exceedance of the CofA(Air) standards utilizing NPC-l03 methodology), GDO staff have been informed by EAAB [Environmental Assessment and Approvals Branch] Staff, yourself among them, that NPC-103 methodology is not applicable to measuring noise emissions from multiple sources, (such as 37 wind turbines located inside a 3 km radius).

In all of the three cases above, District Office Staff are unable to confirm compliance, or identify non-compliance, utilizing the NPC-l03 measurement methodology, with the applicable standard, and subsequently take appropriate action. EAAB has knowingly issued a series of Certificates of Approval (Air) that are unenforceable.

Objective

In the short term, in terms of addressing at least the three wind turbine issues noted above, the most immediate objective of the GDO is to obtain a methodology by which multiple noise sources impacting a sensitive receptor can be measured to identify compliance or the lack thereof with the applicable standard/limit. In other words, Field Staff need an addendum to NPC-103, (or for that matter a new NPC), that sets out a methodology to measure noise emissions form multiple sources impacting on a sensitive receptor. This is essential not only for these “non-GEA” wind energy approvals, [but] also for identifying compliance with future GEA wind energy approvals.

In the long term, in terms of addressing the two transformer complaints, and the first wind turbine issue, the objectives are to:

(1) Address the circumstances where a new noise source has been placed into a very quiet location beyond the circumstances identified and contemplated by the NPC-232 Class 3 area, and:

(2) Address the circumstances whereby audible annoying/disruptive low frequency and near low frequency tones are present in the noise emissions from wind turbines and/or transformers, but are weighted against by the configuration of the A scale. …

G.W.T.
Provincial Officer
Badge # 132
Senior Environmental Officer
Guelph District Office
West Central Region
Ontario Ministry of the Environment
Tel: 519 626 4272
Fax: 519 626 4266

Download original document: “Multiple wind turbine noise level measurement”