Ambrose, Rand Peer Review, Douglas Wind Farm, Massachusetts

Stephen E. Ambrose, INCE, Bd. Cert. Robert W. Rand, INCE
July 26, 2013

Subject: Peer-Review: Sound Survey and Analysis Report

Proposed Douglas Woods Wind Farm, Douglas, Massachusetts Reference: Acoustic Analysis, Atlantic Design Engineers, October 19, 2010

… we are submitting our peer-review of the October 19, 2010 Acoustic Analysis, Douglas Woods Wind Farm, a report submitted by Atlantic Design Engineers (ADE), Inc. for a wind turbine facility proposed by American Pro Wind, LLC in Douglas and adjacent to Webster, Massachusetts.

The review was performed by Stephen Ambrose, INCE, Bd. Cert. of SE Ambrose & Associates and Robert Rand, INCE of Rand Acoustics. Each has over 30 years of professional experience in acoustics with expertise in environmental noise measurement and community impact assessment.

We find that the proposed facility will cause an adverse noise impact for people living east of Upper Gore Road in Webster, Massachusetts, and along Webster Street (Rte. 16) and Old Douglas Road to the north. Our professional evaluation of ADE’s submittal and extensive experience reviewing wind turbine facilities concludes:

1. The proposed facility is certain to exceed the MassDEP noise limits. There are no reliable noise control engineering options for complying with the noise limits without using significant separation distance. This project lacks the required separation distance needed for compliance with the MassDEP noise limits.


2. The proposed facility has high probability to create a nuisance and cause harm or injury to neighbors as defined by the MassDEP. Harm, injury, and home abandonment have been documented at similar wind power facilities. The same outcome is expected in Webster.


Pages 19 and 20 of the Peer Reviewed Report are reproduced here:

Nuisance from Low Frequency Noise

The Mass DEP regulations and the Webster Town codes do not directly regulate or provide guidance on low frequency noise emissions from power generation facilities. The A-weighted sound level by design filters out the low frequency noise contributions so that it is not possible to effectively evaluate for the potential for low frequency community noise impacts. Officials reviewing wind turbine proposals should understand the potential for an adverse community reaction to low frequency noise. Wind turbines have proven themselves to be a significant producer of low frequency energy.

ADE’s report was silent on the potential for low frequency noise impacts and resulting nuisance. This is remarkable because since at least 1987, low frequency community noise impacts have been known and published by a number of acoustic researchers, among others, the US Department of Energy [8].

Much more has been learned on the community response to large industrial wind turbines since the ADE report was issued in 2010. The following discussion addresses a method for assessing impacts of low frequency noise emissions, which are demonstrated to be audible and capable of creating a nuisance at residences near the Douglas Woods Wind Farm.

Denmark has a long and well-established history with wind turbines. We understand that recent replacement of older, smaller wind turbines with newer, larger industrial wind turbines has provoked community resistance and complaints. The Danish Ministry of Health has an industrial indoors low frequency night noise limit of 20 Lpa,LF (10-160 Hz A-weighted one-third octave bands) which provides an established metric for assessing for and preventing potential low frequency noise disturbance indoors. In 1999 the Dutch Foundation for Noise Nuisance (NSG) published a guideline for low frequency noise [9] which became a basis for case law. The criteria are based on hearing thresholds for the 10% most sensitive people in an ontologically unselected population aged 50-60 years. These 10% thresholds are typically about 4-5 dB lower than the average threshold for ontologically normal young adults (18-25 years) as given in ISO 226. Denmark extended the law to regulate industrial wind turbines effective January 1, 2012.

For this review, low frequency emissions from the proposed Douglas Woods Wind Farm were assessed by using known one-third octave band sound levels for the Nordex N100/2500 at 1100ft (Shirley study, location R2). Example house noise reductions used in the Danish law are under controversy as they allow higher interior sound levels a percentage of the time [10]. House noise reduction values were taken from the Epsilon 2006 study Table 4.3-1 [11]. The expected interior sound levels from the Douglas Woods Wind Farm were plotted with the NSG hearing threshold and the Danish 20 dBA low frequency noise limit as shown in Figure 2-1. The Douglas wind turbines are expected to exceed the limits set in Denmark law to prevent nuisance.

We understand that while the Danish indoors industrial noise limits limits have no direct legal bearing in Massachusetts, they are validated by medical research and used by the Danish state for preventing nuisance. They should be considered a validated reference and criterion for preventing nuisance from industrial low frequency noise.

Figure 2-1. Indoors, low-frequency noise impact at 1100 feet, based on Nordex N100/2500 noise levels measured at Location R2, Shirley, Wisconsin, December 2012.

This review’s indoors low frequency calculation determined the following.

Conclusion: Expected indoors noise levels from the Douglas facility exceed reference limits established to prevent nuisance from low-frequency industrial noise

— At 1100 feet, the distance to nearby homes, the proposed Douglas Woods Wind Farm would produce audible low frequency sound indoors at 27 Lpa,LF, which strongly exceeds the Danish 20 Lpa,LF limit indoors. Exceedences of 20 Lpa,LF rapidly escalate annoyance and levels nearing 30 dBA are considering strongly annoying. A nuisance condition is expected.

— This low frequency analysis determined that the difference in decibels between Lpa,LF and dBA was 21 dB (example 48 dBA, 27 Lpa,LF). This determination is buttressed by the research published by Moller et al, 2011, who found a similar, 20-dB difference between dBA and Lpa,LF for the Vestas V112-3MW turbine. The similar results suggest a predictable degree of low frequency noise from the large turbines of this size (blades 50-56 meters in length).

— For planning to avoid indoors low frequency impacts, the wind turbine’s outdoors dBA level should be kept below 40 dBA at nearby homes. That criterion should keep indoors low frequency intrusive noise below 20 Lpa,LF, the protective maximum limit on nuisance from low frequency noise established by the Danish Ministry of Health.

— From this analysis, the distance to the 20 Lpa,LF Danish limit from the Nordex N100/2500 wind turbines was computed to be 2460 feet. In other words, about a 1/2 mile minimum setback would be needed to reduce the indoors, low frequency noise levels to the 20 Lpa,LF protective limits established by the Danish Ministry of Health. Larger distances would be needed as a design safety margin to assure no low frequency impacts. Distances of a 1/2 mile or more for setback to prevent nuisance are not available at the Douglas Woods Wind Farm.

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