Wind Energy Systems Zoning Ordinance

Emmet County 2 April 2013 Document No. MA1583-RPAC-001

Wind Energy Systems Zoning Ordinance Acoustic Review

AECOM Wind Energy Systems Zoning Ordinance

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Wind Energy Systems Zoning Ordinance Acoustic Review

Prepared for

Emmet County

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2 April 2013

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Quality Information Document Wind Energy Systems Zoning Ordinance

Ref

Date 2 April 2013

Prepared by Andrew Mitchell and Simon Moore

Reviewed by David Peoples

Revision History

Revision Revision Date Details

Authorised

Name/Position Signature

0 Internal Draft

1 02-Apr-2013 For Issue to Emmet County Andrew Mitchell Principal Acoustics Engineer



Table of Contents Executive Summary i 1.0 Introduction 1

1.1 Background 1 1.2 Scope of Review 1

2.0 Guidelines, Standards, and Literature 2 2.1 World Health Organization 2

2.1.1 Night Noise Guidelines for Europe, 2009 2 2.1.2 Guidelines for Community Noise, 1999 2

2.2 Michigan State 3 2.3 International Standards 4

2.3.1 New Zealand Standard 6808:1998 4 2.3.2 New Zealand Standard 6808:2010 4 2.3.3 South Australian Wind Farms Environmental Noise Guidelines 5 2.3.4 Other International Criteria 6

3.0 Letters, Comments, and Submissions 7 3.1 Review of Submissions Received by Emmet County 7 3.2 Michigan State University Extension Recommendation 7 3.3 The Potential Health Impact of Wind Turbines 8

4.0 Review of Proposed WES Zoning Ordinance 9 5.0 Summary of Recommendations 16

5.1 Noise Limits 16 5.2 Measurement and Assessment Methodology 16

Appendix A Nomenclature A



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Executive Summary AECOM has been commissioned by Emmet County to undertake an acoustic review of proposed changes to the Wind Energy Systems (WES) section of the Emmet County Zoning Ordinance.

A number of documents were reviewed as part of the work, including:

- the existing and proposed noise sections of the Emmet County Zoning Ordinance

- World Health Organization documents relating to night-time noise and community noise

- Michigan State wind energy systems noise guidelines

- International Standards and wind energy systems guidelines and regulations

- recommendations by Michigan State University Extension Land Use Educator Kurt Schindler, and the study referenced in his recommendations

- representations by Emmet County community to the proposed changes to the noise section of the zoning ordinance.

In summary, the following is recommended:

The recommendations for the noise limits are:

- proceed with the proposed limit change to 40 dB(A)

- consider the implementation of a “high amenity” 35 dB(A) criterion for low background noise areas or particularly noise sensitive areas

- define the Maximum Noise Level as a 10-minute Equivalent Continuous Sound Pressure Level (Leq,10min)

- remove the sentence “This sound pressure level shall not be exceeded for more than three consecutive minutes during any hour of the day”

- consider nominating the assessment location to be within 100 feet of a noise sensitive building or place rather than the property line or lease unit boundary of the WES site in question.

- define the measurement and assessment methodology for determining the ambient noise levels, and the operational WES noise levels.

The recommendations for the measurement assessment and methodology are:

- adopt the method to determine the ambient noise levels as defined in the South Australian Wind Farms Environmental Noise Guidelines (SA guidelines)

- adopt the method to determine the wind energy systems noise levels as defined in the SA guidelines

- adopt the method to assess the wind energy systems noise levels as defined in the SA guidelines

- provide further guidance regarding seasonal variation and when to measure

- include a requirement under the Maximum Noise Levels that the noise levels from the wind energy systems shall be free of special audible characteristics, when assessed in accordance with Appendix B of New Zealand Standard NZS 6808:2010.



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1.0 Introduction AECOM has been commissioned by Emmet County to undertake an acoustic review of the Wind Energy Systems (WES) section of the Emmet County Zoning Ordinance.

1.1 Background The current requirements for WES’s relating to noise as outlined in Section 2102-16 of the Emmet County Zoning Ordinance can be summarized as follows:

- 35 dB(A) maximum noise level when measured at the property lines of the site in question. This is applicable for all classes of WES defined in the ordinance (i.e. WES’s under 60 feet, WES’s over 60 feet, and Utility Grid WES’s).

- WES’s under 60 feet require a manufacturer’s specification sheet or similar documenting noise emission levels.

- WES’s over 60 feet require a noise report to be submitted with any application for a WES.

- Utility Grid WES’s require a noise report to be submitted with any application for a WES, which is prepared by a qualified professional and includes:

a description and map of the project’s noise-producing features including the range of expected noise levels, and the basis of expectation

a description and map of the noise sensitive environment, within 2 miles of the proposed facility

a survey and report that analyzes the pre-existing ambient noise (including seasonal variation) and the sensitive receptors located within 2 miles of the proposed site. Potential sensitive receptors at less windy or quieter locations than the project shall be emphasized and any problem areas identified

a description and map of the cumulative noise impacts with any problem areas identified

a description of the project’s proposed noise control features and specific measures proposed to mitigate noise impacts for sensitive receptors

The changes proposed by Emmet County are summarized as follows:

- Inclusion of the definition of a Qualified Acoustics Professional

- For all classes of WES’s, increase the maximum noise level to the greater of:

40 dB(A); or

the ambient L90 sound pressure level plus 5 dB(A) between the hours of 6 am and 10 pm, and the ambient L90 sound pressure level between the hours of 10 pm and 6 am.

- The maximum noise level for all classes of WES’s shall not be exceeded for any more than three consecutive minutes in any one hour period.

1.2 Scope of Review The scope of this review is as follows:

- Review, analyse and make recommendations regarding Emmet County’s Wind Energy System portion of the Emmet County Zoning Ordinance.

- Include scientific evidence and analyses supporting AECOM’s recommendations.

- Consider the documents, letters and comments that were provided to the Planning Commission in the review.

- Consider recommendations provided by Michigan State University Extension Land Use Educator Kurt Schindler’s recommendation and the study he referenced (The Potential Health Impact of Wind Turbines).



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2.0 Guidelines, Standards, and Literature

2.1 World Health Organization 2.1.1 Night Noise Guidelines for Europe, 2009

In 2009 the World Health Organization (WHO) published the Night Noise Guidelines for Europe (NNG) as a result of research undertaken by a working group of experts in Europe to provide scientific advice for the development of future legislation and policy action in the area of assessment and control of night noise exposure. The guidelines may be considered as an update and extension of the WHO Guidelines for Community Noise (1999). The main noise sources considered in the research are road traffic, neighbours, air traffic, recreation, rail traffic, construction and industry.

The NNG has summarized the relationship between night noise exposure and health effects which has been reproduced in Table 1, below. Table 1 Effects of different levels of night noise on the population’s health

Average night noise level over a year Lnight, outside Health effects observed in the population

Up to 30 dB(A) Although individual sensitivities and circumstances may differ, it appears that up to this level no substantial biological effects are observed. Lnight,outside of 30 dB is equivalent to the no observed effect level (NOEL) for night noise.

30 to 40 dB(A) A number of effects on sleep are observed from this range: body movements, awakening, self-reported sleep disturbance, arousals. The intensity of the effect depends on the nature of the source and the number of events. Vulnerable groups (for example children, the chronically ill and the elderly) are more susceptible. However, even in the worst cases the effects seem modest. Lnight,outside of 40 dB is equivalent to the lowest observed adverse effect level (LOAEL) for night noise.

40 to 55 dB(A) Adverse health effects are observed among the exposed population. Many people have to adapt their lives to cope with the noise at night. Vulnerable groups are more severely affected.

Above 55 dB(A) The situation is considered increasingly dangerous for public health. Adverse health effects occur frequently, a sizeable proportion of the population is highly annoyed and sleep-disturbed. There is evidence that the risk of cardiovascular disease increases.

Note: Lnight,outside is the night-time noise indicator (Lnight) of Directive 2002/49/EC of 25 June 2002: the A-weighted long-term average sound level as defined in ISO 1996-2: 1987, determined over all the night periods of a year; in which: the night is eight hours (usually 23.00 – 07.00 local time), a year is a relevant year as regards the emission of sound and an average year as regards the meteorological circumstances, the incident sound is considered, the assessment point is the same as for Lden. See Official Journal of the European Communities, 18.7.2002, for more details.

Based on the exposure-effects relationship described in Table 1, the WHO recommends the following night-time noise guidelines for the protection of public health:

- Night noise guideline (NNG) Lnight,outside = 40 dB(A)

- Interim target (IT) Lnight,outside = 55 dB(A)

2.1.2 Guidelines for Community Noise, 1999

The WHO published the Guidelines for Community Noise in response to growing noise pollution and an increase in number of complaints from people exposed to noise. Community noise is defined as noise emitted from all sources except noise at the industrial workplace. The main sources of noise are road, rail and air, industries, construction and public work, and the neighbourhood.

In relation to sleep disturbance the Guidelines for Community Noise specifically state:



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“If negative effects on sleep are to be avoided the equivalent sound pressure level should not exceed 30 dBA indoors for continuous noise. If the noise is not continuous, sleep disturbance correlates best with LAmax and effects have been observed at 45 dB or less. This is particularly true if the background level is low. Noise events exceeding 45 dBA should therefore be limited if possible. For sensitive people an even lower limit would be preferred. It should be noted that it should be possible to sleep with a bedroom window slightly open (a reduction from outside to inside of 15 dB). To prevent sleep disturbances, one should thus consider the equivalent sound pressure level and the number and level of sound events. Mitigation targeted to the first part of the night is believed to be effective for the ability to fall asleep.”

Furthermore, the Guidelines for Community Noise provide information in relation to annoyance which has been reproduced in Table 2. Table 2 Guideline values for community noise in specific environments

Specific environment Critical health effect(s) LAeq [dB] Time base

[hours] LAmax, fast [dB]

Outdoor living area Serious annoyance, daytime and evening Moderate annoyance, daytime and evening

55 50

16 16

- -

2.2 Michigan State The State of Michigan Energy Office, Department of Labor & Economic Growth has developed guidelines to assist local governments to develop siting requirements for WES’s.

The guidelines provide the following model conditions in relation to noise emissions from WES’s:

1074. On-site Use Wind Energy Systems and Anemometer Tower

D. Sound Pressure Level: On-site Use wind energy systems shall not exceed 55 dB(A) at the property line closest to the wind energy system. This sound pressure level may be exceeded during short term events such as utility outages and/or severe wind storms. If the ambient sound pressure level exceeds 55 dB(A), the standard shall be ambient dB(A) plus 5 dB(A).

1609. Utility Grid Wind Energy System, On-site Use Wind Energy System over 20 meters high, and Anemometer Towers over 20 meters high.

B. Sound Pressure Level: The sound pressure level shall not exceed 55 dB(A) measured at the property lines or the lease unit boundary, whichever is farther from the source of the noise. This sound pressure level shall not be exceeded for more than three minutes in any hour of the day. If the ambient sound pressure level exceeds 55 dB(A), the standard shall be ambient dB(A) plus 5 dB(A).

The guidelines provide commentary for justification of the noise emission levels, the main points are listed below:

- Normal conversation is in the range of 50-65 dB(A).

- EPA and World Health Organization documents indicate that 55 dB(A) is too low to produce hearing loss or long term health effects.1&2

- EPA has estimated that the distance between persons would have to be 4 meters before there would be any speech interference at the property line.1

- The World Health Organization notes that “80-90% of the reported cases of sleep disturbance in noisy environments are for reasons other than noise originating outdoors” and “habituation to night time noise events occurs.”2

- EPA has noted that the typical sound level reduction of buildings in cold climates is 17 dB (windows open) and 27 dB (windows closed) so 55 dB outdoors would be reduced to no more than 28-38 dB indoors.1

The commentary acknowledges that the guidelines are recommending basic standards for sound pressure levels, and that separate standards can be developed for infranoise [sic] (infrasound), low frequency noise, and tonal noise, which can have lower limits.

1 EPA, 1974. Protective Noise Levels: Condensed Version of EPA Levels Document. 2 World Health Organization, 1999. Guidelines for Community Noise.



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For example the Huron County ordinance reduces their standard by 5 dB(A) in the event audible noise from the wind energy system contains a steady pure tone.

It also notes that separate standards can be developed for residential and non-residential areas.

2.3 International Standards 2.3.1 New Zealand Standard 6808:1998

The noise limits prescribed by New Zealand Standard 6808:1998 The assessment and measurement of sound from wind turbine generators (NZS 6808:1998) were widely adopted for WES’s in New Zealand and Australia, prior to publication of NZS 6808:2010 and various Australian guidelines. The updated version published in 2010 includes a number of improvements and clarifications, but remains fundamentally similar.

NZS 6808:1998 sets an environmental noise emission limit for wind farms as the greater of 40 dB(A) or background noise3 (L95) plus 5 dB(A).

This approach recognises that background noise levels typically vary with wind speed and that the noise emissions from wind turbines are also wind speed dependent. As such, noise limits varying with wind speed are appropriate for wind turbines, given that different amounts of masking by background noise will be provided at different wind speeds. (This differs from typical industrial noise which is not dependent on wind speed and therefore is assessed under conditions with minimal wind, when the background noise levels, and thus masking, are lowest).

Under the methodology prescribed by the Standard, background noise levels are measured continuously in 10-minute periods over a period of at least 10 to 14 days and the measured noise levels are correlated with wind speed at turbine hub height to determine a relationship between background noise level and wind speed, which is then used to determine the noise criteria.

The Standard also makes provision for a penalty adjustment to be applied to the measured noise levels due to the wind farm if special audible characteristics including tonality, amplitude modulation, and impulsiveness are present in the wind farm sound. The adjustment is in recognition that special audible characteristics may increase the level of annoyance caused by the sound.

Section 5.3 of NZS 6808:1998 addresses the requirements for special audible characteristics. In particular, the Standard states:

5.3.1

Sound from a WTG that has special audible characteristics (clearly audible tones, impulses, or modulation of sound levels) is likely to arouse adverse community response at lower levels than a sound without such characteristics. At present, there is no simple objective procedure available to quantify special audible characteristics, and subjective assessment is therefore necessary, supported by objective evidence (e.g. frequency analysis) where appropriate.

5.3.2

When sound has a special audible characteristic, the measured sound level of the source shall have a 5 dB penalty applied. This is because the subjective reaction to a sound containing a special audible characteristic is generally found to be similar to a sound 5 dB louder, but without the special audible characteristic. A maximum penalty of 5 dB shall be applied by adjustment of the measured sound level by arithmetic addition of +5 dB.

2.3.2 New Zealand Standard 6808:2010

New Zealand Standard 6808:2010 Acoustics – Wind farm noise (NZS 6808:2010) is the current noise standard adopted in New Zealand for measurement and assessment of noise from WES’s. It is also widely referenced in Australia, and has been directly adopted in the wind farm guidelines used by the Australian state of Victoria.

NZS 6808:2010 is similar to NZS 6808:1998, with the following differences:

- The noise emission limits are the noise level exceeded 90% of the time (L90)

3 It is noted that the term “background noise” can be considered equivalent to the definition of “ambient noise” as given in the Michigan State guidelines and the Emmet County Zoning Ordinance.



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- A ‘high amenity’ noise limit is included for areas with very low background noise levels. In areas where the high amenity noise limit applies, the noise limit is the greater of 35 dB(A) or the background noise (L90) plus 5 dB(A) for a high amenity area, otherwise the limit remains the same as NZS 6808:1998 for other areas

NZS6808:2010 has similar provisions to NZS6808:1998 that recognise the possibility of special audible characteristics and provide for a penalty of up to 6 dB to measured WES sound levels if such characteristics are present. Unlike NZS6808:1998, NZS6808:2010 specifies how assessments for special audible characteristics shall be conducted in its Appendix B.

With respect to tonality NZS6808:2010 offers a simplified test method and a reference test method. In regard to the simplified test method it is stated that it may be carried out using one-third octave-band measurement equipment but if it does not indicate tonality it may still be necessary to use the reference method to confirm the presence or absence of tonality.

The reference method is that prescribed in Annex C to ISO 1996-2:2007 or an equivalent method. The reference method comprises recording the sound under assessment and post-processing the sound files using an algorithm defined in the standard to analyse the frequency content.

2.3.3 South Australian Wind Farms Environmental Noise Guidelines

The South Australian Wind Farms Environmental Noise Guidelines 2009 (SA guidelines) are used widely in Australia for the assessment of noise from WES’s (wind farms). The SA guidelines were prepared by the South Australian Environment Protection Authority and they state:

In accordance with these guidelines the wind farm noise level (adjusted for tonality if needed) should not exceed:

- 35 dB(A) at relevant receivers in localities which are primarily intended for rural living, or

- 40 dB(A) at relevant receivers in localities in other zones, or

- the background noise (LA90,10minute) by more than 5 dB(A),

whichever is the greater, at all relevant receivers for wind speed from cut-in to rated power of the WTG (wind turbine generator) and each integer wind speed in between.

The background noise should be as determined by the data collection and regression analysis procedure recommended under these guidelines (Section 3). It should be read from the resultant graph at the relevant integer wind speed.

An adjustment for tonality is applied under the SA guidelines. In relation to tonality, the SA guidelines state:

If tonality is a characteristic of the WTG noise, 5dB(A) should be added to the predicted or measured noise level from the wind farm.

To help determine whether there is tonality, the method and results of testing (such as in accordance with IEC 61400 11) carried out on the proposed WTG model to determine the presence of tonality should also be specified in the development application.

The SA guidelines also provide comment on annoying characteristics as follows:

These guidelines have been developed with the fundamental characteristics of noise from a wind farm taken into account. These include the aerodynamic noise from the passing blades (commonly termed ‘swish’) and the infrequent and short-term braking noise.

However, annoying characteristics that are not fundamental to a typical well-maintained wind farm should be rectified. Such characteristics may include infrasound (low frequency noise below the audible frequency range that manifests as a rattle in lightweight materials such as glass) or adverse mechanical noise (perhaps generated as a failure of a component).

The SA guidelines can be found at http://www.epa.sa.gov.au/xstd_files/Noise/Guideline/windfarms.pdf



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2.3.4 Other International Criteria

A comparison of international standards for wind farm noise criteria was undertaken by Sonus Pty Ltd4 in a report prepared for the Clean Energy Council (Australia). The comparison is reproduced in Table 3. The full report can be found at:

http://www.cleanenergycouncil.org.au/dms/cec/reports/2010/Sonus-wind-farm-technical-paper-environmental-noise/Sonus%20wind%20farm%20technical%20paper%20-%20environmental%20noise.pdf

Table 3 Comparison of international wind farm standards (Reproduced from Sonus / Clean Energy Council Australia Report)

Assessment Procedure Country of Origin Objective Standard Comments

Sweden Base noise limit: 40 dB(A) Low background areas: 35 dB(A)

The approach does not provide a definition for a low background area.

Denmark Noise limit: 44 dB(A) @ 8m/s 42 dB(A) @ 6m/s For sensitive areas such as institutions, allotment gardens and recreation: Noise limit: 39 dB(A) @ 8m/s 37 dB(A) @ 6m/s

No background noise limit is applied. The noise limits are determined for wind speeds taken at 10m above the ground.

France Background noise limit margin: 5 dB(A) – day time Background noise limit margin: 3 dB(A) – night time

Based on a background noise measurement made at a wind speed of 8m/s

The Netherlands Noise limit: 40 dB(A) at night increasing incrementally up to 50 dB(A) at 12m/s

United Kingdom Base noise limit: 40 dB(A) (day time) Base noise limit: 43 dB(A) (night time) Background noise limit margin: 5 dB(A). The greater of the above limits applies.

The limits are a 90th percentile level (LA90). The LA90 is inherently less than the equivalent noise level. The UK assessment procedure indicates the LAeq from a wind farm is typically of the order of 2 dB(A) greater than the LA90

The procedure notes that the recommended noise levels take into account “swish”.

USA (Illinois) (Reference TD178-01F06)

Base noise limit: 55 dB(A) (day time) Base noise limit: 51 dB(A) (night time)

The noise limits are determined for an 8 m/s wind speed taken at 10m above the ground. There are no uniform noise standards in the USA, with local counties establishing their own approaches which vary considerably.

4 Wind Farms Technical Paper, Environmental Noise, prepared for the Clean Energy Council, November 2010.



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3.0 Letters, Comments, and Submissions

3.1 Review of Submissions Received by Emmet County A summary of the submissions received by Emmet County in response to the proposal to alter the allowable wind turbine noise levels are provided below:

- Most submissions received opposed the proposal on the basis of adverse impact to the amenity (quietness) of the area

- A few of the submissions received also opposed the proposal on the basis of adverse health impacts

- One of the submissions received was in favour of altering the allowable noise limit on the basis of Emmet County avoiding litigation in response to refusing future WES developments.

There were other reasons cited in response to the proposal however these were mainly related to light and as such are not applicable to the proposal to alter the noise limits.

There are representations which reference the WHO publications (which have been summarized in Section 2.1) and the International Organization for Standardization ISO 1996:19715.

The reference to ISO 1996:1971 notes that the “ISO standards recommend a base limit of 35-40 dB(A) for rural and suburban daytime limits and 25-30 dB(A) for night limits.” We note that the ISO/R 1996:1971 standard was withdrawn on September 1, 1982. As such, we have reviewed the current version of this standard, ISO 1996-1:2003 Acoustics – Description, measurement and assessment of environmental noise – Part 1: Basic quantities and assessment procedures, and ISO 1996-2:2007 Acoustics – Description, measurement and assessment of environmental noise – Part 2: Determination of environmental noise levels. Neither of these standards provide guidance on acceptable community noise levels. ISO 1996-1:2003 notes “This part of ISO 1996 does not specify limits for environmental noise.”

3.2 Michigan State University Extension Recommendation Michigan State University Extension Land Use Educator Kurt Schindler’s recommendation in regard to the proposed alterations to the Emmet County Zoning Ordinance, Section 2102-16 Wind Energy Systems (WES’s) is shown in Figure 1. In summary, the recommendation tends to support the proposed change to 40 dB(A) on the basis that it may be hard for regulators to justify the current 35 dB(A) limit.

Figure 1 Excerpt: Michigan State University Extension Land Use Educator's review March 7, 2012

5 Email from William Marshall to Tammy Doernenburg “RE: proposed wind turbine ordinance amendment”, 6 December 2012.



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3.3 The Potential Health Impact of Wind Turbines In Kurt Schindler’s recommendation, the study by the Chief Medical Officer of Health of Ontario, Canada, The Potential Health Impact of Wind Turbines was referenced.

The report was prepared by a technical working group comprised of members from:

- the Ontario Agency for Health Protection and Promotion (OAHPP)

- the Ministry of Health and Long-Term Care (MOHLTC)

- several Medical Officers of Health in Ontario

- and support from the Council of Ontario Medical Officers of Health (COMOH)

The report provides the following conclusion:

The review concludes that while some people living near wind turbines report symptoms such as dizziness, headaches, and sleep disturbance, the scientific evidence available to date does not demonstrate a direct causal link between wind turbine noise and adverse health effects. The sound level from wind turbines at common residential setbacks is not sufficient to cause hearing impairment or other direct health effects, although some people may find it annoying.

It is noted that the conclusion is based on a receiver noise level of no more than 40 dB(A) from the wind turbines.



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4.0 Review of Proposed WES Zoning Ordinance AECOM’s review of the proposed zoning ordinance has identified the following matters which should be given further consideration. Table 4 Review of Proposed WES Zoning Ordinance

Comment No.

Section Ref. AECOM Review Comment AECOM Recommendation

1 A Definitions

The term Maximum Noise Level is not defined.

This can lead to ambiguity for both assessment and measurement of the WES noise emission levels.

It is common practice to define this term with a noise measurement metric and time. The most common metrics used are the equivalent noise level (Leq) and noise level exceeded 90% of the time (L90), and the most common time period used is 10 minutes.

Define the maximum noise level as “Leq,10min” (Equivalent Continuous Sound Pressure Level over a 10-minute measurement period). The Leq noise level is suggested as it is commonly used, and sound emission data from wind turbine manufacturers is most commonly provided in this format.

2 B.6 C.6 D.5

Maximum Noise Levels

The proposed ordinance states that the maximum noise levels “shall not be exceeded for more than three consecutive minutes during any hour of the day”.

There would be practical challenges associated with assessing whether compliance is achieved with such a criterion. This type of criterion does not lend itself to automated measurement using a noise logger, and would most likely need to be assessed through sound level measurements undertaken in person by a qualified acoustics professional. The practical issue with this is that the noise levels from the WES at any particular assessment location may vary depending on wind speed and direction. Multiple visits may be required to the site to assess the noise levels across a range of wind conditions. Timing the visits with the required wind conditions would be a practical challenge. On this basis, noise criteria that can be more readily assessed using automated measurement methods are recommended.

AECOM has also considered the possibility that the term “consecutive”

Remove the sentence “This sound pressure level shall not be exceeded for more than three consecutive minutes during any hour of the day”.



10

Comment No.


is in error and is really intended to mean “cumulative” (as it is in the Michigan State guidelines). Changing this term to “cumulative” is the same as considering the noise level exceeded 5% of the time (L05), however, this is not recommended since it would be very difficult to assess compliance against an L05 criterion as this would be controlled by short-term (and most likely extraneous) noise sources.

3 B.6 C.6 D.5

Maximum Noise Levels

Under the proposed changes to the WES ordinance, the maximum noise levels would be increased from a fixed limit of 35 dB(A) to:

- the greater of 40 dB(A) or the ambient noise level + 5 dB, during the daytime (6am to 10pm); and

- the greater of 40 dB(A) or the ambient noise level, during the night-time (10pm to 6am).

With the proposed increase the maximum noise levels remain generally more stringent than the 55 dB(A) limit proposed by the Michigan State guidelines. The proposed increase and inclusion of the “ambient plus 5 dB(A)” is consistent with criteria in use in The Netherlands, The United Kingdom, New Zealand and Australia. Furthermore the baseline criterion is similar to that in use in Sweden and more stringent than Denmark.

The WHO recommends a 40 dB(A) outdoor night noise exposure which is consistent with this proposal. The recommendations by Kurt Schindler and the report he referenced also support the proposed limit.

It is noted that a number of the standards and guidelines recommend a “high amenity” limit of 35 dB(A) for areas that are particularly sensitive to noise, however this is used in conjunction with the “ambient plus 5 dB(A)” term as well.

The proposed limit change is reasonable. Consideration should be given to a “high amenity” approach for certain low background or noise sensitive areas.



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Comment No.


4 B.6 C.6 D.5

Location where Maximum Noise Levels are Assessed

Under the proposed Zoning Ordinance, the maximum noise levels are assessed “at the property lines or the lease unit boundary of the site in question, whichever is farther from the source of the noise”. This approach ensures that noise impacts from the wind farm are controlled to the specified level on all parts of adjoining properties. However, it also potentially results in areas of rural properties being protected which are well beyond the noise sensitive area of the building or external locations that are frequented by persons residing, working or sleeping at the premises, or in the case of land set aside as a park or reserve or for public enjoyment, by members of the public.

Consideration should be given to the assessment location being an area within 100 feet (30 meters) of a noise sensitive building or place, outside the boundary of the site of the WES. Suggested wording is: “The noise limits shall apply at sites outside the property lines or lease unit boundaries of the WES as follows:

(a) At any point that is both within the legal boundary of any property on which a dwelling is located and within 100 feet of the dwelling;

(b) At any point within the legal boundary of any public park or reserve”

5 General Determination of Ambient Noise Levels

The noise limits proposed by the zoning ordinance relate to the ambient noise levels but the zoning ordinance does not specify how the ambient noise levels are to be determined.

It will be necessary to ensure there is a consistent approach to determining the ambient noise levels, as there are a range of factors that could influence the level of ambient noise determined for any particular location, including:

- measurement duration, number of samples, averaging method (if any)

- time of day (insect and bird noise is often a dominant source near dawn and dusk)

- precipitation - wind conditions - seasonal variations - proximity of measurement location to man-made sources such as

Given the considerable number of factors that need to be defined to ensure consistent measurement of ambient noise levels, it is recommended that the Zoning Ordinance should adopt an existing standard or guideline and require that the ambient noise levels be determined in accordance with that standard or guideline, rather than attempting to specify details of the measurement method in the Zoning Ordinance itself.

The SA guidelines provide a robust and very clearly defined methodology for determining ambient noise levels and it is therefore recommended to adopt the method defined in the SA guidelines. This method can be summarised, as follows:

Ambient noise (L90) is measured at relevant noise sensitive receiver locations at continuous 10-minute intervals and particularly over the range of wind speeds at which the WES’s operate. The data must adequately represent conditions at the site and cover approximately



12

Comment No.


traffic noise - presence of extraneous noise sources not normally part of the

ambient noise environment. Given the above, it is considered essential that the method by which the ambient noise is to be determined be defined in the ordinance.

Well-defined methods for determination of ambient noise levels are provided by the SA guidelines and NZS:6808.

2,000 intervals with at least 500 intervals representing the worst case wind direction.

Wind speed is measured in intervals that correlate with the ambient noise measurements at relevant receiver locations. The worst case wind direction is defined as being within 45° either side of the direct line between the nearest proposed WES and relevant receiver.

The ambient noise data versus wind speed is plotted on a scatter graph for each relevant receiver. A best fit regression analysis (from linear up to third order) is used to fit a regression line to the ambient noise level data. The regression line is then used for the determination of the ambient noise level. An example regression analysis is presented in Figure 2, following this table.

An alternative method to using regression analysis (although not part of the SA guidelines) is the use of “bins”, whereby the average noise is calculated for each integer wind speed e.g. for 7 m/s, all noise levels measured at wind speeds between 6.5 and 7.4 m/s are used to calculate the 7 m/s wind speed noise level. This method is detailed in IEC 61400-11:2012 Wind turbines – Acoustic noise measurement techniques and is referred to as a possible analysis methodology by NZS 6808:2010

Consideration should be given where seasonal variations will influence ambient noise levels (i.e. snow, deciduous trees etc).

6 General Methodology for Measurement of WES Noise

There is no methodology defined for the measurement of WES noise specified in the proposed Zoning Ordinance. It will be necessary to ensure there is a consistent approach to measuring the noise levels (since this is used for assessment of compliance), which will vary over a range of wind speeds and directions.

Whilst ANSI S12.18 (as referenced by some noise ordinances in other counties) provides good practice guidelines for the measurement of noise in general, it is not specific to the measurement of noise from

Given the considerable number of factors that need to be defined to ensure consistent measurement of ambient noise levels, it is recommended that the Zoning Ordinance should adopt an existing standard or guideline and require that the ambient noise levels be determined in accordance with that standard or guideline, rather than attempting to specify details of the measurement method in the Zoning Ordinance itself.

The SA guidelines provide a robust and very clearly defined



13

Comment No.


WES’s.

Measurement of noise level emissions from WES’s in terms of Equivalent Continuous Sound Pressure Levels (Leq) can be difficult when using automated logging equipment. Wind-induced noise and other extraneous noise sources typically have a significant influence on the Leq level, resulting in measurements not representative of the WES noise..

Compliance monitoring of WES’s is therefore commonly undertaken by measuring the noise level exceeded 90% of the time (L90). This is the same method adopted for measuring the ambient noise level, as it reduces the influence from short term extraneous noise sources. This makes it easier to use automated noise logging equipment for monitoring over a long period to capture a range of wind speeds and directions. The L90 level is typically taken as equivalent to the Leq level for the purpose of WES compliance measurements; however, a +1.5 dB adjustment is applied under some standards (e.g. Australian Standard 4959:2010 – Acoustics – Measurement prediction and assessment of noise from wind turbine generators) to correct the measured L90 to an Leq for comparison to the noise criteria.

It is also beneficial to prescribe the minimum number of data points to be collected and the wind conditions under which the data is to be collected.

Well-defined methods for measurement of WES noise levels are provided by the SA guidelines and NZS:6808.

methodology for determining ambient noise levels and it is therefore recommended to adopt the method defined in the SA guidelines. This method can be summarised, as follows:

WES noise is measured at relevant noise sensitive receiver locations at continuous 10-minute intervals and particularly over the range of wind speeds at which the WES’s operate. The measurements are performed in terms of L90 sound pressure levels, but are considered equivalent to Leq levels for assessment purposes.

The data must adequately represent conditions at the site and cover approximately 2,000 intervals with at least 500 intervals representing the worst case wind direction.

Wind speed is measured in intervals that correlate with the ambient noise measurements at relevant receiver locations. The worst case wind direction is defined as being within 45° either side of the direct line between the nearest proposed WES and relevant receiver.

The correlated wind speed and WES noise data are plotted to give a standard graph for WES noise at each relevant receiver. A best fit regression analysis (from linear up to third order) is used to fit a regression line to the WES noise level data. The regression line is then used for the determination of the WES noise level, and comparison with the previously determined ambient noise level.

7 General Methodology for Assessment of WES Noise

There is no methodology defined for the assessment of WES noise either at planning or post-construction compliance stage. Whilst a qualified acoustics professional should be competent at determining a suitable assessment procedure, providing a methodology will ensure a

As per comments 5 and 6 it is recommended to adopt the method defined in the SA guidelines.



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Comment No.


consistent approach by all professionals for all proposed developments across Emmet County.

8 General Seasonal Variations

Ambient noise levels at locations without significant ‘man-made’ noise can be subject to significant variation due to seasonal factors such as snow and vegetative cover, wildlife activity, and prevailing wind directions. The existing and proposed ordinance requires this to be taken into account for Utility Grid WES’s; however it does not provide any further guidance.

The ambient noise levels should be captured at the time of the year when background noise levels are lowest at the location where the WES is to be constructed. If it is not clear which period of the year the background noise levels are the lowest, then background noise measurements may need to be undertaken at various times during the year to establish if there is any significant variation between seasons and the lowest background noise levels should be used for the setting of criteria.

9 General Special Audible Characteristics (SAC’s)

There is no discussion or mention of SAC’s.

Certain characteristics of noise can be more annoying than a steady, broadband noise signal. These characteristics include:

- tonality - amplitude modulation - low frequency noise - infrasound. NZS 6808:2010 provides a prescriptive assessment of SAC’s in Appendix B.

Include a requirement under the Maximum Noise Levels that the noise levels from the WES’s shall be free of SAC’s, when assessed in accordance with Appendix B of NZS 6808:2010.



15

Figure 2 Example of a typical regression analysis

Fit Line Eqn = -0.003144x3 + 0.208098x2 - 1.368082x + 33.039892R² = 0.280709

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Wind speed at Hub Height [ms-1]

Background Noise Level vs Wind Speed

Background Noise Data Polynomial fit

Below Wind TurbineCut-In Wind Speed

Above Wind Speed at Wind Turbine Rated Power



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5.0 Summary of Recommendations

5.1 Noise Limits The recommendations for the noise limits are:

- proceed with the proposed limit change to 40 dB(A)

- consider the implementation of a “high amenity” 35 dB(A) criterion for low background noise or particularly noise sensitive areas

- define the Maximum Noise Level as a 10 minute Equivalent Continuous Sound Pressure Level (Leq,10min)

- remove the sentence “This sound pressure level shall not be exceeded for more than three consecutive minutes during any hour of the day”

- consider the assessment location to be within 100 feet of a noise sensitive building or place rather than the property line or lease unit boundary of the site in question.

5.2 Measurement and Assessment Methodology The recommendations for the measurement assessment and methodology are:

- adopt the method to determine the ambient noise levels as defined in the SA guidelines

- adopt the method to determine the WES noise levels as defined in the SA guidelines

- adopt the method to assess the WES noise levels as defined in the SA guidelines

- provide further guidance regarding seasonal variation and when to measure

- include a requirement under the Maximum Noise Levels that the noise levels from the WES’s shall be free of SAC’s, when assessed in accordance with Appendix B of NZS 6808:2010.



AAppendix A

Nomenclature



A-1

Appendix A Nomenclature A-Weighting The A-weighting scale is designed to adjust the absolute sound pressure levels to correspond

to the subjective response of the human ear.

dB(A) A-weighted noise levels are expressed in units of dB(A).

Ambient noise The noise present in an area, excluding noise from the particular source of interest. When measured as an L90 noise level, this is also termed “background noise”.

Frequency The number of cycles per second, where 1 cycle per second is equal to 1Hz. The human ear responds to sounds of frequency 20 Hz to 20,000 Hz.

Leq Equivalent (energy averaged) noise level measured over a time period. This noise descriptor is commonly used in environmental noise policies and assessments. The time period the measurement is averaged over and frequency weighting may be included in the subscript, i.e. LAeq,10min

Lmax The maximum noise level recorded over a measurement period. The frequency weighting may also be included in the subscript, i.e.LAmax

L95 The noise level exceeded for 95% of the measurement period. This descriptor is used to measure and assess the wind farm noise level, as it is less susceptible to the influence of extraneous noise than the equivalent noise level. The time period the measurement is taken over, and frequency weighting may be included in the subscript, i.e. LA95,10min

L90 The noise level exceeded for 90% of the measurement period. This descriptor is used to measure and assess the wind farm noise level, as it is less susceptible to the influence of extraneous noise than the equivalent noise level. The time period the measurement is taken over, and frequency weighting may be included in the subscript, i.e. LA90,10min

L10 The noise level exceeded 10% of the measurement period. This descriptor is often used to represent the short term maximum (or intrusive) noise level. The time period the measurement is taken over, and frequency weighting may be included in the subscript, i.e. LA10,10min

L05 The noise level exceeded 5% of the measurement period. The time period the measurement is taken over, and frequency weighting may be included in the subscript, i.e. LA05,10min

Lden The Leq noise level over a 24 hour period, with penalties added for noise during the evening and night time hours. During the evening period (19:00-23:00) 5 dB is added. During the night time period (23:00-07:00) 10 dB is added.



A-2

SAC Special Audible Characteristics

Tonality A characteristic of noise, describing a sound that contains a perceptible pitch or tone.

Infrasound Infrasound is sound that occurs at frequencies lower than the normal hearing range of the human ear. This is typically defined as sound at frequencies of less than 20 Hz. Although infrasound is generally thought of as not being audible, it can become audible if the level is high enough.

Amplitude Modulation

Amplitude modulation refers to a regular time varying modulation in the noise level of a source

Low Frequency Noise

Low frequency noise typically describes noise at the lower end of the frequency range normal human hearing, generally frequencies from nominally 20 Hz to 200 Hz.

Documents

Wind Energy Systems Zoning Ordinance