Sound Judgement...

 Yesterday I posted a story about the Wisconsin Public Service Commission rejecting a wind project based on a noise study conducted at the Shirley wind farm.

Four consultants participated in the Shirley study.  Hessler Associates, Dr.Paul Schomer, Bruce Walker and Rob Rand. Two of these consultants have a history in Cape Vincent ,Hessler Associates and Paul Schomer.  

  
Paul D. Schomer of Schomer & Associates Inc., Dr. Schomer is chairman of the International Organization for Standardization working group on environmental noise and chairman of the American National Standards committee on noise, among other leadership roles in noise measurement. A group of Cape Vincent  residents commissioned Dr. Schomer; NY to evaluate the pre-construction noise studies conducted by Hessler and Associates. His findings contradict the studies done by Hessler Associates Inc.

The executive summary of his report is reproduced on this page.

 His full report can be accessed by clicking the link at the end of this post.

Background sound measurements and analysis in the vicinity of Cape Vincent, NY

May 11, 2009 by Paul Schomer, Ph.D., P.E.

Summary:

The acoustic consulting engineering firm Hessler Associates, Inc., Haymarket, Virginia produced two sound level assessment reports for two wind projects proposed for Cape Vincent, New York: the first report in 2007 for BP and the second report in 2009 for AES-Acciona.

Because there were concerns early on among local citizens that the BP report was misleading, the Wind Power Ethics Group (WPEG) contracted with Schomer and Associates, Champaign, Illinois to conduct an independent background sound survey of Cape Vincent. Hessler's BP study for the Cape Vincent Wind Power Facility appears to have selected the noisiest sites, the noisiest time of year, and the noisiest positions at each measurement site. Collectively, these choices resulted in a substantial overestimate of the a-weighted ambient sound level, 45-50 dB according to Hessler.

This study was designed to address a number of flaws noted in Hessler's BP study. First, a summer survey was planned so it would not coincide with the emergence of vocal adult insects (e.g., fall crickets and cicadas on August 1). Two monitoring sites were selected within the Town of Cape Vincent. One site was a rural residence and the other a small dairy farm. At each of these sites, two sound level meters and a single small weather station were run for one week of continuous data collection. At each site one meter was set up close to the house or farm building and a road. This site was called the "Hessler" position, because it was typical of sites selected by Hessler for his studies in Cape Vincent. The other position was called the
Community position and it was located back away from the noise influences of roads, houses and farm operations. The Community position also reflected guidelines adopted by the Cape Vincent Planning Board whereby sound levels were to be measured at the property lines, not residences.

The analysis of the spectral (frequency) content of the sound showed that much of the difference in sound levels between Hessler's study and this study was attributable to insect noise, sounds near 5000 Hz. Hessler failed to remove insect sound from his data and recalculate A-weighted sound levels, even though he previously (2006) recommended this procedure to other scientists and engineers in a professional journal publication. Had he followed his own advice, ambient sound levels would have been more comparable to the results in this study.

Furthermore, and more importantly, wind turbine sound spectra are low frequency and mid frequency phenomena; therefore, higher frequency insect noise will not mask wind turbine sounds. So even if insect noise was present year round instead of for a few weeks it should still not be included in the ambient because it provides little or no masking of the wind turbine sound.

Other examples of Hessler's misleading choices include arbitrarily discarding sound data from one of his sites because the levels were too low. Remarkably, the levels at that site were more comparable to this study. Also, Hessler described position 3 in the BP study as "representative of a typical residence along NYS Rte 12E." However, he failed to show that the trailer in the photograph was a field office for a construction company installing a new Town of Cape Vincent water district. Furthermore, at the back of the trailer, out of view, was a marshaling yard for trucks, supplies and heavy equipment. The choice of this site and suggesting it is a typical residence was very misleading.

The accurate measurement of spectrally-relevant ambient sound is important because these levels are used by wind developers to assess wind turbine noise impacts on nearby, nonparticipating residents. Local Cape Vincent Planning Board guidelines suggest these impacts should not exceed 5 dB above the A-weighted ambient at the property lines of non-participating residents. New York State noise assessment policy states any new sound that exceed 6 dB above the A-weighted ambient should undergo a detailed assessment and the developer is required to mitigate any excessive noise. Therefore, using an inaccurate, elevated A-weighted ambient level, such as 47 dB, allows wind developers to place wind turbines much closer to non-participating residents in such a way that the A-weighted wind turbine noise level will be 52 dB (e.g., 5 dB above Hessler's elevated ambient level). A much more accurate and typical ambient level is 30 dB, which is an average of both "Hessler" and Community positions during daytime, evening and nighttime periods from this study. Using 30 dB as a typical A-weighted ambient level would then require wind developers to plan a wind farm where predicted noise at non-participating property lines would not exceed 35 dB, or 5 dB above this study's A-weighted ambient level. In summary, to adequately protect rural residents that are not participants in proposed wind farms it is essential to have accurate, unbiased assessments of ambient sounds.

In conclusion:

1. The Hessler position at a measurement site systematically and significantly yields higher sound levels than does the Community position.

2. The sound levels measured in this study show Cape Vincent to be a quiet rural area, much as depicted by the data for Hessler's position 4.

3. Measurements, such as those conducted at Hessler's position 3, are not indicative of the noise environment of typical residences in the Cape Vincent area.
 For position number 3,  Hessler chose to use a marshaling yard for trucks, supplies and heavy equipment to represent a typical residence  .

4. Failure to remove insect noise in Hessler's study violated his own recommended survey and analytical techniques and substantially misrepresented typical ambient sound levels.

5. In assessing potential noise impacts from wind turbine development, rather than using 45-50 dB A-weighted levels as suggested by Hessler, a more accurate level would be 30 dB, which is the average value for the daytime, evening and nighttime L90 sound levels observed at both the "Hessler" and Community positions for sites A and B in this study. Arguably, the level should be down at 20 to 25 dB, since an A-weighted L90 of 20 dB occurs during the quietest nighttime hours, and the A-weighted L90 for the whole 9-hour night is 25 dB.
 ~~~
April 14, 2010 St. Lawrence Wind power  arranged to have Hessler give a two-hour rebuttal to Dr.Schomers evaluation of his work.
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 In response to Hesslers presentation Schomer and Associates sent the following letter to Cape Vincent Town Supervisor .

Transcript of the letter ~

Mr. Urban Hirschey – Supervisor
Town of Cape Vincent
1964 NYS Rte 12E
Cape Vincent, NY 13618
April 23, 2010
Dear Supervisor Hirschey:

This letter is my response to Mr. David Hessler's April 14, 2010 presentation to the Cape Vincent
Planning Board regarding my report, “Background sound measurements and analysis in the vicinity of Cape Vincent, New York.”
Mr. Hessler continues to ignore important facts. Specifically, he:

1. Mixes winter and summer wind speed versus ambient sound level together as if the same
processes governed both seasons,
2. Continues to reject Site 4 data because they are “too quiet.”

Consider winter. Mr. Hessler examines the ambient when the wind at 10 m is thought to be about 7 m/s and shows (Hessler’s BP winter study Figure 2.5.5) that about 80 % of the ambient data are louder than 37 dB with few data that are greatly quieter.1 This indicates that in winter when the winds (at 10 m) are about 7 m/s that the wind turbine can produce up to 43 dB at an affected property and be in compliance with the New York State guideline. But that is all it shows. It cannot necessarily be extrapolated to other wind speeds, and it definitely cannot be extrapolated to summer. Consider Figure 2.5.5 at 4 m/s. Here, about 80 % of the ambient data exceed 20 dB. So in winter, when the wind is 4 m/s, the turbine noise at an affected property must be less than 26 dB in order to comply with NYSDEC policy of 6 dB above background sound levels. Nowhere is this shown to be the case.

In summer, Hessler uses the winter ambient noise versus wind speed relation to predict the summer ambient even though, as Cavanaugh-Tocci has correctly noted, the summer data exhibit virtually no correlation between ambient sound level and wind speed. And, indeed, there is none. The summer data are dominated by insect noise, a high frequency noise that cannot and does not mask the lowfrequency wind-turbine noise. Even more importantly, regularly and frequently, especially at night, the relation between wind speed and altitude cited by Hessler breaks down completely. It is simply wrong.
 This is not some idle theory; it is a well known and well documented fact, and Hessler acknowledges this phenomena in his presentation (see quote below). What actually happens is that the wind is strong at hub height but it is calm near the ground (10 m). So the wind turbine can easily operate and make 1 Rightfully, Mr. Hessler chooses a wind speed and corresponding ambient sound level such that about 80% if the time the ambient is greater than 37 dB and 20% of the time it is quieter. This can be thought of as protecting 80% of the population or protecting 80% of the time, or some combination of these two. The important point is that the protection should be at least at the 80 to 90% level—not at 50%. noise while at the same time there is no masking wind noise at ground level.

How often does this condition occur? At the InterNoise2009 conference last August, the one Hessler mentions in his presentation, I chaired a session in which a paper was presented that contained factual data showing that this condition, strong winds at hub height and zero winds at 10 m, occurs almost every other night during the warmer weather months at Cape Vincent—almost every other night.

How loud is it? As Hessler stated during the recent hearing:

“Now turbine sound level varies with wind and weather conditions and time of day, no question about that. In particular, at night, wind tends to blow up above while calmer near the ground; the curvature of the shear profile is pretty slanted, so the top of the blades are in high wind and the bottom of the blades are in lower wind. That causes them to make a kind of churning noise, most often it happens at night. So, levels are going to vary, some time it's going to be completely naudible and other times temporarily rather loud, it's just the way wind turbines are.”

“Rather loud” means louder than predicted; louder than the “permitted” 43 dB(A). How much louder? The wind turbine manufacturers do not measure it—perhaps 5 to 10 dB.

What is the bottom line? During warm-weather months, almost every other night, the ambient, as we and Hessler both measured, will be about 25 dB(A). At the same time the wind turbine can be producing on the order of 50 dB. Rather than the permitted 6 dB increase, the true increase will be about 25 dB, and this huge increase may occur almost every other night.

People will be very unhappy—and rightfully so.

Paul Schomer, Ph.D., P.E.

Member, Board Certified, Institute of Noise Control Engineering

The original letter can be read at the end of this post
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Below is an additional letter from Dr. Paul Schomer to Supervisor Hirschey . This letter highlights  the inconsistencies concerning  the public release of  Hessler's  entire report .

Trannscript of the letter


Mr. Urban Hirschey – Supervisor
Town of Cape Vincent
1964 NYS Rte 12E
Cape Vincent, NY 13618
April 27, 2010

Dear supervisor Hirschey:

 Schomer and Associates, INC. Was called in May 2008 to study the ambient noise in the Cape Vincent area, in part, because BP consultant had produced a draft EIS 2007 that only utilized Hessler's summer measurements (Hessler report dated November 2007) and a "rule – of – thumb" estimate for winter attributed to Hessler (see for example tables on P .121 of the DEIS). The DEIS said there would be a "winter" study by Hessler that winter, only now know that Hessler completed this winter study in March 2008. Unfortunately, the public was never informed of the existence of this winter study for of its contents until shortly after the publication of our study late in 2008.

I have expressed my sympathy to George Hessler that his client withheld his winter study, creating at least in my mind, the impression that Hessler was advocating the use of insect – noise – corrupted data processing the BP project. In fact, if we had  had the Hessler winter study at the start of our study in may 2008, this would have significantly changed some of the focus and conclusions of our study. Insect noise would not have been the primary focus of our measurements. Thus, we would not have needed to place such an emphasis on showing how high the summer levels in the DEIS distorted the picture of the true, year – round ambient.

My sympathy to the withholding of the winter study does not mean I now agree all of the Hessler methods and conclusions. My letter of April 23, 2010 to you detail some of the major areas of disagreement.

Very sincerely,

Paul Schomer

Paul Schomer, PH. D., P. E.

Member, board-certified; Institute of Noise Control Engineering
~~~

  
DR. Schomer's April 23, 2010 letter to Supervisor Hirschey

DR. Schomer's April 23, 2010 letter to Supervisor Hirschey

Link here to read Schomers complete evaluation of Hesslers sound study for in Cape Vincent