Baseline Noise Study for Residents for Sound Economics and Planning, Ubly, Michigan 

This report presents the findings and recommendations from a study conducted to determine Community Response and Land Use Compatibility of the Noble Thumb Windpark. Data for this study was collected from three properties located near Ubly, Bingham Township, Huron County, Michigan. The study evaluated the Land Use Compatibility and Community Response to the changes that would occur in the Ubly and Bingham Township soundscape after installation of industrial scale wind turbines by Noble Environmental Power LLC. …

The sound levels and procedures in the State and Huron County documents are seriously flawed. They do not follow the recommendations of the Lawrence Tech study group nor do they follow generally accepted methods used by acoustical experts. The upper bounds of acceptable sound levels from the turbines are set extremely high and standard acoustical definitions are altered to make it easier to meet the sound level requirements. But, as a gauge of how lenient the guidelines in the Michigan and Huron County ordinance are with respect to sound emissions, if the full latitude permitted in the ordinance was used by the proposed Windpark, the soundscape in Ubly and the adjacent areas of Bingham Township would be noisier than most dense urban communities at night. Considering that Bingham Township and much of Huron County is rural these guidelines are inappropriate in that they do not account for the quieter background soundscape in rural areas nor do they account for the “…. greater expectation for and value placed on “peace and quiet” in quiet rural settings. In quiet rural areas, this greater expectation for “peace and quiet” may be equivalent to up to 10 dB.” …

The study found that the existing background (ambient) sound levels (L90) at all three sites were significantly lower than the sound levels reported in the Noble Study. …

The sounds of the turbines, at locations where they are louder than the naturally occurring sounds, will become the dominant sound in the soundscape during the times when sounds of vehicles and other sources of short term sounds are not present. …

The findings of this study showing daytime and evening ambient sound levels in the 31 to 33 dBA range and nighttime levels in the 23 to 29 dBA range are at variance with the sound levels reported as the existing sound levels in Bingham township area by Noble. Noble’s study (Tables 3 and 4 included in attachment) shows daytime sound levels at sites deemed to be noise sensitive ranging from the low 40’s to mid 50’s (dBA (Leq)). Night time sound levels are shown as being in the low 30’s to mid 40’s (dBA (Leq)). One explanation for this difference is that the Noble study was reporting average sound levels (Leq) which included the effects of transient sounds and not the ambient background (L90) sounds as would be used in studies that comply with recent versions of ANSI and ISO standards. This difference is significant in that it permitted Noble to draw the conclusion that noise would not be a significant issue when the turbines are installed. …

Using Noble’s predicted average sound levels the introduction of the turbines will increase ambient sound levels by 10-15 dBA or more for residents close to town or main roads (Sites 1 and 2) during the evening and night time; and 15-20+ dBA or more for the residents who are in the more rural areas (Site 3). Since the current regulation permits sound levels of 50 dBA and the predicted sound levels in Noble’s study are for a 1.5 MW turbine there is nothing in the current regulation that would prevent Noble from installing larger turbines and bump the sound emissions up to the 50 dBA limit. Noble’s assertion that the turbine sounds may be at least partially masked by wind noise are true. But it is not true for low wind speeds or when high wind gradients are present. The data collected for this study was during wind conditions of 3-9 mph. So the rustling of leaves, etc. that would mask the WTG was included in the samples. According to several sources, surface winds of 3-9 mph would have been sufficient to power the WTG’s because the wind speed increases considerably at the height of the hub and blades over what is measured on the ground. This is truer at night when winds tend to decrease considerably at ground level, but remain adequate at the blade height to power the turbines. There is also a condition that occurs when temperatures at the ground level are different from the temperature at the hub/blade height where the sounds of the turbine and its blades are directed downward toward the ground. This condition would make the sound levels at the residence higher than Noble’s predicted values. Nighttime levels in the homes are expected to be in the low to mid 20 dBA range based on the tests conducted inside the residences of the study participants. The turbines would set the outdoor background sound levels approximately 20 dB higher (steady sound of 40-45 dBA) than the naturally occurring nighttime sounds and thus could cause sleep interference. This would be especially true for people who leave windows open in the evening and nighttime. …

Recommendations 1. The sound level limits given in the Huron County Ordinance should be reconsidered in light of the incorrect use of sound level descriptors and limits. The day and night time limits should be based upon an independent study of the ambient background sound levels in the community and not upon an arbitrary level such as the 50 dBA level provided in the Ordinance. a. the regulation be changed to read that the turbines cannot exceed the ambient sound level (L90) plus 5 dBA or 50 dB whichever is less, during the evening and night hours. This limit would apply to any operating or weather condition at the nearest non-lessee property line. …

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