MEMO: Turbine noise predictions when adjusted to meet an LMAX compliance standard
Ken Kaliski of RSG and Richard Lampeter of Epsilon Associates|December 22, 2016
This important memo prepared by acosticians, Ken Kaliski of RSG and Richard Lampeter of Epsilon Associates, explains how using shorter averaging times, including a 10-minute Leq and a maximum instantaneous sound level (Lmax) would change the results of the modeled predictions. Mr. Kaliski and Mr. Lampeter state that, based on tests in Massechusetts, the maximum (Lmax) values would range from 6 dB to 11 dB greater than the hourly averaged values. A portion of the memo is provided below. The full memo can be downloaded from this page.
This important memo prepared by acosticians, Ken Kaliski of RSG and Richard Lampeter of Epsilon Associates, explains how using shorter averaging times, including a 10-minute Leq and a maximum instantaneous sound level (Lmax) would change the results of the modeled predictions. Mr. Kaliski and Mr. Lampeter state that, based on tests in Massechusetts, the maximum (Lmax) values would range from 6 dB to 11 dB greater than the hourly averaged values. A portion of the memo is provided below. The full memo can be downloaded from this page.
MEMO
TO: Ryan Pumford, NextEra Energy Resources, LLC
FROM: Ken Kaliski, P.E., INCE Bd. Cert., RSG
Richard Lampeter, Epsilon Associates
DATE: December 22, 2016
SUBJECT: Tuscola III modeling of Lmax and 10-minute Leq
The Almer Township ordinance does not specify a metric or averaging time for the wind turbine sound level limit. In our modeling submitted as part of Tuscola Wind III’s permit application, we assumed a one-hour equivalent average sound level (Leq), as this represents a relatively short-duration exposure, and can be predicted with a high degree of confidence using manufacturer sound power data (which is an Leq) and the ISO 9613-2 model with appropriate adjustments.
We understand that at the last Planning Commission meeting regarding Tuscola Wind III’s permit application, there were discussions about using shorter averaging times, including a 10-minute Leq and a maximum instantaneous sound level (Lmax). This memo outlines our modeling of these metrics.
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Based on the factors listed above, it is very difficult to quantify the additional adjustment necessary to conduct a modeling study of Lmax for a wind energy project. This necessitates the addition of a highly conservative adjustment factor to estimate an operational Lmax. The MassCEC study, depending on what table is viewed and other post-construction measurements, ranges LFmax2 values from about 6 dB to 11 dB greater than the Leq, although some degree of background contamination is included in those Lmax values. For this study, to be conservative, we are using an additional 11 dB adjustment above the +2.0 dB already modeled.
