Noise Testing–Do it Right

The residents of Kingston and Fairhaven who have complained about noise have some reason to expect testing to vindicate their experience. According to Alicia McDevitt, who just left the MassDEP to become head of the MassCEC, if there are a lot of complaints, the noise source usually exceeds the 10 dB(A) limit (comments at the Wind Working Group presentation on July 18, 2012).

However, in a post comment by Chris Kapsambelis, he warns that residents

need to take note of the fact that the MassCEC Acoustic Study Methodology for Wind Turbine Projects does not use the absolute maximum metric Lmax to determine compliance. It continues to use the L90 metric which was used by the developer in Falmouth to initially declare Wind-1 in compliance. Since then the MassDEP has rejected this approach in favor of the Lmax metric which was used to find Wind-1 out of compliance at night.

The MassDEP instructions for taking field “background” readings is “Take an instantaneous reading every 10 seconds until you have 100 readings.  The 10^th lowest reading is the ‘background’ level” (i.e. the “L90” level, the level which is exceeded 90% of the time.” (MassDEP Guidance, 2003, p. 12).

In Acoustics and Wind Turbine Noise Chris explains the issues involved in noise testing as well as the consistent track record of the DEP–using the maximum volume of noise from wind turbines for compliance testing protocols.