Measured C-Weighted Ambient Sound Levels for Use with Environmental Noise Regulations in Alberta

Résumé

Noise Impact Assessments (NIAs) for industrial facilities in Alberta are typically conducted in accordance with Alberta Utilities Commission (AUC) Rule 012 or Alberta Energy Regulator (AER) Directive 038. Both regulations assess noise cumulatively and require that the contribution of natural and non-industrial sources be included when testing noise compliance for industrial facilities. Both regulations require that A-weighted and C-weighted cumulative noise levels be compared; a difference between C-weighted and A-weighted noise levels greater than or equal to 20 is considered indicative of a potential Low Frequency Noise (LFN) issue. Both regulations provide desktop techniques for estimating the A-weighted Ambient Sound Level (ASL) associated with natural and non-industrial noise sources based on population density and proximity to transportation infrastructure. The problem is that neither regulation outlines a methodology for estimating C-weighted ASL values.  As such, it is difficult to apply the LFN test using cumulative noise levels and instead NIAs often consider a facility in isolation when testing for LFN issues. This can lead to potential LFN issues being identified even when facility noise levels are very low – so low that they would be completely obscured by the background ASL if it could be included in the LFN test. This paper establishes a link between A-weighted and C-weighted ASL values for three types of noise receptors: remote areas far from human activity, rural farmhouses, and dwellings adjacent to noisy highways. C-weighted ASL values that can be used in conjunction with the A-weighted ASL values when applying regulatory LFN tests are presented. Links between A-weighted and C-weighted ASL values are established by examining measured noise spectra from approximately 15 receptor locations.