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Acoustical Analysis Report Griffith Energy Storage Project 6.0 OPERATIONAL NOISE This section describes the model utilized forth e assessment;input assumptions used to calculate noise levels due to the Project's normal operation;a conceptual noise mitigation strategy,and the results of the noise impact analysis. 6.1 Noise Prediction Model The Cadna-A°computer noise model was used to calculate sound pressure levels from the operation of the Project equipment in the vicinity of the Project site.An industry standard,Cadna-A°was developed by DataKustik GmbH to provide an estimate of sound levels at distances from sources of known emission. It is used by acousticians and acoustic engineers due to the capability to accurately describe noise emission and propagation from complex facilities consisting of various equipment types like the Project and in most cases,yields conservative results of operational noise levels in the surrounding community. The current ISO standard for outdoor sound propagation, ISO 9613 Part 2-"Attenuation of Sound during Propagation Outdoors,"was used within Cadna-A(ISO 1996).The method described in this standard calculates sound attenuation under weather conditions that are favorable for sound propagation,such as for downwind propagation or atmospheric inversion,conditions which are typically considered worst-case.The calculation of sound propagation from source to receiver locations consists of full octave band sound frequency algorithms,which incorporate the following physical effects: oo Geometric spreading wave divergence; oo Reflection from surfaces; oo Atmospheric absorption at 10 degrees Celsius and 70 percent relative humidity; oo Screening by topography and obstacles; oo The effects of terrain features including relative elevations of noise sources; oo Sound power levels from stationary and mobile sources; oo The locations of noise-sensitive land use types; 0o Intervening objects including buildings and barrier walls,to the extent included in the design; oo Ground effects due to areas of pavement and unpaved ground; oo Sound power at multiple frequencies; oo Source directivity factors; oo Multiple noise sources and source type (point,area,and/or line);and oo Averaging predicted sound levels over a given time. Cadna-A allows for three basic types of sound sources to be introduced into the model: point, line, and area sources. Each noise-radiating element was modeled based on its noise emission pattern. Larger dimensional sources such as the transformers were modeled as area sources. OTETRA TECH 13 August 2023