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ͭͲͱͱʹ-ͬͰ Noise Memo.docx ͳ Warner Avenue Footlab TABLE 1: REFERENCE OPERATIONAL NOISE LEVELS Noise Source1 Noise Source Height (Feet) Min./ Hour2 Reference Noise Level (dBA Leq) @ 50 Feet Sound Power Level (dBA)3 Day Night Loading Activity 8' 60 0 72.1 103.7 Roof-Top Air Conditioning Units 5' 39 28 57.2 88.8 Trash Enclosure Activity 5' 10 0 57.4 89.0 Parking Lot Vehicle Movements 5' 60 0 49.5 81.1 Soccer Games 5' 60 0 58.4 90.0 1 As measured by Urban Crossroads, Inc. 2 Anticipated duration (minutes within the hour) of noise activity during typical hourly conditions expected at the Project site. "Daytime" = 7:00 a.m. - 10:00 p.m.; "Nighttime" = 10:00 p.m. - 7:00 a.m. 3 Sound power level represents the total amount of acoustical energy (noise level) produced by a sound source independent of distance or surroundings. Sound power levels calculated using the CadnaA noise model at the reference distance to the noise source. CADNAA NOISE PREDICTION MODEL To fully describe the exterior operational noise levels from the Project, Urban Crossroads, Inc. developed a noise prediction model using the CadnaA (Computer Aided Noise Abatement) computer program. CadnaA can analyze multiple types of noise sources using the spatially accurate Project site plan, georeferenced Nearmap aerial imagery, topography, buildings, and barriers in its calculations to predict outdoor noise levels. Using the ISO 9613-2 protocol, CadnaA will calculate the distance from each noise source to the noise receiver locations, using the ground absorption, distance, and barrier/building attenuation inputs to provide a summary of the noise level at each receiver and the partial noise level contributions by noise source. Consistent with the ISO 9613-2 protocol, the CadnaA noise prediction model relies on the reference sound power level (Lw) to describe individual noise sources. While sound pressure levels (e.g., Leq) quantify in decibels the intensity of given sound sources at a reference distance, sound power levels (Lw) are connected to the sound source and are independent of distance. Sound pressure levels vary substantially with distance from the source and diminish because of intervening obstacles and barriers, air absorption, wind, and other factors. Sound power is the acoustical energy emitted by the sound source and is an absolute value that is not affected by the environment. The operational noise level calculations provided in this noise study account for the distance attenuation provided due to geometric spreading, when sound from a localized stationary source (i.e., a point source) propagates uniformly outward in a spherical pattern. A default ground attenuation factor of 0.5 was used in the noise analysis to account for mixed ground representing a combination of hard and soft surfaces. Appendix B includes the detailed noise dBA Leq model inputs used to estimate the Project operational noise levels presented in this section.