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Munn&Perkins Quarry Excavation Permit ru • except in carefully controlled laboratory experiments, a change of 1 dB cannot be perceived; • outside of the Iaboratory,a 3 dB change is considered a just-perceivable difference; • a change in level of at least 5 dB is required before any noticeable change in human response would be expected; and • a 10 dB change is subjectively heard as approximately a doubling in loudness, and can cause adverse response These relationships occur in part due to the logarithmic nature of human hearing,as discussed previously. Because the decibel scale is based on logarithms;two noise sources do not combine in a simple additive fashion, rather logarithmically.For example,two noise sources of 50 dB combine to produce a total sound level of 53 dB,not 100 dB. Single-Event Noise Effects The following will address sleep disturbance or awakening of existing residents along East River Road by project asphalt haul trucks passbys(single events)during the project operating hours of 9 p.m. to 5 a.m. The project operating hours(9 p.m.to 5 a.m.)are considered nighttime hours for this project noise assessment;that is,it is expected that a majority of people could be sleeping during these hours. Project-related sleep disturbance will be addressed in terms of the American National Standard Institute, Inc. (ANSI)/Acoustical Society of America(ASA) S 12.9-2008 Part 6, Quantities and Procedures for Description and Measurement of Environmental Sound—Methods for Estimation of Awakenings Associated with Outdoor Noise Events Heard in Homes. Regulatory Setting 9 rY 9 State Regulations The State of California has guidelines for evaluating the compatibility of various land uses as a function of community noise exposure,as shown in Figure 3.4-3. The State of California also establishes noise exposure limits for vehicles licensed to operate on public roads. For heavy trucks, the state pass-by standard is consistent with the federal limit of 80 dB at a distance of 15 meters from the roadway centerline. The state pass-by standard for light trucks and passenger cars (less than 4.5 tons,gross vehicle rating)is also 80 dB at 15 meters from the roadway centerline.These standards are implemented through controls on vehicle manufacturers and by legal sanction of vehicle operators by state and local law enforcement officials. lift Munn&Perkins Quarry Excavation Permit 3.4-6 ESA 1211086 Draft ER April 2011