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Environmental Checklist Noise <br /> Initial Study – Mitigated Negative Declaration 65 <br />12 Noise <br /> <br />Potentially <br />Significant <br />Impact <br />Less than <br />Significant <br />with <br />Mitigation <br />Incorporated <br />Less than <br />Significant <br />Impact No Impact <br />Would the project result in: <br />a. Exposure of persons to or generation of <br />noise levels in excess of standards <br />established in the local general plan or <br />noise ordinance, or applicable standards <br />of other agencies? □ □ ■ □ <br />b. Exposure of persons to or generation of <br />excessive groundborne vibration or <br />groundborne noise levels? □ □ ■ □ <br />c. A substantial permanent increase in <br />ambient noise levels above those existing <br />prior to implementation of the project? □ □ ■ □ <br />d. A substantial temporary or periodic <br />increase in ambient noise levels in the <br />project vicinity above levels existing <br />without the project? □ □ ■ □ <br />e. For a project located in an airport land <br />use plan or, where such a plan has not <br />been adopted, within two miles of a <br />public airport or public use airport, would <br />the project expose people residing or <br />working in the project area to excessive <br />noise levels? □ □ □ ■ <br />f. For a project near a private airstrip, <br />would it expose people residing or <br />working in the project area to excessive <br />noise? □ □ □ ■ <br />Fundamentals of Noise <br />Noise is unwanted sound that disturbs human activity. Environmental noise levels typically fluctuate <br />over time, and different types of noise descriptors are used to account for this variability. Noise <br />level measurements include intensity, frequency, and duration, as well as time of occurrence. Noise <br />level (or volume) is generally measured in decibels (dB) using the A-weighted sound pressure level <br />(dBA). Because of the way the human ear works, a sound must be about 10 dBA greater than the <br />reference sound to be judged as twice as loud. In general, a 3 dBA change in community noise levels <br />is noticeable, while 1-2 dBA changes generally are not perceived. Quiet suburban areas typically <br />362