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3.0 ENVIRONMENTAL CHECKLIST <br />City of San Leandro 1388 Bancroft Avenue Project <br />November 2018 Initial Study/Mitigated Negative Declaration <br />3.0-55 <br /> <br />Potentially <br />Significant <br />Impact <br />Less Than <br />Significant <br />Impact with <br />Mitigation <br />Incorporated <br />Less Than <br />Significant <br />Impact <br />No <br />Impact <br />12. NOISE. Would the project: <br />a) The exposure of persons to, or the generation of, <br />noise levels in excess of standards established in <br />the local general plan or noise ordinance, or <br />applicable standards of other agencies? <br /> <br />b) The exposure of persons to or generation of <br />excessive groundborne vibration or groundborne <br />noise levels? <br /> <br />c) A substantial permanent increase in ambient noise <br />levels in the project vicinity above levels existing <br />without the project? <br /> <br />d) A substantial temporary or periodic increase in <br />ambient noise levels in the project vicinity above <br />levels existing without the project? <br /> <br />e) For a project located within an airport land use <br />plan or, where such a plan has not been adopted, <br />within 2 miles of a public airport or public use <br />airport, expose people residing or working in the <br />project area to excessive noise levels? <br /> <br />f) For a project within the vicinity of a private <br />airstrip, expose people residing or working in the <br />project area to excessive noise levels? <br /> <br />ENVIRONMENTAL SETTING <br />NOISE AND VIBRATION OVERVIEW <br />Noise is unwanted sound that disturbs human activity. Environmental noise levels typically <br />fluctuate over time, and different types of noise descriptors are used to account for this variability. <br />Noise level measurements include intensity, frequency, and duration, as well as time of <br />occurrence. Noise level (or volume) is generally measured in decibels (dB) using the A-weighted sound pressure level (dBA). There is a strong correlation between A-weighted sound levels and <br />the way the human ear perceives sound. All noise levels reported in this section are in terms of <br />dBA but may be expressed as dB, unless otherwise noted. <br />Because of the way the human ear works, a sound must be about 10 dBA greater than the reference sound to be judged twice as loud. In general, a 3 dBA change in community noise <br />levels is noticeable, while changes of 1–2 dBA generally are not perceived. <br />Noise levels typically attenuate (or drop off) at a rate of 6 dBA per doubling of distance from point sources near the ground. Noise levels may also be reduced by the introduction of intervening <br />structures.