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SANTA ANA REZONE PROJECT <br /> INITIAL STUDYIMITIGATED NEGATIVE DECLARATION <br /> Less than <br /> Significant <br /> Potentially Impact with Less than <br /> Significant Mitigation Significant <br /> Environmental Issues Impact Incorporated Impact No Impact <br /> 2.13 Noise <br /> Would the project result in: <br /> a) Generation of a substantial temporary or ❑ ❑ ® ❑ <br /> permanent increase in ambient noise <br /> levels in the vicinity of the project in excess <br /> of standards established in the local <br /> general plan or noise ordinance, or <br /> applicable standards of other agencies? <br /> b) Generation of excessive groundborne ❑ ❑ ❑ <br /> vibration or groundborne noise levels? <br /> c) For a project located within the vicinity of a ❑ ❑ ❑ <br /> private airstrip or an airport land use plan <br /> or, where such a plan has not been <br /> adopted,within two miles of a public airport <br /> or public use airport, would the project <br /> expose people residing or working in the <br /> project area to excessive noise levels? <br /> Setting <br /> Characteristics of Noise and Vibration <br /> Noise is defined as unwanted sound. Sound levels are usually measured and expressed in decibels <br /> (dB), with 0 dB corresponding roughly to the threshold of hearing. Most of the sounds that we hear in <br /> the environment do not consist of a single frequency, but rather a broad band of frequencies,with <br /> each frequency differing in sound level. The intensities of each frequency add together to generate a <br /> sound. Noise is typically generated by transportation, specific land uses, and ongoing human activity. <br /> The standard unit of measurement of the loudness of sound is the dB. The 0 point on the dB scale is <br /> based on the lowest sound level that the healthy, unimpaired human ear can detect. Changes of 3 dB <br /> or less are only perceptible in laboratory environments.A change of 3 dB is the lowest change that <br /> can be perceptible to the human ear in outdoor environments. While a change of 5 A-weighted <br /> decibel (dBA) is considered to be the minimum readily perceptible change to the human ear in <br /> outdoor environments. <br /> Since the human ear is not equally sensitive to sound at all frequencies, the dBA scale was derived to <br /> relate noise to the sensitivity of humans. It gives greater weight to the frequencies of sound to which <br /> 76 FCS <br /> Ordinance No. Nor`s=,atlons.sharepoint.mmfsires/Pu6[icatiunsSite/shared Documents/Puhlirat€nosUenk(PN-sNl1032 7/03 7 7o 7/ISMND/0327IX 7 Santa Ana RezoneProledWANDA— <br /> Page 88 of 118 <br />