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SANTA ANA REZONE PROJECT <br />INITIAL STUDY/MITIGATED NEGATIVE DECLARATION <br />Environmental Issues <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 />Less than <br />Significant <br />Potentially <br />Impact with <br />Less than <br />Significant <br />Mitigation <br />Significant <br />Impact <br />Incorporated <br />Impact <br />❑ <br />❑ <br />No Impact <br />LE <br />❑ ❑ ® ❑ <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 />❑ ❑ <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 />City Council 22 — 90 3AM026 <br />Https://adecinnovations.sharepoint.cam/sites/PubIicationsSite/Shared Documents/Publications/Client(PN-JN)/0327/03270047/ISMND/03270047 Santa Ana Rezone Project ISM ND.docx <br />