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Ldn. Ldn means the day -night average level, or the 24-hour equivalent <br />continuous sound level (time -averaged A -weighted sound level) from midnight to <br />midnight, obtained after the addition of 10 dBA to sound levels measured from <br />10 p.m. to 7 a.m. <br />NOISE REDUCTION LEVEL. Noise reduction level means the difference between the <br />exterior and interior sound level, expressed in dBA, which is achieved by the <br />intervening structure. <br />RECOGNIZED ACOUSTICAL SPECIALIST. A recognized acoustical specialist means a <br />person qualified by education and experience to conduct sound analysis of <br />buildings and approved for such purpose by the city's building inspector. The <br />approved individual shall have at least three years of experience in the field <br />of sound control; a degree from a recognized institute of higher learning in <br />acoustics or a closely related discipline; and demonstrated expertise in the <br />process of sound analysis of buildings. <br />SOUND. Sound means energy that is transmitted by pressure waves in the air <br />or in other materials and is the objective cause of the sensation of hearing. <br />It is commonly called noise if it is unwanted. <br />SOUND ATTENUATION. Sound attenuation means the reduction in sound level which <br />occurs between the source and receiver. <br />SOUND LEAK. Sound leak means an opening in a structure through which sound can <br />pass. Sound leaks are often extremely small holes or cracks. In general, an <br />air leak is a sound leak. <br />SOUND LEVEL. Sound level means the level of sound pressure measured with a <br />sound level meter and one of its weighting (frequency) networks. When A - <br />weighting is used, the sound level is expressed as dBA. <br />SOUND TRANSMISSION CLASS (STC). Sound transmission class means a single -number <br />rating for describing the degree of sound transmission loss specified for a <br />wall, window, partition or other building element. The higher the STC, the <br />more attenuation the building element will afford. <br />Section 5 Scope and Effect <br />The Aircraft Noise Zones established by this ordinance shall overlay the zoning <br />districts established by Ordinance No. adopted so that <br />any parcel of land lying in an overlay zone shall also lie in one or more of <br />the established zoning districts. Territory within a given overlay zone shall <br />be subject to the requirements established by the other applicable ordinances <br />and regulations of the city. Within each adopted overlay zone, all uses shall <br />be permitted in accordance with the regulations for the underlying zoning <br />districts, provided, however, that the appropriate building permit is first <br />obtained and provided further that no use designated as inconsistent on the <br />Noise Compatibility Tables, and incorporated herein, shall be permitted. This <br />ordinance applies to all construction requiring a building permit after the <br />effective date of this ordinance except decks, patios, swimming pools, <br />breezeways and similar outdoor uses and remodeling or rehabilitation of an <br />existing residential building, nor to the construction of an appurtenance to an <br />existing residential building. In the case of conflict between this ordinance <br />and any other applicable codes or ordinances, the more restrictive requirement <br />shall be met. <br />1 <br />27 <br />