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also apply to schools, churches, medical services, and park areas. The nighttime standards differ from <br />the daytime standards only in areas intended for overnight sleeping. The NAC-1 daytime standards <br />apply during nighttime hours at other NAC-1 land-use areas not intended for overnight sleeping. The <br />NAC-2 standards are applicable to certain NAC-1 land uses if the following criteria are met <br />The building noise attenuation is at least 30 decibels (dBA); <br />The building has year-round, indoor climate control; <br />The building has no facilities for outdoor activities. <br />Table 1 <br />Minnesota State Noise Standards <br />Sound Level (dBA) <br />Noise Area General Land Day Night <br />Classification Use Type (0700-2200) (2200-0700) <br />L10 L50 L10 L50 <br />1 Residential 65 60 55 50 <br />2 Commercial 70 65 70 65 <br />3 Industrial 80 75 80 75 <br />2.2 Federal Noise Abatement Criteria <br />In the Federal Noise Abatement criteria, a noise impact is defined as occurring when the predicted <br />traffic noise levels: <br />■ Approach or exceed the noise abatement criteria (see Table 2); <br />■ Substantially exceed the e�sting noise levels.� <br />The Federal Noise Abatement Criteria (23 CFR, Procedures for Abatement of Highway Traffic Noise <br />and Construction Noise) are in terms of the Leq or L10 descriptor. In Minnesota, the L10 descriptor is <br />used to identify impacts and has been used to identify impacts in this analysis. The criteria for <br />activity category E(Table 2) are in terms of interior noise levels and are applied where there are no <br />exterior activities to be affected by traffic noise. All other criteria are in terms of exterior noise <br />levels. <br />The State of Minnesota has defined "approach or exceed" as being within one dBA or less of the <br />activity category of the NAC, and "substantially exceed" as an increase of five dBA or more over <br />e�sting noise levels. <br />i FHPM 7-7-3 Procedures for Abatement of Highway Traffic Noise and Construction Noise <br />[http://www.fhw a. dot. gov/legsregs/directive s/fapg/cfr0772.htm] <br />Noise Analysis RAMSP 105803 <br />TH 36 and Rice Street Interchange Page 3 <br />