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2.1 The following chart provides a rough comparison of the noise levels of some common noise sources. Sound Pressure Level (dBAI Noise Source 140 130 120 110 100 90 80 70 60 50 40 ----------------------------- Jet Engine (at 25 meters) ------------------------ Jet Aircraft (at 100 meters) ----------------------------- Rock and Roll Concert ----------------------------- Pneumatic Chipper ------------- Jointer/Planer ----------------------------- Chainsaw ----------------------------- Heavy Truck Traffic ----------------------------- Business Office ------------------------ Conversational Speech ----------------------------- Library ----------------------------- Bedroom 30 ----------------------------- Secluded Woods 20 ----------------------------- Whisper Source: "A Guide to Noise Control in Minnesota," Minnesota Pollution Control Agency, httn://www.nca.state.mn.us/nrograms/nubs/noise.ndf and "Highway Traff'ic Noise," FHWA, httu://www.fhwa.dot.gov/environment/htnoise.htm State of Minnesota Noise Regulations In accordance with FHWA requirements, Mn/DOT has adopted a statewide noise policy that clarifies the FHWA terminologies of noise impacts. "Mn/DOT Noise Policy for Type I and Type II Federal- aid Projects as per 23 CFR 772" includes the following descriptions: Noise Level Approaching the NAC; Mn/DOT defines a level as "approaching" the criterion level when it is 1 dBA, or less, below the criterion leveL For example, 69 dBA is considered "approaching" the FHWA NAC category B level of 70 dBA. Substantial Increase in Noise; Mn/DOT defines a substantial increase in noise as those future predicted noise levels that exceed the FHWA NAC category B level of 70 by SdBA or greater, or 75dBA. Substantial Noise Reduction; Mn/DOT identifies feasibility requirements for the use of abatement procedures such as noise walls and their associated costs. These requirements require that every reasonable effort be made to obtain a substantial noise reduction. Mn/DOT defines a substantial noise reduction as SdBA or more from a noise impact. State noise standards are for a one-hour period and apply to outdoor areas. The standards are in terms of the L10 and L50 noise descriptors. The L10 is the sound level exceeded ten percent of the time, or six minutes out of an hour. The L50 is the sound level exceeded 50 percent of the time, or 30 minutes out of an hour. Table 1 provides the Minnesota State Noise Standards for three Noise Area Classifications (NAC), and for daytime, nighttime, L10, and L50. The standards for NAC-1 apply to residential areas and other uses intended for overnight sleeping (hotels, motels, mobile homes, etc.). The NAC-1 standards Noise Analysis RAMSP 105803 TH 36 and Rice Street Interchange Page 2