TRPA uses a Community Noise Equivalent Level (CNEL) meaure to assess whether noise levels are being exceeded in Plan Areas. The CNEL averages decible levels over a 24 hour period, with excess noise late at night and early in the morning being weighted greater due to humans and wildlife being more sensitive to noise at these times. Noise monitors are generally put out in Plan Areas for 1-2 weeks during peak noise periods (generally summer). The average 24-hour CNEL measured is used to assess noise levels. Construction noise or other unusual noise events are excluded from the data. Noise monitors are calibrated and tested to noise industry standards to ensure proper measurements. TRPA monitors 35 Plan Areas per year, and re-visits each site once every 4 years (140 Plan Areas monitored total). 

In general, the following CNEL noise levels are allowed in different land use categroies: 

• Wilderness and roadless areas = 45 dB
• Low density residential areas = 50 dB
• Rural outdoor recreation areas = 50 dB
• High density residential areas = 55 dB
• Urban outdoor recreation areas = 55 dB
• Commercial areas = 60 dB
• Hotel / motel areas = 60 dB
• Industrial areas = 65 dB