How to we determine and abate noise levels for Category E (interior) activities?
If no exterior areas of frequent human use are present, then the NAC Category E activity should be considered. The method for measuring an interior noise level is to measure the exterior noise level and use Table 7 from our Highway Traffic Noise Analysis and Abatement policy to subtract from the exterior value and determine the interior noise level. Go to Page 10 of the actual document (or Page 14 of 71 in the Adobe Counter). FHWA considered sound insulation as an abatement option for public use or non-profit institutional structures, especially where there is no exterior area of frequent human use. FHWA is not allowed to consider sound insulation for residences, except in cases where a severe impact is identified.
