|AASHTO R 20||Procedures for Measuring Highway Noise|
|AASHTO||AASHTO LRFD Bridge Design Specifications, Customary U.S. Units, 7th Edition, with 2015 Interim Revisions|
|FHWA Highway Noise Barrier Design Handbook|
NPCA's office will be closed on Thursday, Nov. 23 and Friday, Nov. 24, in observance of Thanksgiving. Regular business hours will resume on Monday, Nov. 27.