Editing Soundproofing (section)

====Noise barriers====
[[File:Shinkansen Noise barrier(concrete board standard type).jpg|thumb|Noise barrier alongside a railway line in Japan]]
{{Main|Noise barrier}}

Since the early 1970s, it has become common practice in the United States and other industrialized countries to engineer [[noise barrier]]s along major highways to protect adjacent residents from intruding [[roadway noise]]. The [[Federal Highway Administration]] (FHWA) in conjunction with State Highway Administration (SHA) adopted Federal Regulation (23 CFR 772) requiring each state to adopt their own policy in regards to abatement of highway traffic noise.<ref>{{Cite web|url=http://roads.maryland.gov/index.aspx?PageId=827&d=114|title=Sound Barriers Guidelines - Highway Traffic Noise|website=roads.maryland.gov|language=en|access-date=2017-07-10}}</ref> Engineering techniques have been developed to predict an effective geometry for the noise barrier design in a particular real-world situation. Noise barriers may be constructed of wood, [[masonry]], earth or a combination thereof.