This document is a guide to specifying construction details that have been shown to provide enhanced levels of sound insulation. Since 1966, there has been an increase in noise producing devices available to domestic users. This guide attempts to bring together the information on masonry construction and framed construction, including new research on timber floors. But good levels of sound insulation also depend on workmanship on-site. Advice on achieving this can be found in the companion document, BR358 Quiet homes, a guide to good practice and reducing the risk of poor sound insulation between dwellings. 51 pages.