ANSI/ASA S12.8-1998 (R2003)

This standard presents three methods for determining the insertion loss of outdoor noise barriers. The methods are direct BEFORE and AFTER measurements; indirect BEFORE measurements at an equivalent site; and indirect predictions of BEFORE sound levels. Indirect BEFORE measurements and indirect BEFORE prediction methods require direct measurements of AFTER sound levels. Measurements of acoustical descriptors use sound sources naturally present at a site, controlled natural sound sources, or controlled artificial sound sources. Within prescribed limits, the receiver location and atmospheric, ground, and terrain conditions may be chosen based on the objectives for determination of barrier insertion loss. Examples are provided for worksheets that may be used for data acquisition and analysis.