GROUND INFLUENCE ON THE DEFINITION OF SINGLE RATING INDEX FOR NOISE BARRIER PROTECTION

A single number rating index to qualify the acoustical protection of a noise barrier that accounts for the influence of the ground is develo ped. This is an extension of a previous index for semi-infinite barrie r developed by Pfretzschner [Pfretzschner et al., Acust. Acta Acust. 8 2, 504-508(1996)]. This index is based on the asymptotic value found f or the insertion loss or the acoustic attenuation as physical magnitud e, and it is uniquely dependent on the barrier, noise source, and acou stic characteristics of the ground in the source semi-space. The new i ndex agrees well with measured data on a scale model under laboratory conditions, and a direct experimental measuring procedure could be env isaged. In this way the proposed index, which accounts for extrinsic p roperties (acoustical protection) of barriers, would complete the two previous indices dealing with intrinsic properties (transmission loss and acoustical absorption). (C) 1998 Acoustical Society of America. [S 0001-4966(98)01807-4].