Since detailed information on the calculation of the Insertion Loss of a single barrier (indoors
and outdoors) is available in the literature (Bies and Hansen 1996, ISO 9613-2, ISO 10847,
ISO 11821) this clause is concerned with the basic rules for the use of indoor barriers.
Barriers are placed between a noise source and a receiver as a means of reducing the direct
sound observed by the receiver. In rooms, barriers suitably treated with sound-absorbing
material may also slightly attenuate reverberant sound field levels by increasing the overall room
absorption.
Barriers are a form of partial enclosure usually intended to reduce the direct sound field
radiated in one direction only. For non-porous barriers having sufficient surface density, the
sound reaching the receiver will be entirely due to diffraction around the barrier boundaries.
Now we will consider the effect of placing a barrier in a room where the reverberant sound
field and reflections from other surfaces cannot be ignored.