Sources étendues (sources linéiques et surfaciques)

At calculation time, extended sources (line and area sources) are represented by a set of incoherent point-sources. The density of these point sources is adapted to balance accuracy and efficiency.

In particular, a higher density is used for portions of an extended source that are near the receiver. Also, when an extended source is partly behind an obstacle (partly invisible to the receiver), this density is increased in the transition from being invisible to being visible (as the contribution is likely to vary considerably in such a transition zone). This is a form of adaptive sampling; its effect on accuracy is similar to that of the additional subdivision using the projection method (see ISO-9613).

For efficiency, the adaptability of sampling density near obstacle edges is applied only for sources within 1000m from the receiver (where most accuracy is needed).