Adaptive pyramid tracing: a new technique for room acoustics

A numerical code for the prediction of 3D sound propagation is presented. It is mainly suited for indoor environments, and uses a variation of the Pyramid Tracing Method, which we called Adaptive Pyramid Tracing. Energy carriers are three-sided pyramidal beams, which are adaptively split at each reflection according to impinged geometry. To avoid an exponential growth of the number of pyramids with the number of reflections, beams that have locally lower energy are absorbed by adjacent ones, in order to reduce their number without affecting the overall energy balance. Sound sources can be discretized with a user-defined number of pyramids and may have an arbitrary directivity pattern. Compared to a classical pyramid tracing the algorithm avoids receiver detection errors, energy losses, and consequently it does not require an (additive or multiplicative) correction factor to adjust the results. The code has been validated with numerical tests in order to verify both stability and agreement with current analytical methods, and finally with data measured in a real environment.