1. A method for simulating sound propagation, the method comprising: defining a sound source position within a modeled scene having a given geometry; constructing a visibility tree for modeling sound propagation paths within the scene; using a from-region visibility technique to model sound diffraction within the scene and reduce the size of the visibility tree; using a from-point visibility technique to model specular sound reflections within the scene and reduce the size of the visibility tree; using the visibility tree to generate an impulse response for the scene; and using the impulse response to simulate sound propagation in the scene.