Modelling propagation of sound wave by particle simulation
There is a huge body of research and commercial work on doing acoustic simulation. There are a two basic classes of simulation systems: 


Finite element or finite boundary: these model the actual physics by dividing air and or/surfaces into small patches and modelling step by step the interaction between the patches by locally solving the wave equations given the boundary and initial conditions of the patches near by
Approximation methods: Ray tracing, particle tracing, mirror image method, etc. These are macroscopic models that use certain simplifying assumptions such as specular reflections, simplified diffusion models, no diffraction, etc.  


This is a very complicated problem and it takes many person years to create a modelling system that actually produces useful results. There are commercial systems out there that you can buy. They vary greatly in complexity, capability, cost, and training required so it all depends on your specific application.