Discussion Forum

To investigate pressure amplitudes of ultrasound (f=2 MHz) scattered back from a water-filled balloon in an unlimited water space, I built a simulation model with the Ray Acoustics physics node (see attachment). The balloon (∅ 18 cm) has a wall that partly transmits and partly diffusely reflects.
As a source I defined a circular region on the boundary of the unlimited water space ('inlet') that releases rays in a forward cone head-on with the balloon. To detect back-scattered sound on this inlet, I defined a receiver ('nonlocal accumulator') on this same region. Although carefully converting definitions and studies of the "small concert hall" example from the application model library and varying mesh detail or ray release conditions, I cannot get any credible/reliable physical results for this problem.
Particularly, the "Ray Trajectories" graph confuses me as the trajectories (for which I assigned 100% reflectivity on the balloon wall) are displayed passing straight through the balloon. Also I am worried by the trajectory lines seeming to reflect at random positions that do not intersect with the balloon wall. Concerning the parametric sweep of transparency values, I am not feeling well about the pressure amplitudes in the "Received acoustic pressure for different transparency" graph: for a transparency of 100% I do not expect any received pressure amplitude on the receiver but the simulation still gives a few pascals.
Because I am out of ideas to debug this model and the Acoustics Module user guide does not give any clues either, I am hoping for some expert help of other users. Many thanks in advance!