Finding the Solid angle of a 3D Plot Group

Hello,

Recently im doing my final project for my undergraduate degree using comsol pressure acoustic, frequency domain to analyze the radiation pattern of loudspeaker driver in a vented enclosure.

I've already got the result that i want (3D Plot Group for the radiation pattern in certain frequencies), but now i want to extract or find the solid angle (in steradian) that created by the radiation pattern itself so i can measure it in my real loudspeaker. Could anybody please help me how do i find the solid angle (for example the red contour/the lobes) using comsol?

Here, i also attach my 3d plot group of my dodecahedron loudspeaker.

Thank you! i'm looking forward to your reply!