Beam angle is definitely a partial product of frequency...in that...generally..lower frequencies have wider beam angles than higher frequencies...

This is just general criteria of sound wave theory in that lower frequencies expand farther from the strong center emission point before their "ever-decreasing" strength gets to the -10db point...

What I was trying to stress is that the advertised beam angles of different brands cannot be used as a criteria "that this brand advertises wider beam angles at 83kHz than this brand does...yada yada.."

They measure them differently..

But in reality they both produce about the same beam angles at the same 83kHz frequency...
And they both produce about the same beam angles at 200kHz...

Rickie