I was just looing at the calculator that
@sarumbear provided, and realized the diffraction effects I mentioned earlier are built into the
calculator. I put in 20kHz as the upper frequency for the panel and the calculator returned 0.86cm square elements (exactly half the wavelength of 20kHz sound in air at Standard Temperature and Pressure!!!)
View attachment 242082
So above 20kHz this panel will start beaming. Faceting would help, or just making the columns smaller cross section to get to successively higher frequencies. (Or just having my hearing!
) Also, the lower frequency determine the height of the column elements, 2kHz give 8.6cm long columns. Very nice! Hope this helps.