David, I talked with Ed Couch this morning and asked him to come back to our thread.............he said he would be glad to.......He said that there is a sound module that will replicate the Radial engine........I think he said it can also reproduce the sound of twins........he said it was loud enough to be heard in flight..........I built a Dumas 1930 Chris Craft triple cockpit runabout back in 1994..........it was electric powered, but did not sound anything like the original Grey Marine engine with duel exhaust..........But, I discovered that even way back then the engine sound module was available...........the one I purchased and installed could be programmed to sound like a diesel or gas engine......it came with a small radio speaker which worked well up close.......but could not be heard from a distance......Ed said they do not use the ole style paper coned speaker like I had on the boat twenty years ago.......it is far better.........so, stay tuned, ......Ed said he can satisfy your brain's desire for the electric and your heart pounding love of those beautiful Jacobs raspy sound.........Rich.