I mounted an ancient horn driver in a board, fed it from an ancient
Heathkit audio generator, placed a glass close to the hole, and
measured the decibels on the far side of the glass.
Then I cut the bell off a toy bugle I found at a yard sale for $1.00,
inserted it into the driver. and remeasured the sound level.
I have pictures of the before and after setups.
With the horn, I measured about 18 db louder.
Someone remind me how to post pictures without overloading anyones equipment.
--
Clarence Bennett
Oakland University
Dept. of Physics, (retired)
111 Hannah
Rochester MI 48309
248 370 3418