As I known that size of magnetic buzzers always rated a effective frequency to make louder sound. So I tested it on DEVO10 by editing \media\sound.ini to load a continued scale of sound to listen to it and I found it is frequency sensitive.
In my DEVO10, C & D scale always louder than others especially C3 and D3.
I measured the frequency by an App to get 1743Hz of C3 sound on my DEVO10, that is less than A scale a bit, don't know how it comes but it really work fine for me.
Made a louder version of sound.ini that you can try it out.
One thing about volume is that volume=0 don't turn off the buzzer when Tx start up, also volume=1 sound the same like volume=10.
