…so, after a couple of years of trying to leave the idea aside, I finally bought a 3D printer.
I'm really amazing how good is a cheap printer (€217) nowadays, and how easy it was to set it up.
In the first concave prints I had lots of stringing, which I solved as suggested by CHEP
So, yes, now I own a 118dB whistle
and I don't even know why. :P
You can follow my experiments in this Google Photos album: