I have printed this 4 times now, and unfortunately I still cant get it to whistle. It is just air that comes out the sides.
Black PLA (110C - 120C varies)
Both 0.2 and 0.1mm resolution
100% infill always
No supports or rafts
Prints were pretty good quality and did not have any "stringers" and only a few distortions
Using Prusa I3
I believe it may be due to the print being slightly porous (maybe the air is escaping elsewhere). I have seen a lot of the 91 made ones being worse quality than the ones I made however.