I printed it at 100% size with 0.4mm nozzle,1.2mm shell 0.1mm layer height using ABS on a Monoprice Mini Delta without problem. I used 40% infill and the whistle feels VERY solid - 100% might be overkill. Make sure you have "support material"/"support type" set either to NONE or TOUCHING BUILDPOINT only.
If lowering the infill doesn't fix it, you might print it a little oversized (110%) and see if that helps. Somewhat larger size would lower the pitch somewhat, but should not affect the volume.