MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
That means there's holes. As a test, try painting (acrylic paint works fine) the whistle on the bottom and/or top to see where the holes are and re-slice to get a fully sealed print. I frequently get micro-holes on the bottom of the whistle if the bed isn't exactly perfect, but painting the bottom fixes it.