This past summer I decided to finally teach myself to whistle. Having finally succeed in whistling successfully, I thought I would comment briefly on it. I actually found two different kinds of whistling, normal and lateral. I never figured out how to whistle inward like many people, but I haven’t seen anyone do a lateral whistle before. In the lateral whistle, the lips are pursed in an under bite, as if playing the panpipes and the tongue is close to the roof of the mouth and to one side, as if pronouncing an “l”. I’d always tried whistling from the panpipe position because I learned the lip position for them before I learned to whistle.
I was able to listen normally also. The key was having the tongue on the upper portion of the back of my teeth with lips pursed in an O. I’m still not sure how so many people seem to whistle without trying. Maybe it depends on mouth structure or the ability to curl the tongue (I can’t).