Hornbostel - Sachs
(Single) flutes with internal duct
The air itself is the vibrator in the primary sense. The standing waves are significantly confined within the instrument itself. A narrow duct directs the air stream against the sharp edge of a lateral orifice. The duct is inside the tube. The lower end of the tube is a natural node of the pipe pierced by a small hole. India and Indonesia.
Partly-stopped flutes with internal duct