Hornbostel - Sachs
(Single) flutes with external 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 outside the wall of the flute; this group includes flutes with the duct chamfered in the wall under a ring-like sleeve and other similar arrangements. The lower end of the flute is closed.
Stopped flutes with external duct