• Smooth (laminar) air flow around blunt obstacles may result in the formation of vorticies (the plural of vortex) that snap off or shed with a characteristic frequency. This process is called vortex shedding and is another means by which sound waves are formed. This is how a whistle or flute produces sound. Aslo the aeolian harp effect of singing power lines and fluttering venetian blinds.

phhheeeeeeew

feeeeee

phweeeeeeeeeee

galway on flute, vivaldi's 4 seasons

i can hear it

even in a vacuum

(quote from physics.info)