What about an audible one? A few years back, someone at our field taped on one of those plastic kid toy whistles (it was a hollow tube with a small plastic turbine shaped wheel inside). The whistle made a whirring sound that increased in pich the faster he went. In dives it sounded like a jet. The thing is called a "whizzer"

Here is a link:

http://www.oriental.com/webapp/comme...ispAll=&CASE=0