I grew up watching Richard Greene every week in "The Adventures of Robin Hood"..... yes, I am that old. When ever it was necessary to deliver a message in the forest, it was often attached to an arrow and the arrow would whistle while in flight (isn't Hollywood wonderful).
Then a couple of days ago I was visiting one of the other archery boards and noticed a posting concerning "whistling arrows" that had been made with a ping pong ball at the front of the arrow. What the heck, ping pong balls are dirt cheap so decided to give it a try... the worst that could happen is that it wouldn't work and I would be out a buck and a half for a half dozen ping pong balls.
The general idea was to cut 3 or 4 triangular holes in the ball with the base of the triangles being aligned along the seam line of the ball, the point ont he triangle being faced towards what would be the point of the arrow. Two small holes are then cut in the ball for the arrow to pass through.
Believe it or not, this actually works. The arrow whistled quite loudly while in flight !!!! I'd expected the ping pong ball to shatter when the arrow struck the woven mat target, but it just slid back along the arrow shaft none the worse for wear. Managed to get 8 shots out of the same ball before it started to crack and break.
Haven't really had a chance to play with this much yet, but so far the larger the holes the louder the whistling sound. Can't say as it does a thing for enhancing accuracy, but it sure as heck is fun to play with.