This is a great little trick that you can easily whip out for comic relief next time your are sitting at a restaurant. The sounds produced range from a duck call to a flagulent.
This is a great sound production platform and yields well to modification. The possibilities are almost endless.
Step 1: Cut the Straw
Flatten an inch or so of the end of the straw and then cut the corners of the straw off starting about 1/2 inch from the end. The remaining flaps are the reeds that produce the sound.
The sound produced is affected by the shape and length of the reeds, so try cutting the corners off at different angles and starting at different lengths from the end of the straw.