When I was a kid we used to make these whistles out of jam tin lids.
Apart from being a fun toy for kids, I think these whistles would be great working with dogs, directing cranes, or even to attract attention in an emergency. They are pretty loud and you don't have stick your fingers in your mouth - this can be a pain if you happen to be wearing gloves or your hands are dirty.
I have heard that similar whistles are popular with shepherds in New Zealand who use them for directing their dogs.
Step 1: What You Will Need
1 lid from a tin can
A drill with a bit about 3mm
hammer and centre punch
A small piece of ply or something to bend the tin around. About 4mm thick.
A knife for cutting the duct tape.
Step 2: Make the Tin Safe
Step 3: Make Your Whistle
Clean up any sharp bits from around the hole, and that's it.
Just look at the video to see how easy it is.
Step 4: How to Make It Whistle
Place the folded part of the whistler against the bottom of your tongue.
Push your tongue back with the whistle so the tip of your tongue points at the roof of your mouth.
Let you lips gently seal against the top and bottom part of the whistle.
Blow soft and hard and experiment with different mouth shapes until your make it whistle.
It might take a bit of practice to get started, but before long you will notice dogs and cranes desperately trying to follow your instructions.