When I was young, my father made that for me. It was maybe 30 years ago ;)
It is very noisy and easy to make. Youngsters find that very entertaining ;)
You just need a sheet of paper, scissors, tape and a few minutes. Then you have to moderately aspirate thought the paper honk and you'll get that specific noise. It makes me think of a goose, or a duck...
Step 1: Gather the Material
Take a sheet of paper, a pen (or anything tubular), tape and scissors.
Step 2: Roll the Paper
Use the pen to roll the sheet of paper following the diagonal.
Tape the sheet. I used blue tape because the clear tape is not as easy to see on a photo ;)
Remove the pen.
Step 3: Cut the Tube
Cut the tube on each side with a straight cut.
Step 4: Cut the Reed
At one end make an oblique cut (ok, you could have done that at the previous step instead of a straight cut).
Then, do an incomplete straight cut and cut the resulting cone inside to have some triangles.You'll get several layers.
Step 5: Prepare the Reed
Once you have the reeds, remove incomplete ones to get one complete wich can cover the tube.
Bent it up, the others stay down.
Give it a try and slightly aspirate thought the other side of the tube, you should get some honk.
If you aspirate too strong, the reed stucks on the tube and it do not vibrate.
Step 6: Tune the Tone
You can change the tone, from a low-pitched sound to one sharper, cutting the reed.
You can cut every vertices of the triangle, or one, to modulate the sound.
If you cut too much, remove the damaged reed and replace it with the following.
Step 7: Video How-to
I've made a quick video (env 1min30) which should make things clear.
Have a look at it, and let me know if anything is unclear ;)