A Rattle Against Invasion

From: Detective
Description: I remember that my granny used to drive frogs away with a rattle, which makes a sound that resembles croaking. It worked flawlessly. Let’s find a rattle and clear the City of these slippery frogs.
Completed: My granny had exactly the same rattle. She went around her farm with it and "croaked" for hours. I’m sure that if it worked on the farm, it will work for us as well.