Just a note about those canisters: I wiped my save and did them, confirming each one and they were STILL hard to hear, no matter how many times I went over the spot or how high my tv volume was. (imagine a wii version where the sound comes from the wiimote speaker).
I once spent 10 minutes on a single canister before I heard it's chime. Other I would hear, but not realize they were in a shack, building, or water tower.
Moral of the story: You may THINK you cleared it before, but you can always be wrong.
As far as jump challenges go, I always found them hard to see in day OR night, and on top of that, they only appear when you get near them. Keep hustlin' and you'll activate it.