Just wanted to mention this, the music on my game was messed up, so I play with my Music Volume all the way down.
By doing this it makes it easier to locate the canisters, both types of canisters make a very distinctive sound, similiar to crackdown. The only one that can be a pain is the fury canisters, at a distance they can sound like the rooftop AC units. For most of the canisters if your in the general area of it you can hear them from about 100ft away, their sound will intensify the closer you get to them. Hope this helps.