For one you're implying that life other then us exists, which is probably true but not empirical because it has not been proven. 2nd you implied that said life has to be intelligent and using standard earth radio/radar system, odds are if they do have technology it's probably developed from an entirely different path then ours. 3rd you implied that the possibly intelligent life has to be looking for us, what if they're religious manics or a race of warlords or a puddle of sentient bacteria. Please don't make assumptions about life other then our own. Also owing to the immense size of the universe and the far larger size of any multiverse that could exist, it most likely means that radiowaves interference is impossible. You really need to think about the true vastness of space though.