How does Superman control his super-hearing? How does he manage to live in a large city without it being a hindrance?
The DC Wiki states that "He has shown enough control to block out ambient sounds to focus on a specific source/frequency." Since he is able to focus on particular sounds, Superman can just focus on the sounds in his immediate area, and therefore only have to process nearby goings-on. Superman also has a very strong will and large intellect, and so would be much less overwhelmed by a large intake of information than normal humans.