You are right Ben, usually people who are mauled by Bears are mauled because they surprised the bears. That is why the bells etc. are good to carry when hiking. The bears hear you coming and move away before you come out of nowhere and surprise them.

There was a notice in a store I went to frequently in Alaska that was explaining bear safety for tourists.
It explained first, wear a bell because the bears will know you are coming and you won't surprise them.
Second, there is pepper spray that is designed for deterring bears and it is a good idea to carry this.
Third, if you see bear droppings it is a good idea to get out of the area. If you don't know how to recognize bear droppings they smell like pepper and have bells in them.

Kidding aside, yes making noise so that you don't stumble on and surprise a bear is the best thing to do, but it is not foolproof and sometimes bears do pull people out of their tents at night.
Carry the bell so that hopefully you don't ever run into one... but also be prepared to fight for your life if you have to. It seems that not a summer goes by that nobody gets mauled in Alaska. In Alaska I would carry a firearm... that is a much better way to protect yourself from a bear than a knife... but here in Hokkaido (yes there are bears here) guns are not allowed (it is possible to obtain a rifle and a hunting liscence, but it is not easy), so the best I can do is a big knife. If I am going to be camping in a kilt and carrying a big knife, it might as well be a dirk.