There was an article posted here a while ago that described how people from elite schools always talk with confidence even if they have no clue and how this is a recipe for success.

If you are soft spoken I think the only way to get peace is to get in a position where you can control your part and can ignore louder people. I have done this at previous companies and in the long run you get noticed by your results. If you can't find that place it's probably better to look for another job.