What sound have you ever seen how fast they opened?
http://www.youtube.com/watch?v=lsjmO5YdNOc&feature=related
Cool video. They sure are fast but that doesn't mean they are silent. They are mechanically or hydraulically operated and stuff like that typically makes some noise.
you can hear and feel flaps and gear deploying in a commercial airliner, why not bomb doors in a bomber? 
Yep. Hell, we even can hear the wing slats pop in and out with the engine running.
-1 Unrealistic.
Is this based on your in-flight experience with the B-29 you have at home? We also have the nondescript "base under attack" sound, which doesn't seem too real. I turn that one to zero, as you could do with the bomb bay door sound.