I don't think most most people can control their sneezes. I know I can't, but mine aren't that loud. They aren't exactly little delicate things, but they're normal volume, I guess?
I have a colleague whose desk is near mine, and he sneezes so loudly that, yes, I always jump involuntarily. But I don't think he can do anything about it, so I just deal. That would be my advice for the OP too.