A subreddit for advice how to keep my upstairs roommate from hearing everything that goes on in my room?

I need to ask how to maybe soundproof or...something my ceiling because my upstairs roommate just told me that she could hear me like I was in her room when I was just on a phone call. I definitely don't need this same issue for when my girlfriend comes over or if I'm watching a late night movie.

Where do I go for advice?