As people get older, sometimes they forget what it was like to be young. Also, they can be more easily irritated, and less inhibited about saying what's on their minds. Just be patient and understand that it probably has less to do with the way they truly feel about you than it has to do with these factors.
We're old! Old people have various health problems, some of which cause a lot of pain! Plus, we've earned the right to be grumpy!! I doubt they're yelling at you for "nothing"! Maybe, you're loud or annoying, I don't know but I bet there's a reason!