Weird noises from my rat

Question
QUESTION: My rat is very chatty and recently she has been making this weird noise.

This has been going on for a few months, she would sometimes whine. Its not loud, but in a quiet room, you can hear her. I first heard this when she was up in the hammock with her three buddies. She would sniff, then her ears would go back a bit and let out a quiet whine.

She got stuck behind my bed, i was reading and i heard her little whine, i helped her out, she stopped.

My eldest rat passed away and she got attatched to my brothers older rat, she whined when i put her friend at the bottom of the cage, her friend instantly started climbing and grunting to her.

Is this a distress call? is she stressed? sometimes she will do it randomly.

ANSWER: Does it sound like she is grinding her teeth together real fast?

---------- FOLLOW-UP ----------

QUESTION: no teeth grinding or chatting. I find it weird because its not like a rat to whine, it sounds just like a puppy wanting attention.

She shows all the other normal behaviour such as bruxing and eye boggling before going to sleep, the fast little grunts when she is having a blast on my bed and the little chatter as she plays tag with her buddies.

Answer
My rat used to whine when he would see the cats. It was a typical whine that would break your heart.  A whimper actually.  It did not sound like it was supposed to come from a rat, but more like that of a puppy or even a dog whining.  Is this what goes on?  If so, its not super normal, but some rats do whine or whimper when stressed about a certain situation.