Making freaky noises when sleeping.?

This is very scary. I was awakened by my mom like 20 minutes ago. In her room across the hall, she was loudly making a noise like wiohwiohwiohwiohwiohwioh continuously, coming from her mouth. I screamed at her to wake up, and was freaking out because That noise was scary as he'll and loud. I know I wasn't imagining it because my brother heard it too. Could this be normal? It never ever happened before. If anyone has any idea what that could have been please let me know. Thank you.