Toilet making high pitch eerie noises?

[Tempest]

I quickly googled my question but couldn't find an exact answer so I'm asking the community!

For some reason today, my toilet decides to make high pitch eerie noises. It's really loud and I had to close the door to the restroom AND the door to the room to block some of the sounds off.

When I flush the toilet, the noise stops. After a few minutes, I'm assuming when the water fills up again, the noise begins again.

What could be wrong?
A quick note: The sound hasn't stopped for several hours until I flush it. Thanks for the tips and I'll check it out. Will update if anything new arises.

[vicecaptain]

Maybe some rat would have got into it....