Are you sure you don't have BSFL in there? From what I have read, BSFL DO make noise.

That's just the sound of happy worms! Congratulations! I love when my bins sound like that.

my rubbermaid bin makes those exact noises.

Mine doesn't make noise, but the surface of the bedding undulates.

Mine will occasionally make noise, and I don't have any BSFL.

Mine makes them and I have not seen BSFL. When my bedding starts to get more decomposed I will start to hear it more.

How many worms and what kind of worms do you have in your bin that they can create noise like that, or make the bedding ripple? And how big is your bin?

EFs in a 14 gallon Rubbermaid tote. I don't know how many, but they are pretty thick in the bin. I don't always see the movement, but if I spray the surface of the bin, or sprinkle something over the surface, the surface definitely moves.

Hmmm, maybe I don't have enough worms, yet.

My noisy bin is a can-o-worms with all 3 trays, with about 5000+ worms in it

I've noticed the same from time to time. I think that as long as the worms aren't telling you to do something for them you should be fine.

LOL Rom. I think I heard the words, 'more watermelon!!'