You can’t hear a thing.
There are 4 settings on a remote for the stimulator.
3 you can actually feel the vibration in your back and legs. Depending on your issues the representative will program it to give you the best results. Over time it may need to be adjusted.
I actually like feeling the vibration and I use that setting during the day. For sleeping I use the one you can’t feel.
It’s been life changing after over 4 decades of chronic pain. Had to go through 3 surgeries, every type of injection, 3 years of ablations that provided minimal relief before I was offered the stimulator.