Yeah I feel like the total silence causes me to focus on the ringing, which raises the intensity -- I think it's a mental thing.
Whenever I use noise cancelling headphones (or really any headphones), I always have something playing even at a really low volume to drown out the tinnitus.
I'm a bit odd in that I prefer total silence, though my wife needs background or white noise.
I'd rather just have the ringing in my ears than ringing PLUS something else. There's something distinctly different between ANC and true silence, and despite several attempts I've never found an ANC that proved otherwise.