Almost everyone with tinnitus notices it more at night, and the reason is mostly perceptual rather than physical. During the day the world is full of ambient sound — traffic, conversation, the hum of the fridge, the fan in your laptop. All of that gives your auditory system other things to listen to, and the tinnitus sits in the background. At night that input drops away, the room becomes quiet, and by simple contrast the ringing leaps forward. The signal has not got louder; everything around it has got softer.
There is a second factor on top of that. As you wind down for sleep, your attention turns inward. Without a task in front of you, your brain naturally scans for problems, and tinnitus is the most obvious one in the room. So you get a double hit: less external sound to mask it, and more internal attention pointed straight at it.
The practical fix is to give your sleeping environment a low, steady, neutral sound — brown noise, rain, a fan — at a level below the tinnitus, not above it. The aim is partial masking, not silencing. That softens the night-time spike for most people within a few nights.