I have the same. The interference should mean that there's less acoustic energy, but since the anti-sound wave won't always be a perfect match with the wave being cancelled I suspect the result is that there will be soft beats[0] of very high and/or low frequency that may still stimulate the ear in a way to trigger tinnitus. The first time I put on my noise-cancelling headphones it made me dizzy - that is also likely caused by low-frequency beats.

Anyway, I just lowered the volume, that seemed to help quite a bit. I don't need the higher volume anyway now that the surrounding noises are cancelled.

[0] https://en.wikipedia.org/wiki/Beat_(acoustics)