What device?
I've never had that problem. My theory is it depends on the actual notification tone. Did you change yours?
Nope, did not change anything. I just know a lot of people complain about low notification sounds on the Moto Z line. They've never been low enough for me to really care, but they suddenly seem higher, and plenty loud I'd think for anyone.
Without an update that's odd it would suddenly be different
Mine are still quiet unless I do the workaround "fix" using Device Help and speaker test. I was hoping the next update would fix but sounds like even the 7.0 upgrade did nothing.