I have exactly the same. Every 4-5 days I get a high pitched circular saw spinning at ~14 kHz inside my head. I can mask it with pink noise (the Android app is called "Relief" from ReSound and is free). Funny thing is, when I mask it for 4-5 hours and remove the headphones, it is COMPLETELY GONE for like 1 hour. But then it ALWAYS comes back with FULL FORCE, hitting harder than a truck.
I am absolutely sure that you cannot habituate to that sound. I have had it for 13 months now, yeah I know it's not that long but it's also quite some time. Everytime I get one of "those" days, I tell myself "okay you can do this, it's just a sound, just don't listen to it" but I fail everytime. I can "ignore" it for like 2 hours but it is so goddamn intrusive, it's basically a saw cutting through your brain and after 2 hours, it's cracked through the hull.
Those days are very dark and I usually can only endure it with masking.
I can recommend the Samsung Galaxy Buds +, they have a very good battery lifetime of 10-12 hours, which is quite long.