Anecdata, but another case here. I wear them approx. 6 months per year because of knocking heating sounds. Anyway, doctor recommended to do ear cleansing once a year and it helped, maybe 80% of the ringing sound is gone. Earplugs caused all the grease to end up compressed and deep in the ear canal. After a while it blocked signal transmission through the auditory nerve enough so that my brain thinks there's no audio input and it starts compensating with these imaginary ringing sounds.