After I experienced buzzing in my left ears for a week, I traced back what I did to my ears in the past several weeks. I felt that two things could be the cause: I started drinking more water than usual, and I started listening to certain music/lecture via ear-plug half hour before retiring to bed. First, I decided to stop the later to see if I could eliminate it out of the possible causes. Within 3 days of not using the ear-plug to listen to the music, I realized a huge reduction in the buzzing in my ears, and a week later, it was completely gone. It's been over a month now, I still have not experienced any buzzing in my ears ago. Whether it was the primary cause or just a coincidence, I can't not say.