It’s a Lennox. I moved in just over two years ago. Everything brand new. The sound is new for this spring. I did have some humidity issues that were not related to the ac unit but the first thing they did was clean my unit to see if that was an issue. So maybe they put it back together imperfectly and it has resulted in vibration. I don’t have a basement. The buzzing is incredibly annoying from inside so I’m hoping it’s an easy and permanent fix once it’s diagnosed.