Vibration from garage door opener?

I was in a high end home yesterday doing some work in one of the children's bedroom when I felt, and heard this strange noise. Note the bedroom is directly above the two car garage. I was on my hands and knees assembling a bed I had just repaired, when all of a sudden the floor rumbled, and a grumbling noise got my attention. I said to the home owner "WHAT'S THAT", she said the garage door opener. I will be back in the home next week, and wonder if there is a way to INSULATE the unit so as to prevent the vibration transfer? I haven't looked at the mounting brackets yet, but wanted to ask for help B4 I return. Thank You, Dale in Indy