I've faced this problem before. When I had a 100x objective on OpenFlexture and I was looking for fine details of ICs, there was some vibration. I've tried to turn off appliances but it didn't help enough. It looked like the electricity making this interference. I didn't know what is it and how to remove this interference. 

Now I know that it was simple acoustic noise and the easiest way to reduce it is using iner tube and brick. (In my case box with rocks) 

Nothing fancy box with rocks and iner tube. 

At first I put a two glasses of water one on the box and one on the table. Vibration was more powerful on the box one. 

It was counterintuitive for me, it took me some time to realize that waves inside a glass are low frequency what I want to see is how ot will behave under the microscope.

Without vibration reduction 

You can see how it gets really blurry once I knock on the table. On the other side with vibration reduction, I got

You can see that this simple but effective mechanism is working.