If you have an iPhone or an iPod Touch, you can download a free app from the Apple App Store called iSeismometer. It is a mini seismometer capable of detecting vibrations in three axes. It is surprisingly sensitive. I place it on the platter of my TT and it can detect my footsteps and the running dishwasher in the kitchen. It should be useful for fine turning vibration control tweaks. No more guess work. Did I mention it is free?
I downloaded all 3 seismometers available for i-phone and tested them on my turntables. None of them are sensitive enough to use for vibration damping tests. Maybe someone has better results than me ? I used all the frequencies settings available.