Just a quick post, using NVH to check wheel bearings on the ramp. The laptop was running off the mains charger cable, I noticed peaks on the readings at 50, 100 and 200 Hz, puzzled me for a minute because the car was not being touched, then realised mains voltage supply in the UK is 50 Hz, put the laptop on battery peaks all disappear. Just something to be aware of.
I've experienced the same problem a couple of years back. In my example we found after investigations that the cause was the laptop mains supply was not filtered. I purchased a new main supply cable with a built in filtered and all was okay.