At our dollar tree store they have the braided throw rugs for $1...you could fold them and put them under the machine. Have not used one...I use the nonskid shelf liner with mine...but if you needed more sound muffling...the braided rugs might work.
just a thought.

I use the cheap anti - slip mats and they work very well.

I just use a towel folded up under mine.

I actually have two of those Janome mats I got from our local dealership (free with machine purchase) - side by side under my embroidery machine. I have to admit that I really like it.
I never thought to take one with me for taking classes with bouncy white tables. I really hate those tables! If I get to take a class again, I'll try it out :)

I have one & a Janome 6600P. I got it because the extension table kept moving away from machine when I sewed. I tried the rubber shelf liner (didn't work all that well), so bought the pad. It doesn't work any better, but I do like having a giant pincushion right beside the machine that doesn't get knocked off!

I made a cute mat for my machine from a pattern I found on Joann website. My machine still walked so I put the non skid rubber shelf liner under the mat. Why didn't I think of that sooner ?? :/

I use a cutting matt that was left in the sun too long. You know what happened. I think in the back of my mind I was hoping the weight of my Bernia would flatten it out. Haha No such luck. But it is nice to have the numbers in front of me when I need a quick measurment - I don't have to get up to my other cutting mat or get out the tape measure.

I made mine from some prequilted fabric I had stuck in a drawer--works fine. I made it wide enough some hung down that I made into tool pockets. Cost=more drawer space and some stash reduced!

Same here. I think a sturdy table is more important.

If your machine vibrates and makes noise, it may be the table you're sewing on and not the machine. I find when I go to a class and the tables are less sturdy than the one I have at home, this will happen. Perhaps if a new table is not in the cards, try moving the machine closer to one of the legs. This is generally a sturdier spot, and may not cause as much vibration.