My old printer was a rattling box…
But without any engineering degrees or such to rely on I reverted to using logic and common sense to address the issue.
The machine came with the standard round pads, not too hard, not too soft.
Just good enough to prevent slipping.
When I was younger I had a passion for music and good DIY speakers.
Living in a multi storey building meant those base speakers transmitted the sound not just into my living space.
The solution to the problem was the same I applied to my printer…
Mechanical movement, vibrations, are transferred through the mating surfaces.
The more surface area the easier the transmission, the better the flatness the louder the the noise will be.
Thing with physics from the viewpoint of someone blissfully unaware of the stuff is that you can do things those who know would just ignore…
I learned from other audio enthusiast of the old days that the feet of the audio equipment are as vital as the equipment itself.
Like why does this vintage vinyl play use such flimsy and long screws for the feet ?
Or why does this old tube radio need those long legs and these half moon shaped metal caps at the end ?
The answer might surprise you: PRESSURE.
Some countries prefer BAR but basically all tyres come with a number in PSI - Pressure Per Square Inch !
Goes like this:
If you try blow up one of those rubber bottles to keep you bed warm you have a high chance it backfires and pops you lungs.
But if you try to blow up a weather balloon you feel next to no resistance.
The huge surface area means it takes a lot to build up and meaningful pressure and since the weather balloon also expands freely you have a hard time building up pressure.
Like it or not: The little pressure those tablets for vitamin drinks and such provide would be enough to blow the walls out of a room if the room is fully sealed…
How does this translated now from speakers and audio equipment to our printers ?
Try this for a change:
Print a cone with a sharp point as the feet and also a matching plate for the resting surface, e.g. table, with concave top - like an hourglass.
Now do some basic math - only if you want!
How heavy if your printer you said?
What is the combined surface area of the tips of these feet you said ?
No problem for the first but the second would be a very tiny number.
Translated that to PSI and you are in for a shock LOL
It can be a few hundred PSI working on those tiny points…
Now: WHY would this matter ?
SOUNDWAVES really struggle to make it trough very thin things like those points.
A bit like a filter if you like as the wavelength is usually longer than the diameter of the mating surface.
And with this intense weight transferred through those tips these feet are more like bolted connections with a bolt so thin that it can’t exist.
Why did I highlight the sound part you wonder …
Well…
Our printers not only created vibrations but also a lot of movement through the abuse of these laws of physics…
You know… For every action there has to be an equal and opposite reaction…
If you use firearms you know all about it - recoil…
The moving head makes the entire box RE-ACT in kind.
It is only how unflexible the box is and how heavy it is that compensates for this unwanted jerking around.
Using those pointy feet will eliminate a lot of the noise transferred and also helps a lot to keep the bottom stable and in place.
But it WON’T prevent the flexing and moving of the entire machine’s framework.
On the other hand those pointy feet REDUCE the TRANSFER of these motion but quite a bit.
Meaning that only the movements with the lowest frequency and highest amplitude will e transferred.
IF you have a very HEAVY and UNFLEXIBLE base than those movements can’t really be transferred 
For other things I do this by adding a heavy top, like from a discarded marble bench top of board.
You will find that, for example, on a concrete floor using pointy feet the machine housing does not really move and flex much at all.
Well, that is if you ignore that the housing itself is not THAT solid…
A neat way to cheat is to use a good sized table in a corner of the room and to use angle brackets or such to fix it to the wall.
With the table unable to move in the XY direction you only have to worry about those feet