That guy who makes marble music recently worked out a ball funnel that uses inserts in a different material to eat most of the noise. But in that case it’s also eating momentum as well so I’m not sure how that would work for this design. Maybe some bushings in the supports to reduce harmonics.
Now my brain is doing it's usual "over complicate things to the extent a project cannot possibly get started" thing"...
Active noise cancelling. Vibration detectors on oscillating parts of the track with LRAs or similar actively driving opposing vibrations. Might be able to use whatever the cheap active noise cancelling electronics headphones have? Might be able to use a high speed camera and video motion amplification to work out the best places to deploy it?
How you mount things matters a lot, and adjusting shapes to prevent harmonics might be something this guy could add to his algorithm.
I saved a couple friends in college from getting into fights with their downstairs neighbors by finding them milk crates to set their speakers on so the bass doesn’t all end up in the floor. Isolating from the base or making the base of TPU could likely help.
