The sound you notice at the wheel may be different from what someone hears in the next room. A shifter click carries through the air. A low buzz might travel through a rig leg and the floor. Ask someone to listen from where the sound is bothersome while you repeat a short run.
Try the controls one at a time
Start with the rig off. Press each pedal, move the shifter, and check whether the frame or accessories knock as you get into the seat. Take a loose remote or bottle off its shelf and repeat the action that made the noise. Check cables that can tap the frame, leaving slack wherever parts move. Reusable ties or cable clips can keep those runs clear.
Then test powered equipment separately. Run the same short section with any bass shakers disabled, then with them on at your normal setting. Compare the sound in the other room. If the vibration follows one effect, try reducing that effect in software and listen again before changing the feet or flooring.
Keep the cockpit steady
If you try isolation feet or a mat, choose a setup rated for the load and check that each support sits flat. Retest with your regular braking force and check the rig and monitor stand for movement. Write down the one change that made a difference. A quiet cable and a correctly tightened bracket can be worth keeping even if you end up adjusting the sound or vibration settings too.