Welcome to the forum. Although you can post in any forum, the USA forum is here in case of local regs or laws
You might find that a purpose-designed anti-vibration pad helps but don't expect miracles because the 5dBA reduction claimed by the Stuart Turner example I have in mind is noticeable but not dramatic. Stuart Turner have a useful checklist of things to consider/try:sitting on a plywood sheet - sponge strips attached to base
Reply to the thread, titled "house pump issue - noisy" which is posted in Bathroom Advice on Electricians Forums.
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