Alternative solution.
If you have as hard of a floor as it sounds like you do, place some large speakers facing down directly onto the floor. Play Yoko Ono songs 24/7 for a week at a high volume (it's highly suggested that you take a vacation during this time). When you return, you'll find that the noises from below have magically stopped (plus you'll have more space which can maybe be used as a studio?).
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