This would actually be classified as impact noise.
Are these rooms, bottom floor on concrete slab? and what type of flooring do you have? Wood floors or carpet?
Also is there a door for the room that has the treadmill and is it closed when the treadmill is in use?
And is your bedroom door closed as well?
Also are the doors hollow core or solid core doors? most common interior doors are hollow core.
Here are a few link to review while we help determine what solution will yield the best reduction.
This link will address the treadmill.
http://www.soundproofing.org/infopages/vibrationpads.htm#VibThis link will address the doors.
http://www.soundproofing.org/infopages/soundproofing_doors.htmwhen you answer the questions above I will be able to give you a recommendation.
Thank you.