You can use frequency analysis to isolate the problem. The sound is a really low-frequency problem, sounds like about five thumps per second, or 5 Hz. Now, what part of your machine cycles at around 5 Hz? Your wheels move faster than that, about., 35 Hz, so you know that it is not a sound made by the wheel every time it spins around. Assuming a speed of around 3000 feet per minute for your band saw blade, which is typical, and a blade length of 96", that means your blade makes (3000*12)/(96*60)= 6.25 complete rotations per second, which is kinda close to my guess of 5 thumps per second. So I would first suspect it's an issue associated with the blade making a thump every time it makes one turn. Maybe the blades aren't tensioned well and the weld is hitting something as it goes around? (This is a very amateur attempt at frequency analysis but skilled industrial mechanics do this sort of thing all the time for very expensive machines... Put a mic on it, calculate the frequency of the troublesome noise, find which part in the machine spins at that frequency (or a harmonic of it), and bingo problem identified.)