About a decade and a half ago, I was riding a bike that I had recently built up. And I noticed a slight squeaking noise down in the pedal and crank area. I had a multi tool with me, immediately stopped and started checking everything down there. The drive side crank arm bolt was pretty loose, I tightened that up as tight as I could get it with that small wrench. And went home and used a torque wrench to tighten that bolt to specification.
This would not solve your noise problem, but I can say that when i tighten that bolt on my bikes with a torque wrench, the bolt stays tight enough that it stays in the bike and does not fall out. But the bolt will be noticeably looser after several hundred miles. I never worried about it being looser since the crank arm stayed in place and I installed it to manufacturer torque specification.
I suspect (this is only a guess) that the crank arm slowly tightens onto the square taper spindle over time because the bolt continues to apply pressure against it and that was enough to cause the bolt to become slightly looser with some distance on the bike.
Since then I usually use a torque wrench on crank arm bolts. The exception is that when I take my bike on an airplane I have to remove the crank to fit it into the case, for that I do not use a torque wrench as it is too big and heavy.
I have heard that if you ride a bike with a crank arm bolt too loose for too long, that can damage the crankarm. Fortunately the one time I did that, I did not ride it enough to cause damage.
