while the microphone doesn't pick it up as well as i'd hoped, the noise starts at 3 seconds and ends at 13 in the above video. after several years of no noise i've noticed a weird clatter/rattle noise that only happens between 700-900rpm when the engine is warm. for instance i hear it quite clearly when the car is in drive and i'm waiting at a light or rolling into a parking lot. as you can see in the video, it does not make any weird noise at idle, it doesn't make the noise at higher rpm.. i'm a bit stumped. rockers all appear fine, set them when I installed them a few years ago and haven't had to do anything to them since. if anyone has any ideas on what that could be or what I should do to diagnose it further, i'd appreciate it.

to clarify, this video was taken with the car warmed up and i had the valve cover off because i was worried one of the rocker bolts may have loosened up or something. all are set properly, though i'm tempted to go through them all again.