Light banging / tapping noise coming from intake manifold area on 2003 Camry.

I have a 2003 Camry 4 cyl. around 60,000 miles on odometer and for around 3 months the engine seems to have gotten louder while at idle. At the back of the engine around the plastic intake manifold area the engine is making a light banging / tapping noise. It never made this noise before. The engine idles fine and the drives normally. I always keep an eye on the fluid levels and they are up to par. I'm not sure what is going on and if I should just keep an eye on it. I have provided a link below to a video of the noise. The noise can be heard best starting around 15 seconds into the video and fades away around 26 seconds into the video. What do you think could be going on here. Thanks in advance for any help. joet/camry

http://s126.photobucket.com/user/JOET1966/media/VIDEO0005-0_zpsaa1af77e.mp4.html

Check your compression. It is possible you have a bad head gasket/head bolts.

Take off the head cover and see if there is any strange appearance on the cam or any difference in clearance between the exhaust valve lifters and the cam when cold. This may point to a different problem.