Camry :: Engine Making Noise Seems Like Belt Pulley Bearing Is Going Out

I have a 2009 Camry 5spd with 92K miles on it. Camry is completely stock and original with meticulous services to engine oil and drained the transmission fluid at 68K miles. I am hearing an engine hum every now and then (although I notice it more often now that I am searching for it) while I am idling. I don't believe it to be engine vibration, rather it is a hum, seems like a belt pulley bearing is going out, or even, and i hope its not, like my throw out bearing in the clutch is going bad.

Only reason I say that is because it makes the hum for a few seconds then goes away, then comes back for a bit. It makes the hum when i have the clutch engaged and when i have the clutch disengaged and a in neutral. I have opened the hood to try and search from where it is coming from but it is just too darn hard to figure out.

I am hoping it is nothing related to my transmission. I may pull the fill plug on it this weekend and try to stick my finger inside to see if I am low on fluids and it is making a hum (but I highly doubt it because when I filled it up after drain i filled it too the top). I haven't experienced any burning of oil and use 5W-20 (Castrol GTX since day 1). I may switch fluids on my next change and use maybe a different brand and viscosity (maybe use standard Quaker state at 5W-30).

Again it isn't an engine vibration, rather just a hum or almost like a stinking wobble and then goes away for a few seconds. I say wobble kind of like you would hear a drive shaft on a truck that wasn't balance properly and was spinning without being centred with counter weights.