a possible culprit just use a thin long metal or wood stick like a dowl rod and probe the accessories while creating the noise. I have a cheap stethascope from harbor freight for just such searching saves alot of time over R&R of parts. I think you have a noisy bearing.
Did this occur before the timing belt change? If not the timing belt might be missaligned with the crank sprocked or the tensioner or ideler pulley bearings are noisy.