Feedback from opening CD door; HELP

Especially if it is faint, I would say that there is nothing to worry about. The speakers are simply responding to the signal they are receiving just like they do when they reproduce your favorite song. If it was a longer signal with a DC component, it could cause damage to voice coils. This would be noticed as the cones of your speakers moving outward or inward and staying there for a noticeable amount of time.

Move player away from amp/reciever especially if it is sitting on top. I had the same problem with a Denon and once I moved it away from the amp the pop went away.