Just recently I have been hearing this strange rubbing or knocking sound from the front of the car. It's very low and I only hear it when the car has warmed up after a few miles of driving and only when going over bumps under 20MPH. If I have the music on I can't hear it. Suspension feels normal. Sometimes I hear it only from the passenger side and sometimes only from the driver side. I did notice the spring pad is sort of rubbing on the spring. Picture attached.

Any ideas?