What are some problems with harmon kardon avrs and speaker noise

Harmon Kardon make excellent AV receivers. If you hear noise from your speakers, look at your speakers first. Maybe they've been played too loud too often and the cone have come slightly detached from the magnet.

Check if your speaker wires are running parallel with power cords. They should be as far apart as possible, or if necessary crossing at 90 degree angles.

Try plugging the av receiver into its own outlet.