It's quiet but very noticeable when the radio is tuned to normal listening volumes. Actually, you can turn the volume completely down and the ticking sound keeps at a constant level. Obviously, when the volume is turned up, you can't hear the ticking as much. I'll have to check to see if it occurs when I play other sources.
I'm wondering if it has to do with the Active Noise Cancellation (ANC) system but I don't know. I put the radio into diagnostic mode to try to turn the ANC off and on, but I didn't notice a difference.
To put the Odyssey OEM radio into diagnostic mode:
Press and hold the "1" and "6" buttons at the same time and then press the "Power" knob.
I'm 30% to an oil change so this will have to be checked out by the dealership.