Atwood water heater won't light. High pitch sound.

Light on control panel is a 'fault light'.....should only light when:
Propane fails to light or ECO (High temp t-stat operates/OPENS)

Sound......?????

Never hear of one making a high pitch sound

Is WH tank full of water?
Have you turned it on propane and have it light off?
Have you left it on electric with tank empty?

Have heard electric elements crackle when covered with calcium/deposits

High pitch sound is strange.
Can you pin point noise to inside rv/backside of WH OR in outside compartment.