Hi Guys! I own a Cessna 205 with a 3 blade Hartzell Prop and a Continental I-O 550

The thing is, the propeller has started to make an almost unnoticeable Pulsating Sound during cruise flight.(you can only hear it with the headsets on)

No real vibration has been felt, just the sound, like when you are flying a twin and the props are not well synchronized.

If I set the RPM’s lower than 2,200 the pulsating sound slows down until it goes away.

What could it be? Does it sound dangerous?

My guess is it's a "harmonic" response from something loose on the airframe, have a good look around, loose inspection cover, missing cowl fastener etc.

How long since prop overhaul? Can the sound be heard from the ground when you are taking off?