A few possibilities:
>Water pump is cycling due to a small leak
>Electric fuel pump is pumping to maintain pressure in the system even though it should be off when the ignition switch is in the off position.
>Air bubbles in the water system or hydraulic leveler system
>From the suspension or leveling system when the coach jiggles from some small movement like when someone walks or re-positions in a chair
>My Lazyboy recliner developed a electronic sounding squeak when fully reclined and I would breathe