If the noise came from the sink, it means your gray tank has filled to the point where the drain from your kitchen is submerged in water in the gray tank.
This has nothing to do with a problem with an air admittance valve, but if you removed the air admittance valve from beneath your kitchen sink (or wherever else it may be for that part of your gray water system), the problem would stop, but that’s not a solution because doing this will allow the smells from your gray tank to escape into your RV. The only solutions are to empty your Gray tank, which is only a temporary solution, or have the drain from your kitchen raised to a higher point within the gray tank, which is the real solution.
2016 Rockwood Windjammer 3029W Diamond
2015 Chevy 3500HD LTZ 6.0 Crew Cab 4x4 Long Bed 4.10:1 SRW