Sounds like pretty normal behavior for an RV water pump. I just live with it. Although I've researched the whole to get an accumulator or not. I did just replace my pump and lined the space it's in with foam board. It is quieter, but not silent.
2012 FunFinder X 210UDS
4-68 watt flexible panels; 1-215 glass panel/4 Battle Born LiFePO4 Deep Cycle Batteries
2014 Ford F350 6.7 Liter PowerStroke V-8 Diesel longbed, SRW