I guess I should say that my transfer switch hums louder when I am on 30 amp shore power. When on 50 amp power it is much quieter.
My set up at home is a 30 amp plug and I use a 30 foot extension cord to reach the coach. The voltage at coach is only 118 with no load. That is well within limits and allows me to use lights, one A/C and the TVs of course. It also keeps batteries topped off and ready to go! I do hear the solenoid hum when it is quiet inside - very quiet. In RV parks, I never notice. Perhaps because of all the surrounding noises?
2015 Jayco Precept 35UN
Towing JEEP TJ with Roadmaster plates and bar w/Blue Ox Patriot brake
an Aluma low bed trailer with HD Road King and/or Polaris RZR onboard