Product review (5 stars): New solenoid is quiet and works!
Just purchased a home with two humidifiers.  Solenoids are 10 years old and evidently previous owners performed on maintenance.  One old one was completely inoperative and I replaced it, the other partially blocked but should hold up for another season. Both old solenoids buzzed at ac line rate so I am not enthusiastic about the durability of the "oem" parts, but they are easy enough to replace with this solenoid and came with reasonable directions.  The new solenoid works and is quiet.