@stan2004 posted:A bridge rectifier in and of itself will not reduce the buzzing in a solenoid. That is, the voltage still rises and falls 120 times per second except the pulses are all in the same direction (positive or negative) rather than alternating positive and negative. You need to smooth the pulsating DC with a capacitor...or use a DC power source such as a DC-output wall-wart.
It may reduce it some, depending on the characteristics of the solenoid. Since the frequency is effectively doubled, sometimes that helps with the buzz. Also, the fact that the polarity isn't reversing may be a factor as well.
OTOH, I do agree that I've had issues with relays just using a bridge and adding the cap did the trick.
