How noisy are these 400 watt HPS systems

Are they silent? or what because i've never been around the things

mine makes no noise at all maybe a little humming when it first comes on then stops. good luck

A magnetic 400 water sound like a street light when running just that low hum but if its not secured it can vibrate. Those are the old technologies though. If you go digital they are silent no sound at all and the digital ones weigh about 4 lbs compared to 25 lbs for the old kind and they digitals are cheaper now.

I have a 600W digital HPS and it is almost completely silent. I'm a light sleeper and I can sleep with it on and the door open.