It isn't very loud at all, it's more of a slight buzz sound coming from the OZONE generator when turned to max, I have two of them, although 1 is sufficient, once again turned to max, to cover my 10 plants, 2 are flowering and they are auto-ak48's, I have 3 photo skunk #1, and 5 auto white russians, growing and this thing is neutralizing all of them in a room that is 10x11x8. I might have to use the second one, once I start my hydro grow of super silver, and 5 smurfberries. This thing also kills all airborne pathogens and bacteria. How much is it worth to you for that piece of mind?