Noise cancelling devices for large rooms

Another solution, yet substantially more expensive is to install double or triple-layered glass windows with air or vaccum between the glass layers and plastic + wood framing (avoid aluminum, since metal framing is an excellent noise transmitter. These kind of windows are usually expensive and require a substantial amount of money, specially for large rooms with large windows. I live right next to a farm server company that operates 24x7 with over 40 air-conditioning ventilators installed on their plant roof, thus sending severe, constant noise pollution to the environment. My sleeping room is large with large windows and faces directly those 40 ventilators. Since I don't have such a large amount of money, I will try your inexpensive solution and see if that is enough for my room. Still if anybody is aware of a better, more practical solution, please help Owyn and me, please!