They build mufflers. But I have a 465 cfm fan and it is super quite.
Depends on the brand.
The hoods I'm using now are are cooled. They belong to Zandor. Thx Z!
I hooked up my fan to one light. And it stays so cool under this light. It blows my mind. 76 right under the light! The plants are loving it. Growing the fastest I've ever had MJ grow!
Cool Tubes it is then...I think if your using more then one light. Cool tubes are way more efficient.