80 cfm duct booster fan, How loud?

One of the 4" from home depot will fit well into my small grow box, but I'm concerned it might be loud. Anyone know?

i have the 6 inch, 250 cfm model myself. a couple of things about these units; first off, the cfm numbers they give are a little misleading. while the 6 inch claims 250 cfm, that is only the max boosted cfm the fan can handle. otherwise, it will only move about 125 cfm on it's own.

another thing, they aren't that quiet. sometimes they have a tendency to whine if the conditions are just right, i.e. incorrect or restricted air flow. depending on your application, these may be ideal. you will just need to play around with the setup once you get the fan installed.

I may just stick with the 80cfm PC fan. I'm in a Rubbermaid tote setup, so 80cfm, with CFL lighting, will be enough to evacuate the room every couple minutes. Even running it through a carbon scrubber.