Need super quiet exhaust fan

I have 2 remote fans for my equipment closet. 1 for makeup air & 1 for exhaust air. If you want to move air correctly you must use both or have openings to get or remove the air. If you use only one and you have openings it is best to exhaust the air from the top for circulation.

By no damper I was referring to the damper behind the grille. If present it should be fully open, not used to adjust the airflow quantity, and if possible it should be removed altogether. Correct, most domestic fans have backdraft dampers built in at the discharge.

Essentialaudio's details/tips are all good ones. You shouldn't need balancing dampers** unless you are exhausting more than one area, or have more than one return grill; in which case balance is achieved by adjusting the size(s) of the different intake registers relative to one another.

** Most externally mounted fan units are supplied with backflow dampers which close when the fan is off (to prevent cold air from entering ;-)

If you don't want to hear it, the fan *must* be remote from the room, with generously sized lined ductwork between the room and the fan, with at least one elbow. Use an aluminum or cast grille, not a cheap stamped steel one, at the room, and no damper (dampers generate noise). For 150 CFM I'd use at least a 12x8 duct...the lower the air velocity the less the noise.

For makeup air the transfer grilles, optionally with a filter between, are a reasonable choice. If the space from which the makeup air is coming is noisy, you will want lined ductwork with one or two elbows in it between the transfer grilles. A door undercut would have to be too large to transfer 150 CFM.

Again, Nsgarch is correct.
Don't use a metal duct hose to avoid more vibration.
Try www.build.com to find silent fans

Thanks guys. I like Nsgarch solution.

Nsgarch's solution is clearly a better mousetrap. Outside of that, Wpines is right. Panasonic is the way to go. For a ceiling mounted fan, they are spooky quiet.

The quietest solution is to put the fan on the roof (one storey) or on an exterior side wall (if there are floors above you) and connect a duct to the equipment room ceiling.

Regardless how you decide to do it, you also need to think about where the makeup air is coming from. If it's coming under the equipment room door (undercut) it could have a lot of dust in it. Better to install a "transfer grill" and filter, in the door or interior partition wall of the equipment room.

Rather than going to a big box retailer and getting the best they have, check with your local plumbing supply shop. As a contractor that's were I go to get the super quiet models. Of course a remote motor is the ideal solution, as has already been mentioned.

If you must use surface/ceiling mount, look into Panasonic.

Inline type would be quieter than most. 150 cfm would be about 6" ducting.

I used the quietest bathroom exhaust fan I could find for a dedicated equiptment room which has a seperate door between it and my listening room and you can hear it when the door is open so I dont suggest that for a room you are sitting in.
In my second listening room the equiptment is in the room with me and I found that Active Thermal Management makes the absolute quietest fans for listening rooms. I had one installed and it is virtually impossible to hear when it is on. You can only tell if it is on by checking the switch. All of their products are highly recommended.
http://www.activethermal.com/
Rick