Need super quiet exhaust fan

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

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

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

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.

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.