Best sound insulator?

[DaOld Man]

I am working on a photobooth with video and audio messaging options. (Project announcement coming soon, still in planning stages.)
The photobooth is actually a box that can set on a table, or inside a booth.
The box will be made out of white pine board.
I will need a fan to exhaust any heat.

My plan is to put a microphone and speakers on the front, under the monitor.
The speakers are so users can preview their video and voice messages after creating them.
My question is, how do I insulate the sound of the fan and possible speaker hum from the microphone?
Shouldnt have to worry about feedback since mic and speakers should not be working at same time, however speakers may lightly hum when not outputting sound.
I can use a relay to disconnect speakers when mic is recording, if necessary, but I will still need to insulate the fan noise.