Hi,
I set up a vocal booth a while ago, which doubles as a mini DIY studio
The computer is outside to reduce noise - I use Windows. I connected a second monitor to the pc plus second mouse and keyboard.
There is a music interface inside the studio for instruments and one outside for microphone. I had problems on bringing microphone and interface too close together. I built three letterbox type of cable vents into the bottom of the studio walls, so I have all the wires and plugs I need.
I can operate my mixing software [MixCraft] from inside the studio, and monitor on speakers or phones. There is also an analogue mixing console in the studio which I use as a preamp for microphones and electro-acoustic guitar.
The walls are paneled with hardboard and the spaces filled with insulating material (wool) so that cuts about 2/3 of the loudest sounds - enough to keep the neighbours smiling. The door is fitted with thick polystyrene panels on the inside.
Air enters the space through a large plastic duct pipe affixed to a nearby vent window to the outside world. Another pipe exits the studio where an extractor fan sucks air out of a window 10-15 feet away, far enough to lose all sound from the fan and after carefully positioning polystyrene sound baffles inside the hose pipe.
It took weeks of trial and error to iron out all these glitches after the unit had been prepared, but it's a great space to sing and record now, or use the electronic percussion or even the internet. But for serious 'sitting down to the computer' I switch to the main monitor outside the studio.
Hope this might help?
Ric