Construct your booth at a height of seven to eight feet, six feet wide and six feet deep. If you're not building a freestanding booth, consider using either a closet or a corner of the room, using the existing walls. Either way, all walls, floor and ceiling should be covered in a soundproofing material such as isoTrax. Construct secondary walls, floor and ceiling over this foam before using another layer of foam such as that made by Auralex. Floors can be covered in low-lying carpeting.
Consider proper ventilation when designing your vocal booth. Recording engineer Kevin Lacy of Freudian Slip Recording states, "While it may seem to defeat the purpose of sound isolation to have a hole with a ventilation fan in your vocal booth, air quality is an important consideration." Once the door to a booth is closed and a session is under way, the booth can quickly become hot and the air quality stale, which is uncomfortable and ultimately unsafe. A ventilation fan should be a key component of your booth. Though no fan is noiseless, there are some extremely quiet ones that are worth considering.
Incorporate a window into the design only if absolutely necessary. "Having no windows in the booth will mean better isolation." continues Lacy. Consider running VGA (Video Graphics Array) cable, along with audio send and returns, so the performer can see a split feed from your DAW (digital audio workstation), or the text of an electronic document or script. Additionally, when choosing a door, a pre-hung exterior door generally comes with decent-quality weather stripping. Neoprene stripping can aid in further insulation.