The treatment of a vocal booth is very simple. First you need to ascertain how ‘dry’ you need your vocals to be. If you are recording vocals for radio or commercials etc. then your vocal recordings need to be quite tight. If the vocals are to be used in songs then you need some reflections from the room to keep a live sound to the recordings.
Most vocal booths need between 50% and 75% coverage of the surface area including the ceiling. The drier you need the vocal recordings the more acoustic treatment you need to install. Almost never would 100% coverage of acoustic foam be required in a vocal booth as this total coverage will take all the life out of the room and the recordings. The person in the booth will feel like he or she is under water and these excessively dry rooms can be more of a hindrance than help as extra mastering work is required to add reverb to give the recordings a little life.
When treating a vocal booth you need to use acoustic tiles that can effectively absorb the whole of the frequency range of the voice but also do this evenly to give you accurate results in your recordings.
The acoustic tiles there were specifically designed for use in a vocal booth is the F.A.T. PRO Acoustic tiles or the Wedge PRO Acoustic tiles because they are very effective down to the lower frequency range of a regular human voice. Other products that could be suitable are the Euphonic Standard Acoustic tiles.
If thinner tiles are used then mainly the higher frequencies are absorbed which results in uneven and inaccurate recordings which will come out when put together with music and when editing the vocals together. Thicker acoustic tiles are not necessary as they would be overkill and would be too effective making the room too ‘dead’.
The acoustic tiles mentioned above are the best solution when it comes to treating a vocal booth. In terms of placement of the acoustic tiles, the coverage needs to be as even as possible but focusing the coverage from the waist upwards. Also don’t forget to allow acoustic treatment for the ceiling as reflections from the ceiling can be damaging for recordings.