This is the second in a series of ongoing blog posts aimed at giving you a blow-by-blow account of our upcoming move to our new offices and the ensuing adventure of building out our new state-of-the-art usability labs.
When building a usability lab, you have to take into account some basic physical considerations such as:
- You need two adjacent rooms to represent the control room and user room.
- Sound proofing between the control and user rooms.
- Sound-proofing the usability lab from the outside and vice versa.
- A two-way mirror that allows observation of the user room without being seen.
As the floor plan included in the first part of this post showed, of the four usability labs with the paired control/user rooms, three share a wall with one or more labs and one shares a wall with an office. When sound-proofing the lab as a whole, one of the major structural changes to keep in mind is to ensure the walls go from the floor of one level all the way to the deck of the floor above. Normal office buildings have 2-3 feet between the ceiling of one floor level to the deck of the floor level above, usually with panel/grid ceiling tiles. By taking the wall all the way up, you keep the sound from reaching into empty spaces above.
There is extra cost involved in building these walls but the major cost incurred is to ensure that 1) the HVAC is designed to go through the walls, and 2) for special sound dampeners to be placed in the ducts between the rooms.
Lastly, where the labs share walls with other labs, we have to ensure the walls are constructed with extra sound insulation inside them. Two major sound-proofing options we have chosen to forgo until we test out the new labs are the sound dampening of ceiling tiles, and a installing a type of sheet rock called ‘quiet rock.’ Together, these two options could add $5,000 to the cost of each lab. The decision was made to wait on these options because they can be easily added after initial construction if it is deemed necessary at a later time.
What is the first thing that you think of when you think usability labs? For fans of Castle or The Mentalist, it might be watching Beckett or Cho (this character really needs his own show) conduct interrogations on the show from behind the two-way mirror.
The design of our current two-way mirrors has been very effective and we intend to utilize the same design.
For two-way mirrors to work effectively, you need to limit the sound that travels through the mirror between the lab and control room, and you need to limit the amount of light in the control room because with the wrong lighting, you can still see through a two-way mirror. Glass obviously is a great conductor of light but it happens to also be a good conductor of sound so the effectiveness of the mirror coating and dark flat paint in the control room help with most of the light issues but not the sound issues.
One of the most effective techniques to address the sound issue is the use of a unique double-paned window approach. This also helps diffuse the amount of light from the control room.
As you can see from the architectural diagram above, the two-way mirror is set flat in the window frame on the side of the user room and a second piece of plain glass installed on the control room side is set at an angle starting about ½ inch from mirror angling so that at the top it is 2 inches away from the mirror. (I’ll save you from a riveting physics lesson on why the angle of the glass disrupts the sound and light waves more than a normal double-pane window! Let’s just say it works.) The result of this is that voices are muffled so no normal conversation can be heard between the two rooms.
One structural requirement for our new usability labs not listed above is the need for dedicated HVAC in one of our labs. In most office buildings, air-conditioning and heating are only turned on during regular business hours. For our new office space, we have set up one of our labs with a dedicated HVAC system so we can run studies nights and weekends. Not all labs need this option, but with the increase in international remote-testing that we have been doing lately, and the vast time zone differences and having to work on weekends, and all night, when doing international testing, this is an option that would make sense for us. This of course adds additional costs and design considerations to the build-out.
We currently are in the process of getting bids on the audio-visual portion of the new usability labs and focus group room. The next blog post in this series will be about this process and the options we choose.