The interrelationships between various aspects of workplace design are interesting and it’s worth keeping a watchful eye on them as you select the materials for your space.
Speaking of eyes...take visibility, for example. Designing with this trait in mind can have some rather surprising impacts on acoustics.
Let's start with light fixtures. If you choose a traditional flat acrylic lens for your space, you’re replacing up to 20 percent of your absorptive ceiling tile with sheets of hard plastic, increasing the reflection of sound from the ceiling back into your workplace, raising overall volumes and reverberation (echo). This effect will be even more pronounced if any of the lenses are located directly between two workstations. In this case, a person’s speech will be reflected right down into the adjoining workspace.
If you have to use an in-ceiling fixture, opt for a deep, parabolic lens instead. At least the sound that’s reflected back into your space will be more dispersed. But the best approach is to use a suspended, indirect light fixture. Most are narrow, curved and perforated, so they maintain the absorptive surface of the ceiling. They’re not intentionally designed to for acoustics, but it’s a happy coincidence.
There’s yet another way in which designing for visibility impacts acoustic performance and it has to do with creating sight lines between people. If there’s a direct line of sight, obviously there aren’t any physical barriers between a talker and a listener, so sound transmission will be high. But something we do naturally makes this situation even worse: we read lips.
How much you understand of what someone’s saying depends on whether or not you’re looking at them. If you’re unable to see the person talking or you’re looking away, you understand less. So, in situations where there aren’t any physical or visual barriers, a person’s degree of privacy is largely determined by whether or not you’re watching them.
This effect is known as visual cues. It’s been quantified in various studies, but I’ve also seen it at work in my own family – my grandfather’s been lip-reading for years because he suffers from occupational hearing loss (he turned 101 this year, so he’s quite an expert). Quantitatively speaking, if you can understand 50 percent of someone’s conversation when you aren’t looking at them, watching them increases that amount to nearly 90 percent! If you start at 20 percent comprehension, visual cues increase that to around 55 percent.
So what does this mean for workplace design? It means that if you choose to lower workstation partitions below seated head height, it will have doubly negative consequences for privacy and distraction. Not only will the lack of physical separation allow speech to travel more easily and be more clearly understood, but the ability to see (and be seen) will further reduce privacy.
The conclusion? Sometimes, it’s better to be neither seen nor heard.