In this month’s Facility Management Journal (pages 78-82), I talk about how to prepare or evaluate a sound masking system specification. I’d like to take this opportunity to stress the importance of keeping adjustment zones small, because it’s so critical to the successful implementation of this technology.
To quickly recap: adjustment zones are groups of loudspeakers for which you can establish individual volume and frequency settings. One loudspeaker in each zone is ideal, but it’s acceptable (and perhaps more budget-friendly) to have up to three, at least across open plans. In fact, most systems use a mix of small zone sizes throughout an installation.
Small zones ensure that the same loudspeaker settings don’t cover dissimilar spaces. While avoiding having a single adjustment zone cross both open and closed areas is obvious, it’s also necessary to avoid a zone that covers different types of closed spaces or even large open plan areas. Why? Because occupant requirements and ambient conditions vary, even across open plans. In fact, I recently reviewed an independent acoustical study that showed the unmasked ambient level changing by 6 dB over short distances within an open plan. And, guess what? That’s not unusual.
So, you can’t ensure a consistent masking level by simply ‘blanketing’ the space with a sound using a single system-wide setting. Not only do the facility’s ambient levels vary, but the masking sound is also affected by its interaction with the workplace design and the materials used within it. These elements impact the sound regardless of where the loudspeakers are installed. In other words, 48 dBA may be what you want to achieve, but you won’t get it ‘out of the box.’ You have to be able to address local issues where they arise.
If the zones are large, you can’t increase or decrease the masking levels only where needed. Instead, large areas are affected. So, while you might resolve a problem in one area, you’ll very likely intensify it in another or create a new issue altogether. Also, the larger the zone, the greater number of people impacted by these variations in performance.
Small zones offering fine volume and frequency control allow you to address local variations and achieve a consistent – and, therefore, consistently comfortable and effective – masking sound. Note that “fine control” doesn’t mean a 3 dBA transformer tap on each loudspeaker; these are too crude.
In the end, large zones simply don’t perform. While they might reduce the initial purchase price of your sound masking system, they’ll carry a steep cost in terms of comfort, effectiveness and flexibility over the life of the system.
That’s why zone size is the first thing you should discuss with your sound masking vendor and should also form the basis of any sound masking system specification.