Clients sometimes ask if they can install sound masking in a particular area within their facility. Usually, it’s due to a concern about an acoustical issue that’s more obvious – for example, an occupant who has a naturally loud voice or a meeting room in which confidential conversations take place.
I’ve commented on this issue before (see “Out, Damned Spot!” January, 2014), but it bears repeating because I continue to run across situations where vendors have advised their clients to spot treat and, surprisingly, there’s even a couple of sound masking manufacturers promoting products for this purpose.
Can you spot treat? Sure. Technically speaking, you can limit a sound masking installation to particular areas within your facility. But should you?
There are several well-understood design principles that our industry has known for decades. One is that the masking sound should be as unnoticeable as possible. Why? Because a successful implementation involves achieving masking effectiveness and occupant comfort – in equal measure. If occupants’ attention is drawn to the sound, it might irritate them. Then, you might lower the volume to try to improve their comfort level...also reducing the masking’s effectiveness.
A less conspicuous masking sound can be set to more effective levels. And one of the best ways to make sound masking inconspicuous is to ensure that it’s consistent. This basic principle is violated straight out of the gate if the system is only installed in a particular area.
By way of example, let’s look at spot treating an area outside a conference room. The client’s desire is to mask the conversations occurring inside that room. Here are the issues they should consider:
- The people outside of that room will walk in and out of the masking sound, constantly drawing their attention to the fact that it’s there.
- If the loudspeakers are installed facing down at the occupants rather than up towards the ceiling deck, the masking sound – and any volume changes – will be even more noticeable because the sound is directional, like the beam from a flashlight. If the vendor plans to add a visual indicator to let those outside the room know when the masking is activated, they’ll draw even more attention to the system’s presence.
- The problem is also amplified if the vendor intends to provide a control that allows occupants to turn the masking on or up when they ‘need’ it. This immediate change in volume will undoubtedly disrupt occupants in the treated area outside the room. You can mitigate this problem by having the volume change occur incrementally over a longer period...but only if you’re willing to wait a half hour or so for the process to finish before you start your meeting.
- If the conference room isn’t entirely surrounded by open space, what’s the vendor’s plan for neighboring rooms? If spot treatment only includes the open plan area outside of the conference room and not the rooms adjacent to it, then occupants inside those rooms will hear the conversation. (While you might think that ‘well built’ walls are enough to ensure speech privacy between closed rooms, guess again...or simply read my article, “Mind the Gap: Using Sound Masking in Closed Spaces” in Construction Canada.) So, will the control raise the sound masking level in the adjacent rooms too? What a surprise if the occupants are in the middle of their own meeting or a video conference call! It gets even messier if the vendor plans to equip each room with its own spot treatment and control, allowing occupants to variously turn their system on/off or up/down throughout the day.
Some of you know that we offer a programmable keypad with our sound masking system and may wonder at the apparent contradiction to what I’ve just said. Though it can be programmed to control the sound masking volume anywhere within the installation, the keypad’s primary role is to allow room occupants to adjust the masking sound within the room itself...not outside of it. For example, if you’re about to begin a videoconference, you might want to lower the masking to 42 dBA or less so that it won’t interfere with microphone reception. If you’re in the hospital, you might want to raise the volume so that you can sleep. The system’s administrator can program the keypad so that you can’t lower the volume to an ineffective level or raise it too high.
In the end, a sound masking system’s role is to control the acoustic conditions throughout your facility in the same way that you control temperature and lighting. You don’t want cold or dark areas and, similarly, you should strive to achieve a consistent acoustic environment...not have a low ambient volume in one area and an effective one in others. If low ambient levels are causing problems with speech privacy and noise control in one area, odds are that other areas are similarly affected.
I fully understand a client asking about spot treatment. Sometimes they believe they only have a ‘problem’ in one area. Sometimes they’re limited by budget. But, it’s important for the client to clearly understand what they are – and are not – getting from their sound masking system if it’s restricted to particular areas within their facility.
And it’s the vendor’s responsibility to communicate those drawbacks.