To continue from last week: A sound masking system will always perform as it should, as long as its spectrum and volume are adjusted correctly to meet the desired masking curve.
But the overall performance of two spaces – even with identical masking implementations – may vary significantly due to the impact of other elements.
One of the main differences you may notice is the distance required for the masking system to achieve certain levels of effect. And that brings me to my final point. Masking does, in fact, require some distance to work. And you want this to be the case. After all, work is stressful enough without everyone shouting to be heard!
Distance is a factor because a noise’s volume drops as it travels away from its source. As I mentioned in Great Expectations, Part I, the volume of this ‘signal’ must be compared to the masking sound’s volume in order to determine how much masking effect occurs. For example, if the noise has travelled ten feet and its volume is still higher than that of the masking, the person may notice it. If the noise has travelled twenty feet and its volume is at or below that of the masking, the person won’t hear it.
So, what does this mean in general terms?
Well, the masking won’t have a noticeable impact on conversations occurring between people inside an office, meeting room or workstation.
It will significantly increase speech privacy and noise control between closed rooms. Though factors such as the conversation’s volume and the rooms’ physical construction (walls, doors, windows, ceilings, ductwork and flooring) also have an impact, low levels of ambient sound are often a design’s biggest weakness, so adding masking results in substantial improvements in closed spaces.
In open plan spaces, the masking effect will gradually increase as distance increases. If you start out relatively close to the person speaking, you may note that dynamic range is reduced, even though intelligibility remains high. As you move further away, you’ll begin to understand less and less of what they say. At some point, you’ll be able to tell that they’re speaking, but won’t be able to understand what they’re saying at all. Move further and their voice will completely disappear below the masking sound.
The distances at which these various effects materialize are dependent not only on the masking sound, but the noise source and overall design.