The Importance of Coverage Area

The most important factor in acoustic treatment performance is coverage area. Or more specifically, the total surface area of all treatments in a room, relative to the room’s size. This relationship between surface area and performance is built right into acoustics test data. One Sabin, the unit of measurement for acoustic absorption, is by definition the amount of sound that would escape (and not be reflected back into the room) through a small, 1 square foot hole cut into the wall.

It’s important to remember this in all acoustic treatment strategies. One example is reverb reduction in an office conference room. The amount of treatments required is a surface area calculation. But let’s take a closer look at one specific application where surface area drives performance.

Most Cost-Effective Performance on Limited Budget

If budget is limited, then generally maximizing coverage area in the room with cost-effective panels yields the best performance per dollar during the first stage of treatments. For instance, in a serious recording or listening room on a small budget, I don't think you can do better, performance wise, than getting as many FlexRange® Bass Trap Panels as possible. The FlexRange® Bass Trap Panel was GIK's first product and it remains one of our most versatile and cost-effective. FlexRange® Bass Trap Panels have 5.5"–9.5" of absorption inside them, which is thick enough to also help with bass frequencies. As such, it's at least a baseline good option in just about any role — corner bass trap, early reflection point treatments for recording or listening, rear wall behind listeners, etc. Certainly, for any one of these roles there are better options, but they cost more. On a limited budget that means fewer panels in the room which won't help performance.

Here’s a good example of what twelve full-size FlexRange® Bass Trap Panels can do for a music room, sent to me from a client who used this exact strategy. The twelve FlexRange® Bass Trap Panels were placed in the corners and at reflection points, something like this:

And the spectrogram performance data showed huge, very obvious improvements. The spectrogram is the “view from 30000 feet” of what your room sounds like. It shows frequency on the X axis, per usual, but the Y axis is decay time. Level/loudness is depicted as color — the red areas are the highest “mountaintop peaks” of the response, and the darker blues are just above the noise floor. Decay times depicted like this give us much more an idea of how the room actually sounds than a simple response graph, mostly because sound is a phenomenon that happens over time. Decay time anomalies in a room are much more audible than response anomalies.

Let’s start with the before treatment:

Here we can see the wildly inconsistent decay times across the board, including several narrow resonances through the bass range from 90-250Hz, and another big resonance at about 48Hz.

As you can see the 12 FlexRange® Bass Trap Panels made a huge improvement:

It’s a ton better! The decay times are much more uniform and consistent across the board. The bass resonances 90Hz and up are dramatically improved, and even the 48Hz decay has improved a bit. These lower frequencies are where we’d get more improvement down the road by upgrading the FlexRange® Bass Trap Panels in the corners to thicker units (like stacked Soffit Bass Traps).

I don’t know of a way to get better results than this without higher budgets. In some cases, if the plan is to build up gradually over time to a superior room, then it might make sense to start with fewer but upgraded panels. But even in these cases, you can always repurpose a versatile panel into another role as you upgrade.

For advice on your specific space, Talk to one of our acoustic experts — it's free.

James Lindenschmidt has been obsessed with audio and good sound since his childhood. He began designing studios more than 20 years ago and has been an acoustics professional for more than 15 years. He started working with GIK in 2016.