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An account of an acoustic newbie’s journey from bare walls to a well‑balanced, sonically pleasant space.

The physics of the propagation of sound is immensely complicated, and when the assortment of materials that make up the walls, floors and ceiling (plus any windows, doors and furniture) are added to the equation, it’s very difficult to predict what will happen to sound waves once they’ve left their source. What’s more, every room is different, and it’s not just the dimensions that will dictate how the room will sound… Imagine two rooms of the same shape and size. One has two‑metre-thick concrete walls, and the other a single‑layer plasterboard stud-wall. Even with those brief, albeit extreme descriptions, you probably know already that the two rooms will sound very different. Add in the multitude of room shapes, sizes, wall‑construction methods and surfaces found in home studios, and it becomes impossible to provide a one-size-fits-all guide to acoustic panel treatment.

The subject of acoustics is regularly discussed in SOS, but plenty of readers still ask for the subject to be covered from a much more basic starting point. What follows is a look at installing acoustic treatment from a complete beginner’s perspective: some basic, essential information, along with a bit of advice from acoustics professionals that should give you the confidence to get started. I’ll follow this up by taking you step by step through my own recent experience of treating a room.

Why Bother With Acoustic Treatment?
Untreated rooms have an uneven frequency response, which means that any mixing decisions you make are being based on a sound that is ‘coloured’, because you can’t accurately hear what’s being played. In short, you can’t possibly tell how your mix will sound when played back anywhere else. It isn’t just an issue for mixing, though, because any recordings you make of acoustic instruments will bear all the hallmarks of the space in which you record them. That may be a good thing if the space in question is Ocean Way or SARM West, but probably preposterously bad if it’s your living room or bedroom. So, if you want your mixes to transfer well, and your recordings to be free of room ‘honk’, you need to pay attention to the acoustic properties of your environment — no matter how good the gear you’re using.

First Things First
The first thing to grasp is the outcome you want to achieve. It’s a common misconception that acoustic treatment with acoustic ceilings or acoustic baffles should kill all reverberation, and that you want a room covered floor‑to‑ceiling with foam tiles: this isn’t what you’re aiming for. You also need to bear in mind the limitations imposed by space and budget: most home studios are small in comparison with the Abbey Roads and AIR Lyndhursts of this world, and many home‑studio owners simply don’t have the funds for bespoke treatment solutions.

So what is the aim? Andy Munro, acoustic design specialist, remarks, “acoustic design is the science that restores a neutral sound balance”. Applying that science means interfering with the path of sound to control the sound energy. Jorge Castro, chief acoustician at Vicoustic, says that “in the case of affordable treatment, we need to control the energy of the sound first. Then we can take care of the sound quality. With small spaces, bass frequencies are always a problem, and we should control the low frequencies as much as we can.” In fact, he continues, “In small rooms, I’ve never heard people saying they have too much absorption of low frequencies.”

Absorption & Diffusion: What, Where, Why?
To achieve the right balance, there are two main approaches: absorption and diffusion. Products that have absorptive properties include foam and rigid mineral-wool (see the ‘DIY & Rockwool’ box), and they ‘soak up’ the sound energy, turning it into heat, through friction. Most effective on high‑frequencies, absorption is essential for reducing flutter echoes and for taming bright‑sounding or ‘ringy’ rooms. Bass trapping is also a type of absorption, but is specifically designed to absorb low‑frequency energy. A clever combination of soft, hard, thick and thin materials, including air, is used to make the most efficient bass trap, and an empty gap between the wall and the back of the trap helps to make it even more effective.

Diffusion is the scattering of sound energy using multi‑faceted surfaces. Diffusers are commonly made of wood, plastic, or even polystyrene. Jorge Castro explains: “diffusion helps in energy control and improves the sound quality in frequencies throughout the middle and high range of the spectrum, and also improves sweet‑spot image.” The ‘sweet spot’ is the place between the speakers where you should be sitting to get the best stereo image (imagine that your head and the two speakers form an equilateral triangle). That pretty much concludes the theory: now for the practice!
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