Soundproofing and Acoustic Treatment – Myths and Realities

With this post, we’re launching the Studio Setup section of our blog. Our goal is simply to clarify the concepts of soundproofing and acoustic treatment (after our experience building our own studio) for all those involved in music and/or music production in an easy-to-understand manner, as we’ve noticed that people often confuse these terms.

If you’re looking for complex solutions or professional assistance for specific needs, we recommend consulting industry professionals and experts. We’d also like to take this opportunity to debunk some myths circulating in society to help music enthusiasts improve the listening conditions in their spaces.

Let’s begin by understanding precisely what soundproofing and acoustic treatment in a room mean.

You’ve probably been in a room with a lot of echo, reverb, or flutter, and you or someone in the room has said, “This room needs soundproofing or is poorly soundproofed.” Or perhaps you’ve been in a recording room or studio, and suddenly an external sound interrupts the session.

You’ve likely thought, “This room needs soundproofing or is poorly soundproofed.” The term “soundproofing” is often used to describe various acoustic-related actions, some of which do not align with its true definition.

What is soundproofing

When we talk about soundproofing, we refer to isolating sound within a specific space. This means and entails two things. Firstly, the sound inside the space cannot escape outside. Secondly, sound from the outside cannot enter the interior. This is the ideal situation every musician and/or producer would want in their studio.

It means not disturbing anyone with the sound of the projects you’re working on and preventing any external sounds from infiltrating your studio and potentially ruining a unique and irreplaceable recording.

This is the situation everyone would desire but not everyone has, as it’s usually very complex (and costly) to achieve. It often involves constructing what’s known as a “box in a box,” which, in simplified terms, means building a room (often using drywall) within another room to prevent acoustic transmission between them by using rubber isolators and other damping materials.

The layer of air between the two rooms (usually partially filled with sound-absorbing material) completes the mass-spring-mass system responsible for isolating or soundproofing the interior room.

Consider this: no matter how well soundproofed a room is, where nothing from the outside can be heard, if its walls are flat and made of sound-reflecting materials (such as concrete, bricks, tiles, drywall, wood, etc.), you’ll have reflections that lead to reverberation, echoes, and resonant frequencies or modes.

These different reflections will add to the original sound emitted by the source and speakers and reach our ears or microphones. The sum of these reflections creates interference in the original signal, altering the recording or listening experience.

That’s why it’s essential to have some degree of control over the acoustics (which involves both soundproofing and acoustic treatment) of your room. In fact, it’s often considered the most critical aspect of a studio. Let’s explore the most commonly used techniques for acoustic treatment: absorption and diffusion.

Absorption

When sound encounters the surface of a different material, it behaves in the following way: a portion of it reflects, some gets absorbed, and some passes through. The distribution of these behaviors depends on the qualities of each material and the frequency being analyzed.

Generally, construction finishing materials (such as concrete, tiles, drywall, etc.) tend to reflect sound predominantly. As mentioned earlier, this leads to a multitude of reflections that can distort the sound and provide an inaccurate representation.

Therefore, one of the techniques used for acoustic treatment is the use of absorbent materials. Certain porous materials, often with specific thicknesses and densities, absorb sound, preventing it from reflecting.

Examples include specific foams, curtains, carpets, glass wool, rock wool, etc., strategically placed (we’ll delve deeper into this topic in a future post) to capture the necessary frequencies.

Diffusion

With diffusion, we can “break up” and distribute reflections more evenly, thus avoiding the formation of modes, echoes, and more. It can also be used to add some liveliness to overly “dry” rooms, creating a bit of reverb. There are various designs and sizes of acoustic diffusers, each acting on different frequency ranges.

Sound Proofing & Acoustic Treatment – Myths & Realities

Let’s attempt to debunk two urban legends related to soundproofing and acoustic treatment, one for each concept. Firstly, regarding soundproofing, we’ve seen and heard many people say, “I’ll cover the entire room with sound-absorbing foam, and that will surely keep the sound from escaping because it’s absorbent!” Wrong! Yes, foam is absorbent, but it’s not soundproof.

Moreover, with shallow depths (like most panels), it only affects high frequencies. In this case, you’d be absorbing sound INSIDE the space, and with extensive coverage, you’d likely have too much absorption in the highs. Not hearing them in your mixes, you tend to emphasize them. When you eventually listen in a neutral space (headphones, car, etc.), you’ll notice that your mixes sound overly bright.

As for acoustic treatment, there’s a well-known myth about using egg cartons. Many people believe that by doing this, they can avoid parallel walls. While this may seem true at first glance, it only works for mid to high frequencies. Lower frequencies have too much energy and easily penetrate egg cartons.

If you overuse them and cover the room with egg cartons, you’ll end up with excessive reflections in the mid and high frequencies. It’s much more effective to, for instance, place a bookshelf with books of different sizes at the rear of your listening area or attempt to build your homemade diffusers.

By understanding the distinctions between soundproofing and acoustic treatment and dispelling common myths, you can take more informed steps to improve the acoustics of your studio and create an environment that enhances your music production and listening experiences.