When we want to treat sound issues in a room, it might not be clear if we want to “Improve Acoustics” or “Soundproof” the room. Those are two different fields. Each one treats different issues and has different solutions. Let’s dig into that.

What is soundproofing

Soundproofing is a set of means to prevent sound from getting into a room or escaping from it. There are some key principles to understand for effective soundproofing. If you think covering egg cartons on all your walls is one way to soundproof your wall, you might be wrong.

In short, here are the 4 main principles of soundproofing:. 

• Blocking. A heavy and thick material can block sounds. The thicker and heavier, the better the blocking capacity.
• Damping. Imagine hitting a small bell, it will keep ringing for a few more seconds. But if you put your hand on it, the sound will stop. This is the damping effect. Some materials can be installed to play the role of the “hand”.
• Absorbing. Porous materials have the ability to reduce sound’s amplitude by converting sound’s vibration into heat. They are generally installed in wall cavities to reduce resonances in the cavity.
• Decoupling. If two hard surfaces are in contact and you knock on one, the sound will travel from one surface to the other. Putting a material or space in between, will prevent sound from traveling that easily. This is called decoupling.

Soundproof walls, ceilings, and floors include those 4 principles to isolate sound from one room to another.

What defines a room’s acoustic

A room’s acoustic is how the sound travels within a room. Picture yourself in a room without any furniture. All the walls are made of concrete. If you start to shout you should hear your own voice kind of echoing or reverberating. The soundwaves of your voice bounce on everywhere and amplify the sounds. Some of these bounced soundwaves will come back to you, that’s why you hear your voice all funny.

Echo or Reverberation

Echo is a single reflection of the sound on a hard surface. It’s exactly the experience of you shouting in the Grand Canyon and listening back to your voice. Reverberation on another hand, is the superposition of reflected sounds. It distorts the sound heard from your voice and make it harder to comprehend.

Does Echo / Reverberation matter in acoustic?

Acoustic-wise, echo or reverberation are definitely phenomena we want to avoid. In rooms where acoustic is essential such as movie theaters, concert halls or recording studios, you might have noticed foamy or soft materials covering the walls. Their purpose is to reduce the reverberation or echo in the room.

Soundproofing: The common ground

As mentioned above, porous materials are necessary to prevent soundwaves from bouncing on walls. This type of material offers absorption properties. But they lack all the other soundproofing principles: blocking, dampening and decoupling.

So does a recording studio only need soft materials for good acoustic?

The answer is no.

An efficient acoustic room has to be soundproofed from outside noise. That’s why the walls of acoustic rooms such as movie theaters are thick and heavy. Next time you queue to see a movie, pay attention to the wall thickness of the projection room. There is a high chance that those big walls include materials such as foams, decoupler, damping compound to effectively soundproof the room.

In short, soundproofing is necessary to have an efficient acoustic room. But a soundproofed room does not necessarily have excellent acoustics.

To soundproof or to improve acoustic?

Identify the source of discomfort

If when watching TV the source of discomfort comes from the neighbor’s lawn mower, you might need to consider soundproofing your room. 

However, if you clap in your hand and hear a metallic-ringing sound resonating, it should come from reverberation. It means that the surface of your wall allows the sound to bounce. It may be time to consider increasing their absorption effect.

Install absorbing elements

As said above to reduce reverberation, you have to install absorbing elements. The first that comes to mind are acoustic foams or bass traps. I would suggest not to rush to these options unless you plan on making a recording studio.

There are common items that are already part of our daily life that should do the tricks. Curtains (the thicker, the better the absorption), plants, and furniture are simple ways to deal with those reverberations.

If you plan on building a home cinema, or a recording studio, then consider using acoustic foams and bass traps. It might bring you more sound control than furniture.

A good rule is to cover around 20 to 25% of walls for better acoustics. This number can vary depending on the configuration of your room. Bass traps are most effective where the sound reverberation is at its peak. This means in the corners of the room.

I need to soundproof, where should I start

Unlike acoustic improvements, soundproofing often requires modification to the wall composition. The principles of blocking, absorbing, dampening, decoupling have to be integrated in your wall. This is done by adding materials and basically changing the nature of the wall. The same applies to ceilings, floor or even windows.

So bear in mind, that if you need to go this way, it might be more work than just buying some foam and hanging it on your wall.

Final Thoughts

Soundproofing and Acoustic improvements are two different practices. Once this is clear, you should identify what bothers you. Solving room acoustic’s issues are not that complex for a “standard” room. Simply furnishing your room should be enough.

However, if what you need is soundproofing, it might be a bit more complex. I’ll proceed the following way. First, identify the nature and source of noise. Then, look for the noise path. Finally, define what of the four principles is lacking and should be applied.

About The Author: Ludovic Chung-Sao. Ludovic is founder of Zen Soundproof. He uses his experience as a Mechanical Engineer to compile Soundproofing DIY guides. His technical experience and natural curiosity help him break down complex topics to make it clearer for others. He also finds inspiration in sharing mindful habits. Learn more at Zensoundproof.com!

Photo by Wes Hicks on Unsplash