If you’re a voice actor, a podcaster, a streamer, or anyone else who deals with recording audio, the topics of soundproofing and acoustic treatment will probably come up a lot. And some may even use these terms interchangeably. But they’re different things, and I’d like to explain the difference here in the simplest terms I can come up with:

• Soundproofing prevents (unwanted) outside noise from coming into your space, and also keeps the sound in your space from leaking out. So if you’ve got problems with passing cars, barking dogs, cicadas, and other noises in your recordings, you need some soundproofing. To achieve this, you need three things (which we’ll discuss below): sealing, separation, and mass.
• Sound treatment keeps the sounds you make inside your space from bouncing all over the place. If your audio is full of echoes, like it was recorded in a large, empty hall, then you need some sound treatment. For this, you need soft, absorbent things. Or clutter. Or both. Another video below should make things clearer.

Soundproofing

As mentioned above, you need three things to soundproof a space: sealing, separation, and mass. And no, foam, diffusers, and all those things you typically see inside a studio don’t play a role here. Soundproofing is usually structural, and it’s practically invisible to most people.

Anyway, before reading ahead, please watch this video from Acoustic Geometry, and then I’ll try to explain things again in the simplest terms I can muster:

Sealing

The first order of business is making your space airtight. Sound mostly travels through air, so you need to take care of any gap, crack, or other path for outside air to get into your space. They used water in the video, but the idea is the same: make sure you plug gaps where outside air can leak in.

At this point, I’d like to point out that some people can get away with just taking care of this: e.g. if you live on an upper floor in a high-rise away from traffic noise, or if you’ve got a large closet or storeroom in a concrete house in a quiet neighborhood. This takes care of faint, distant noise, and some louder, high-pitched sounds.

Separation and Mass

These two items are inextricably linked because they both deal with sounds that pass, not through the air, but through the solid parts of your structure. Sealing can usually take care of many noises, but some things are just too loud (or too low) that they pass through walls and windows. Think of heavy footsteps or knocks on your door, or construction noise, or heavy trucks passing nearby. These things can travel through the structure of your recording space, and stopping that isn’t quite as easy as plugging gaps.

• Mass is easy enough to understand. Paper thin walls will let almost all sounds through, but six-inch concrete walls should block a lot more. You need mass to block sound, and there really isn’t any way around this. It’s physics.
• Separation is about keeping vibrations isolated to certain (i.e. the outer) parts of your structure. This is why studios are usually built like a “room within a room,” and often have double doors. By creating inner and outer structures that can vibrate independently of each other, sound has no way to travel through to your (inner) recording space.

Sound Treatment

While soundproofing prevents outside noise from leaking into your recording space, sound treatment (or acoustic treatment) keeps the sounds you make in the space from bouncing all around. You can skip ahead to 2:06 in the video below (again from Acoustic Geometry) to see the tools we use to treat a space, but I suggest watching from the start to understand how sound works in a room. Then we’ll go over treatment options below.

As mentioned in the video above, you have two basic tools for acoustic treatment: absorbers and diffusers. And while the examples shown in the video are professionally made, there are other options available if your budget is a bit tight.

Absorption

One way to keep sound from bouncing around your recording space (i.e. reflection) is by filling it with things that are soft and fluffy: pillows, comforters, beds, couches, clothes, etc. Some people who are lucky enough to have walk-in closets can record clean audio in there because sound doesn’t get a chance to bounce around – almost all of it is absorbed by the clothes. If you don’t have a walk-in closet, you can build a pillow fort (or a mattress fort), hang thick curtains, build a PVC booth with moving blankets, or basically surround yourself with soft materials.

Diffusion

Absorption is one way to control reflection, and as shown in the video, diffusion is another. Instead of absorbing sound, we can make it bounce in different directions. And while professionally made diffusers are one way to go, there’s another, cheaper less expensive way: clutter. Put up shelves and fill them with toys and knickknacks, books of different sizes, and anything else that can send sound flying every which way but straight back.

The General Idea

The general idea here is to reduce the amount of hard, bare surfaces in your recording space. Keep in mind, however, that you don’t have to pad every single square inch of your walls, or fill your whole room with clutter. You just need to cover specific parts of your room – specifically, parts that can cause sound to bounce back directly to your mic. But that’s a topic for another post.

Recap

• Soundproofing and Sound Treatment are different things. The former is about keeping outside noise out, and the latter is about minimizing echo or reflection in your space.
• For soundproofing, you need sealing, separation, and mass.
• For sound treatment, you have two options: absorption and diffusion.

So, what do you think? Did you pick up anything? Maybe you don’t agree with some of the points here. Say something in the comments.