Does Soundproofing Work Both Ways: The Truth About Soundproofing

When you think of soundproofing, you probably think it only attenuates loud sounds. You’re not alone. And you would be wrong. Soundproofing doesn’t just absorb sound, it can also reflect sound. 

So you have to ask yourself, “Does soundproofing work both ways?”. Yes, soundproofing works both ways. The goal of soundproofing is to reduce the amount of sound traveling from one place to another. That means that it’s not only going to reduce the amount of sound coming in from outside, but also the amount going out from inside.

Making a decision to soundproof your home can be intimidating. There are a lot of products out there that seem like they’d work, but you’re not sure if they will. I’ve done some research and put together a helpful article.

Soundproofing Work Both Ways – What does it mean?

Soundproofing is a process that involves using soundproof barriers to absorb sound as well as reflect it. This is because sound cannot be blocked out completely, or it would become silent. Instead, soundproofing works by stopping the noise by absorbing and reflecting it.

Soundproofing is usually done to reduce the amount of sound that travels between two areas. 

Soundproofing can make a place (such as an apartment) quieter for everyone who lives in it by blocking out sounds that would otherwise travel through walls, windows, or ceilings. So not only will you not hear your neighbor’s music anymore, they won’t be able to hear yours either.

A common example of soundproofing is in a recording studio or a music practice room where you don’t want to get interrupted from outdoor noise and also play loud music without bothering people outside of your room.

Now, you understand that soundproofing works both ways and it mainly depends on the absorption and reflection of the barrier you are using. It’s time to learn about how sound absorption and sound reflection work.

Sound Absorption

Sound absorption is the process of sound waves being absorbed by materials and objects. Specifically, sound absorption refers to the process of sound waves bouncing off an object or material and being absorbed by it instead of being reflected. The more sound that is absorbed, the quieter that area becomes.

Sound absorption is measured on a scale called the Noise Reduction Coefficient (NRC), which ranges from 0 to 1. NRC is calculated using an equation that takes into account how much sound energy is absorbed in a material compared to how much sound energy is reflected back into the room.

Sound Reflection

When a sound wave reaches a surface, it reflects off of it and travels back into the air. The sound wave reflects at different angles depending on the type of surface it hits. 

Hard surfaces reflect sound waves at sharper angles than soft surfaces, which allow them to travel further away from the source. 

Sound Blocking

Another term you may hear frequently in soundproofing is “sound blocking”.

Sound blocking is the ability of a material to prevent sound waves from passing through it. Sound blocking is determined by the density and thickness of the material. A material with a high density and a thick structure will have better sound blocking properties than one that has low density and thin structure.

There are different types of sound blocking materials, but the most common is a material called “Mass Loaded Vinyl”. 

Sound blocking is measured in STC, or Sound Transmission Class. It’s a measure of how effectively sound is kept from traveling through a particular material. The lower the STC, the better your soundproofing will be.

Does Soundproof Foam Work Both Ways?

Does Soundproof Foam Work Both Ways?

Soundproof foam works both ways. It is designed to absorb sound waves and prevent them from transmitting through the walls, floors, and ceilings of a room. You can use soundproof foam to block outdoor noise, as well as noise coming from within the room.

That was the short answer, but here is a more detailed explanation.

The reason soundproof foam works both ways is because it has two different types of layers. One layer is made up of tiny little squares that are each filled with air pockets (like a sponge). This layer is porous, so sounds can travel through it easily. 

The other layer is made up of a denser foam material that blocks out sound completely. This means that when you put these two together, they’ll keep all sounds in or out depending on which way you want them to go (how you hang them).

The Two-Way Soundproofing Myth

When people talk about soundproofing, they often assume that it works equally well in both directions. But in reality, there are two main types of soundproofing: one-way and two-way. One-way soundproofing is designed to block noise from entering a space, while two-way soundproofing is meant to block noise from leaving a space as well as entering it.

Why Two-Way Soundproofing Can Be Challenging

While one-way soundproofing can be quite effective with the right materials and techniques, two-way soundproofing is much more challenging. This is because blocking noise from leaving a space requires a much more comprehensive approach, including sealing off all potential gaps and openings in the walls, floors, and ceilings.

Factors That Affect Two-Way Soundproofing Effectiveness

Even with the most comprehensive soundproofing approach, there are a number of factors that can impact the effectiveness of two-way soundproofing. For example, the type of noise being generated, the layout of the space, and the quality of the soundproofing materials all play a role in how well the soundproofing will work.

Soundproofing both ways – What to know before Buying Soundproofing products

Soundproofing both ways - What to know before Buying Soundproofing products

Since you know the difference between sound absorption and sound blocking, you’ll be able to choose the right materials for soundproofing your home or apartment.

If you’re looking to improve soundproofing both ways, the first thing you’ll want to do is check out the STC (sound transmission class) and NRC (noise reduction coefficient) ratings of the soundproofing treatment. 

What is STC rating

Sound Transmission Class (STC) is a measurement of the soundproofing ability of an assembly, or wall, ceiling or floor. The higher the STC, the better it’s at stopping noise from traveling through it.

What is the NRC rating?

NRC rating stands for Noise Reduction Coefficient. Noise reduction is the ability of a material to absorb sound waves, and the NRC rating is a measure of how well that material absorbs sound waves. 

The NRC rating is measured on a scale from 0-1, with 1 being the most effective at absorbing sound.

Comparison Table

To help you select the best soundproofing treatment for your needs, here’s a chart that can help you understand how well different soundproofing treatments absorb and block noise.

Soundproofing TreatmentSTC RatingNRC Rating
Acoustic Panels30 – 350.9 – 1
Soundproof Curtains20 – 260.7 – 0.85
Mass Loaded Vinyl25 – 350.2 – 0.3
Double Glazed Windows28 – 350 – 0.1
Spray Foam Insulation (With ½” Drywall)35 – 400.7 – 0.8

A low NRC rating doesn’t mean a material is bad for soundproofing. It actually depends on your particular need for soundproofing.

  • If you’re looking to reduce the reverberation or echo inside a room, it’s important to purchase soundproofing materials with high NRC ratings. 
  • If you want to reduce the amount of outside noise in a room, you should look for soundproofing materials with a higher STC rating.

How to Improve Soundproofing both ways

When it comes to soundproofing, there are many ways you can go about it. There are different materials that you can use. 

Here are some of the most common materials that you can use to soundproof the room both ways:

Soundproof Floor Underlayment

Soundproof Floor Underlayment

Soundproof floor underlayment is a great solution for blocking the sound as well as absorbing the sound.

It is important to use this type of material when you are building a new home or remodeling your old one. This product is easy to install and will help you keep your home quiet.

The soundproof floor underlayment can be made of several materials, including rubberized asphalt, foam, or vinyl. Each material has its own advantages and disadvantages.

Soundproofing Insulation

Soundproofing Insulation

Soundproofing insulation is a great addition to your home. It can help reduce noise from outside your house, as well as from inside of it. This means that soundproofing insulation can help keep the peace in your home, whether you’re trying to sleep or just relax with friends and family.

Here are the most common types of insulation:

Spray Foam Insulation

Spray foam insulation is one of the most effective ways to create soundproofing in a home. It’s made from polyurethane, a substance that expands when it comes in contact with air. 

This expansion can be used to fill any gaps between the walls and ceiling, creating a barrier between the inside and outside of your home.

FIberglass Insulation

Fiberglass insulation is made from mineral wool fibers that are coated with a fire-resistant material. 

This type of insulation is used in both residential and commercial buildings. It is particularly good for reducing sound transmission through walls, floors, and ceilings.

Batt & Roll Insulation

This type of soundproofing insulation is installed by rolling it out onto the floor or wall. It’s then cut to size with a utility knife and nailed into place with a nail gun or other tool. 

The batt & roll method is best for large areas like floors, walls, or ceilings. It’s not as easy to install as other types of soundproofing insulation but it does perform well at blocking noise transfer between rooms.

Mass Loaded Vinyl

Mass Loaded Vinyl

Mass loaded vinyl (MLV) is a type of sound barrier that uses vinyl-based materials to add mass to the wall of your room. 

This extra mass increases the amount of sound absorption in your room, making it more difficult for outside noise to get into and through your walls. 

MLV is often used in conjunction with other soundproofing strategies, like adding additional insulation or using acoustic tiles on top of drywall.

Soundproofing Curtains

Soundproofing curtains work by absorbing sound waves and preventing them from bouncing around your home. This means that you’ll have a much more peaceful experience in your home, and you won’t have to worry about hearing things you don’t want to hear.

Soundproofing curtains are made from a thin layer of material that is sandwiched between two layers of fabric to make them thicker and more durable. They’re easy to install and remove, which makes them ideal for people who live in apartments or houses.

Acoustic Panels

Acoustic Panels

Acoustic panels are a great way to improve the sound quality of your room. They work by absorbing sound waves, so that they don’t bounce back into the room and create echoes or reverberations. 

This helps reduce unwanted noise, which can make it easier to hear what’s going on around you.

Acoustic panels can be made from many different materials, but we recommend using foam or fiberglass. These materials are lightweight, durable, and easy to cut into any shape you want. You can use them to cover up walls or create sound barriers between rooms.

Different Types of Soundproofing

Soundproofing works both ways. Soundproofing is a way of reducing the amount of sound that’s allowed to pass through a material. Materials can be soundproofed by adding mass, which increases their density, or by adding dampening materials to reduce their ability to vibrate.

There are four main types of soundproofing, and they’re all pretty easy to implement.

Sound Absorption

Sound absorption is a type of soundproofing that involves the use of materials that can absorb sound. Common examples include foam panels, fiberglass, and acoustic ceiling tiles. 

Sound absorption can be used alone or in conjunction with other methods of soundproofing. When combined with other methods, it can help reduce the overall level of noise in a given space by reducing the amount of sound energy that passes through the walls into an enclosed area.

Sound Reduction

Sound reduction is a type of soundproofing that is used to block the passage of sound through one medium to another. This method does not require any kind of adhesives or sealants, and is used to reduce the amount of noise transfer between rooms.

Sound Reduction reduces the noise levels by absorbing or deflecting the energy. Sound reduction can be achieved through different ways. The most common way to reduce sound is through the use of insulation and soundproofing materials, which are placed between the source of the sound and the receiver.

Adding Mass

Adding mass is a method of soundproofing that involves adding materials to the walls, ceilings, and floors of a room. These materials create more mass in the room, which means there is more resistance to vibrations from sound waves. 

This is great for rooms that are frequently exposed to loud noises, such as recording studios.

The best way to do this is by using Mass Loaded Vinyl (MLV). This type of insulation is very effective and can be used for almost anything.

The reason why it’s so effective is because it has a high density and thickness, which means that it will reduce the amount of sound that enters your room. The best thing about MLV is that it’s easy to install and will help you save money on energy costs in the long run.

Decoupling (Creating Air space)

Decoupling is a type of soundproofing that involves creating a gap between two surfaces that are in contact with each other. This can be done by creating a film or sheet between the two surfaces, or by installing rubber pads between the two surfaces.

It’s called “decoupling” because it creates a gap between two surfaces that are usually in contact with each other. This gap causes them to vibrate independently of each other, so that when the first surface vibrates, it won’t transmit vibrations to the second surface.


Soundproofing is designed to reduce the sound that comes into a room and make it more comfortable for people there. As such, it also reduces the sound that leaves the room and makes it less disruptive to neighbors or others who may be affected by that noise.

Whether you are trying to get rid of noise from the outside or stopping a sound from traveling from a point inside the room, there is no easy answer. 

It is important to note that every material is effective at blocking sound or vibrations at different frequencies and at different levels.

Frequently Asked Questions (Does Soundproofing Work Both Ways)

Does soundproof go both ways?

Soundproofing can go both ways, you can either make it so that the sound inside a room is blocked from escaping, or you can make it so that the sound outside a room is blocked from entering. Either way, you’ll end up with a more quiet space.

Does soundproofing keep noise out or in?

The answer to this question is both. Soundproofing can keep noise out by limiting the amount of sound that gets into your room, but it can also keep noise in by limiting the amount of sound that leaves your room.

It works by creating a barrier between two spaces that absorb the sound and prevent it from carrying through into other areas.

Is one way soundproofing possible?

Yes, one way soundproofing is possible. One way soundproofing is a method of reducing hearing from one direction while increasing hearing from another direction. The most common method of doing this is by installing a wall or door between two rooms.

How does soundproofing a room work?

Soundproofing a room is actually pretty simple. It’s just about creating an airtight barrier between the inside of your room and the outside world. The idea is to keep sound waves from entering or leaving the room, so that you can’t hear what’s going on outside.

Soundproofing usually involves: 

  • Adding insulation to walls, doors, windows, and floors
  • Covering any holes in these surfaces with caulking
  • Covering all exposed pipes with sound-deadening materials
  • Adding additional soundproofing materials to ceilings
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Brendan Ratliff
Brendan Ratliff

As a soundproofing and acoustical professional, I have helped new homeowners, builders and remodelers with their projects. I also help contractors/designers learn how to properly install soundproofing in their clients homes.
I enjoy helping people understand the process of soundproofing and acoustical construction. is a one-stop solution for all of your soundproofing related questions.