Does Rigid or Foam Board Insulation Block Sound?

I’m sure we’ve all had the urge to play music on full blast in our rooms. However, this isn’t always possible to achieve without bothering other people throughout the house. You might be wondering whether or not foam board insulation might be the perfect solution for your musical dilemma.

Foam boards don’t block sound since they’re very lightweight and porous, which means they can’t stop sound waves from passing. However, foam boards are excellent sound absorbers to prevent sound reverb and bouncing.

Does Foam Board Insulation Block Sound

The rest of this article will tell you everything you need to know about foam boards in regards to sound insulation, so you can better understand the way it works and make an informed decision to fit your own musical needs.

Why Doesn’t Foam Board Insulation Block Sound?

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Foam board insulation isn’t the best option for soundproofing a room, even if you cover the entirety of the wall. This is because foam is porous and therefore lets sound pass through the material.

An example of foam’s ability to let sound pass through can be found in old speakers and earphones, which used foam as covers or earphone cushions. These devices worked perfectly with foam because foam doesn’t block sound at all.

For blocking sound, you need a substance denser than foam. Foam absorbs sound rather than blocking it. To understand this, it’s crucial that you realize the difference between sound absorption and blockage.

Blocking Sound vs. Absorbing Sound

Blocking and absorbing are completely different things in terms of sound. Depending on which option you’re trying to achieve, you need to use different substances.

When a material absorbs sound, this means that it prevents the sound from echoing and bouncing in a room. Sound absorbers trap sound waves and convert them into heat so that fewer waves pass through. Sound absorbers are usually porous and spongy like foam.

However, sound absorbers can’t be used to block sound. For example, thermoplastics are good thermal barriers but poor sound barriers. Although sound-absorbing, they don’t have the mass to be effective acoustic panels.

On the other hand, sound blockage aims to prevent sound from passing through a certain material. To achieve this effectively, you need to use denser materials than foam.

Applications of Foam Insulation

If foam insulation isn’t an effective option for sound blockage, what other applications does this material offer?

As I mentioned earlier, foam boards are sound absorbers that prevent sound reverb and bouncing. They can be very useful in big buildings and open areas like gyms and salons.

When a sound is made, it travels through air and continues until the energy drops. If there’s a surface on its way, like a wall, ceiling, or floor, the sound waves will hit it and bounce right back and continue until they lose energy.

The stronger the surface is, the more efficiently it’ll push back sound waves. That’s why our voice echoes in big empty buildings. Heavy reverbs reduce sound clarity, and that’s when sound absorbers like foam boards come in handy.

How To Make a Room Soundproof

We’ve learned that foam boards aren’t the best option for sound blocking. But what are the alternatives?

Install Soundproof Materials

Installing soundproof materials is a great way to block excess sound from exiting a particular room. Here are a few examples of good sound-blocking materials:

  • Mineral wool
  • Fiberglass
  • Spray foam insulation

Let’s discuss these options in greater detail.

Mineral Wool

Mineral wool insulation is lightweight with improved thermal and acoustic properties. The dense nature of mineral wool inhibits heat and cold movement through floors, walls, and even ceilings. Additionally, it absorbs noise, vibration, and impact.

Made of a mixture of mineral wood and glass wool, it features 95% sound absorption and an NRC of 1.05 for improved sound dampening and reduction.

Adding mineral wool to the walls will minimize sound transfer between rooms and reduce feedback and echo, which can increase overall sound quality.


Fiberglass is a porous material composed of melted plastic that has been spun into wool and bolstered with tiny glass fibers. It’s a classic for temperature-related insulation, but it also helps absorb sound like mineral wool.

When standard 3-1/2 inch (8.89 cm) thick fiberglass batts are used in the wall cavities, the STC rating can be raised from 35 to 39. And the sound is further reduced as it travels through the walls.

Spray Foam Insulation

Spray foam is a highly effective option for sound insulation. It creates an airtight seal that keeps noise trapped in the room while simultaneously dampening outside noise.

This alternative has an advantage over mineral wool and fiberglass because spray foam has the ability to cover crevices in the wall, which the previous options cannot achieve. This is because wool and fiberglass are solid materials.

However, it’s important to note that this option is not as effective as mineral wool and fiberglass because spray foam isn’t as dense. Spray foam is generally used for mild sound blockage while mineral wool and fiberglass can completely block noise.

Consider Insulation in House Construction

A building’s insulation system is designed to reduce airflow through the walls. Reduced airflow dampens and blocks sound. Insulation with a higher R-value usually does a better job of stopping air from moving through the wall and reducing sound.

For soundproofing exterior walls, use gaskets and foam around doors and windows.

Another area where sound can be transferred from outside into or between rooms is where floors, walls, and ceilings intersect. If you want to minimize the transfer, discuss it with your house builder to find solutions. One way is viscoelastic damping.

You can install thicker drywall, double-layer drywall, or dampened drywall for interior wall surfaces. Compared to regular drywall, damp drywall is dense and better at soundproofing.

Lastly, our recommendation is to do your research. Learn about NRCs and STCs, ask your house builders and people with knowledge to optimize your soundproofing journey.

Here’s a video showing some sound blocking tips you can accomplish at home:


Foam board insulations can provide thermal insulation, but the material isn’t heavy enough to serve as a sound-blocking panel. However, it does help reduce bounce and echo in enclosed spaces, which can improve sound quality.

It’s possible to block sounds completely by using denser materials like mineral wool and fiberglass that prevent or reduce noise transmission. They’re usually installed in ceilings, floors, walls, and even doors to absorb sound and prevent it from entering or leaving a room.


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