While acoustic foam cannot stop or block noise from your neighbor’s subwoofer in the middle of the night, it can reduce it.
You might wonder does acoustic foam reduce noise? Acoustic foam reduces noise pollution by removing echoes, and background sounds, not just by blocking the sound but by absorbing it. If you own a school, a home, a restaurant, or an open-plan office, you know that most modern buildings are built with some soundproofing material. They are fitted with acoustic foam or soundproofing panels to reduce background noise.
But how do acoustic foams work? And how are they different from soundproof panels? This article cuts through the noise to answer these questions and tell you all there is to know about foam insulation.
You might also enjoy reading: What is The Cheapest Way to Soundproof a Room?
Understanding The Science Of Sound
If you want to reduce noise coming into your house and enjoy peace of mind, it is vital to understand the characteristics of sound. Sound is a vibration of energy through the air or solid materials.
When sound comes from its source (musical instruments, traffic, construction sites, people’s and animal activities, etc.), it makes objects and air around the sources vibrate.
The vibration is carried in the air as sound waves to your ear. The ear receives the sound waves and begins to vibrate. The brain interprets this vibration as music, speech, or noise.
But since noise is not good for your well-being, you are probably looking for ways to reduce it, if not block it.
Science explains that you can manipulate sound waves using certain materials.
How do materials affect sound waves? When sound energy hits hard surfaces, they bounce back. However, they will likely be muffled or distorted if the waves hit soft surfaces.
It is from this discovery that the concept of sound absorption and sound blocking was born. Let’s discuss the difference between these concepts.
What Is The Difference Between Soundproofing And Absorption?
When noise from the neighbors is giving you sleepless nights, you search for products like sound-absorbing foam, soundproofing foam, soundproofing panels, or soundproofing insulations.
Many think acoustic foams will do the trick because they have an “egg crate-like” form often seen in recording studios and movies. And because recording studios are often quiet, you may reason that acoustic foams will block the outside noise. Well, that is a misconception.
Acoustic Foams Are Used For Sound Absorption
But can sound absorption materials help soundproof a room? No. Acoustic foams do not soundproof or block sound; they can only absorb echo in a room, thus enhancing sound quality.
Understanding the difference between soundproofing and sound absorption will help you make good decisions.
Acoustic foam materials absorb echo to enhance sound quality in a room; no wonder they are used in the walls and ceilings of recording studios as a finished surface.
They cannot block sound, just like you cannot expect sponges to block water. They will absorb the sound but allow it to pass to the other side.
On the other hand, soundproofing materials are often installed inside the wall, floor, or ceiling as part of the building materials. And since they are dense materials, they block the sound by reflecting it into the room.
In a nutshell, soundproofing is where you use dense or heavy material to block sound from getting out or into the room, while sound absorption is where you use soft material as a finished surface to prevent echo and improve sound quality.
So, if you walk into a fancy recording studio with an acoustic foam surface on the inside, know that it is quiet because the studio has added layers of sound isolation materials or mass. The acoustic foam is an addition to help reduce echo, not noise.
Besides absorbing echo, what else does acoustic foam do?
How Do Acoustic Foams Work?
Acoustic foams are porous, lightweight, and softer than sound-blocking materials. When sound hits these surfaces, their open and flexible cell structures help to absorb sound waves. This will prevent noise from reverberating when it hits hard walls, floors, or ceilings.
Acoustic foams convert sound energy into heat, thus reducing sound waves’ ability to bounce back upon hitting a hard object in the room. Therefore, they can be used to enhance music sound within a room.
Recording studios install these foams to create a professional listening environment. The acoustic treatment help musicians produce quality audio and videos.
Although some people think acoustic foams can only absorb sound, they can do more. Here are some things you can achieve with these foams to reduce noise.
1- Reverberation Time
Since acoustic foams absorb sound waves, they shorten reverberation time in the room. Some professionals reason that they can achieve an RT60 of 0.25-0.4s, where RT60 means Reverberation Time 60. It measures the time it takes to reduce sound pressure in a room by 60 dB.
You will notice that most acoustic foams come with a table and an indication of their absorption ability according to the band frequency. This value is often represented by the symbol α (alpha).
For instance, if the foam has an α of 0.7 at 1kHz, it can absorb up to 70% of the sound waves in the indicated frequency band.
The general rule is that the absorption quality of the foam increases with the increase in frequency. You can improve the absorption rate by mounting the foam some distance from the wall.
This trick will enhance the low-frequency performance of the foam. Nevertheless, you will need bass traps to help you target the low frequencies.
Sound-Absorbing Foam Vs. Diffusers
Acoustic foams and panels are made in different forms and shapes, the common ones being pyramid and burl foam panels.
It is easy to confuse these foam structures with diffusers. Diffusers are also acoustic elements, but instead of absorbing sound waves, they are designed to diffuse them.
How do you achieve this? You can place reflective material blocks such as wood irregularly on the foam. When sound waves hit the material, they are scattered in different directions, thus breaking the angle of incidence.
Why should you consider using diffusers if you can solve noise problems with absorbers?
Well, let’s assume you have a small bedroom fitted with acoustic foam for absorbing sound. Your RT60 is probably low; however, you will still deal with direct reflection from the back wall.
Diffusers help you to take care of those early reflections by scattering the sound waves, thus giving the room a more natural feeling.
So, what if you can’t afford to buy acoustic foams?
DIY Alternatives To Acoustic Foams
If investing in acoustic foams is expensive, you can use the following cheap alternatives.
1- Heavy-Duty Blankets
Heavy-duty blankets are excellent alternatives to acoustic foams because they are cheap. If you don’t have used ones in your home, you can buy them in the nearby market at a cheaper price.
However, if you want to use them on the wall, you can hook them like curtains or cover wall surfaces before sticking them.
2- Scrap Materials
You can also use dense fire-treated materials as a suitable sound absorption material to cover the walls. These materials can be fibers, sawdust, and recycled and packing materials.
And since they are dense, they can act as a barrier that reduces the noise passing through the walls.
If you have a home recording studio with adequate physical space, you can isolate the production room from the outside all and fill the space between the two walls with scrap materials.
The materials help to absorb sound that penetrates the inner or outer wall, which means the remaining sound energy can be blocked, thus reducing the noise from or to the studio.
3- Egg-Crate Mattress
These mattresses and covers are made to replicate acoustic foams or egg crates. You can find them from mattress companies cheaply or for free.
Since these companies do not sell old or used mattresses to others, they often tear them down and recycle the metal parts. However, the foam is always thrown away. You can utilize these old mattress foams to absorb sound energy in the room.
4- Egg Cartons
You can also use egg cartons on your home studio walls to improve sound quality. These cartons can be suitable sound-absorbing materials when glued on the concrete wall.
They help to reduce sound reflections from the wall.
What to read next:
The acoustic foam may not block sound from passing through. However, they are used to prevent sound reflection. It absorbs the echo from the sound waves hitting the walls or hard objects in the room.
Since they are soft, they absorb sound energy, thus resulting in high-quality sound production. Recording studios sometimes combine sound blocking and absorption techniques to create a perfect music room.
So, acoustic foams are not ideal for you if you want to block noise from outside or prevent inside noise from disturbing your neighbors.