Acoustic Foam: What It Is, How It Works & How to Install It

Acoustic foam is an open-celled foam that absorbs sound waves to reduce echo, reverberation and unwanted reflections in a room – and fitting it yourself is straightforward. This guide explains what acoustic foam is, how it works, the main types available, and how to install it step by step.

Are you a musician, music teacher, podcaster, YouTuber or freelance voiceover artist? If so, chances are you want a professional space that offers the best possible acoustic environment, and acoustic foam is an excellent way to prepare such a recording space.

Even if you don't record at all but are an avid listener – say you have a top-of-the-range sound system or a home cinema – you can still benefit from treating your room with acoustic foam to get the best out of your listening environment.

What is acoustic foam?

Acoustic foam is usually made from an open-celled foam that reduces sound waves and their amplitude. The open cells capture the sound waves so they don't rebound off other surfaces and create more noise than necessary, lowering unwanted noise levels. The result is effective noise reduction and noise control.

The most common applications involve attaching it to walls, doors, ceilings and other parts of a room to keep vibration, echoes and noise to a minimum.

Why does acoustic foam matter?

You may be wondering whether it really makes a difference. Several factors affect how sound is experienced in a room – whether you are making a recording or just after the best listening experience:

Reflections

Sound reflects off surfaces, furniture and other objects in a room. How much is reflected depends on the surface – a smooth, flat surface reflects more sound, while softer surfaces absorb some or all of it. That's why a room with soft furnishings, carpets and curtains has far less sound reflection. Acoustic foam absorbs sound rather than allowing it to reflect.

Reverberation

Reverberation is when sound persists in a space after it is produced, because it reflects off the various surfaces in the room, often many times, until the reflections fade. Acoustic foam reduces this by absorbing the sound before it can reflect.

Echoes

An echo is when the reflection of the original sound reaches a listener's ear (or a recording device) shortly after the original sound. The delay depends on how far away the reflecting surface is. As with reflections and reverberation, acoustic foam prevents echoes by stopping the reflections that produce them.

Flutter echoes

A flutter echo is when sound reflects repeatedly between parallel surfaces, often for several seconds depending on the size of the space and the type of surfaces. Acoustic foam is ideal here: treating one or both parallel surfaces removes flutter echoes.

Different types of acoustic foam

Now you know what problems acoustic foam can solve, here are the types that are commercially available and how they are applied:

Tiles and panels

Tiles and panels, also known as sound foam pads, are convenient – particularly the self-adhesive kind – and let you treat specific areas that are problematic for reflections and flutter echoes. See our acoustic foam tiles and panels.

Bass traps

Bass traps are wedge-shaped blocks of foam that fit neatly into corners; you can fit several together in the corners of a room. They are good at absorbing low-frequency sounds, hence the name. See our acoustic foam bass traps.

Sheets

Sheets are convenient and can be bought in rolls of specific sizes, then cut to fit whichever surface you are treating. See our acoustic soundproofing foam sheets.

Cut to size

Acoustic foam can also be cut to your required size and shape, as with other foam types.

All of the above can be bought in convoluted styles (the typical egg-crate or pyramid pattern) or with a flat surface. Convoluted surfaces are designed to absorb more sound than flat ones. For a good example of acoustic foam in a home studio – notice how flat the sound seems once the whole room is treated – see this home-studio treatment video on YouTube.

How acoustic foam works

The science of sound can be complicated, particularly around the travel of sound waves and resonance. For anyone sourcing foam for a professional setting or a personal project, navigating the different types on offer can be tricky – especially when sources talk about the difference between absorbing sound and completely blocking it.

To understand how acoustic foam works, and to select the right foam, it helps to learn the fundamentals of how sound behaves. Put simply, sound is a vibration of energy: when an object such as a speaker vibrates, the air around it vibrates too. These vibrations travel as sound waves, which your ears pick up and your brain processes into something recognisable, such as a familiar voice or music.

Different foams are used to manipulate the shape, intensity and direction of these sound waves, to either absorb their vibrations or block them entirely. Because materials differ in composition, they reflect and absorb sound waves differently – which is where using materials with different surface textures comes in. What you choose depends on the type of room or space you are treating, and why.

If you simply want to reduce the amount of noise in a space, sound-absorbing foam is what you need. It is designed to soften the hard surfaces in a room – a perfect everyday example is a church or other old building with few soft furnishings to rebuff sound waves. Sound-absorbing foam has an open, flexible cell structure that draws the energy out of the sound wave, so less sound is reflected back into the room.

It is worth remembering that sound-absorbing foam can also enhance sound within a space. Wedge or pyramid-shaped absorbing foam can alter sound waves and improve sound quality, which is why it is common in recording studios.

Alternatively, you may want to completely soundproof a space. To fully block sound, foam with a closer-celled structure is most suitable: these foams are denser and thicker, and prevent sound waves from travelling into certain areas. However, completely soundproofing a room is easier said than done – depending on how important it is to fully block sound, this specialist foam may need to be installed within a wall cavity for maximum effect.

Many innovations are under way in the soundproofing and absorption space, including new materials that fully insulate vibrations to block sound from chosen areas – some recent developments even allow sound to travel only one way, an industry-leading achievement.

How to install acoustic foam

Follow these steps to treat your home recording space or studio with acoustic foam:

Step 1: Clean and clear the space

If you haven't already, remove any unwanted items and furniture from the room. Then give it a thorough clean, paying particular attention to the walls and removing any cobwebs, dust and dirt. If you have wallpaper, take care not to damage it.

Step 2: Evaluate the space

Clap loudly in each part of the room and note any reverberations that follow. An empty room will reverberate more and need more significant treatment, since furniture – especially soft furnishings like sofas, cushions and curtains – absorbs sound.

Step 3: Get your materials

Generally, acoustic treatment of a room calls for one or more of three types of acoustic foam:

• Bass traps – these absorb low frequencies.
• Acoustic panels and tiles – these absorb mid-range and high frequencies and are usually self-adhesive for convenience.
• Acoustic foam sheeting – also absorbs mid-range and high frequencies, but covers a larger area or can be cut to fit a specific space. Cut-to-size versions are available, such as the type we sell here, also with self-adhesive backing.

You may also want some general-purpose heavy-duty spray adhesive if needed.

Step 4: Install bass traps

Starting with the bass traps, install these first into the trihedral corners (where two walls meet the ceiling or floor). If more bass trapping is required, add more along the dihedral corners (where two walls meet, or where one wall meets the ceiling or floor).

Step 5: Treat your parallel walls

Apply acoustic panels, tiles or sheeting to the wall behind your recording equipment. If you don't want to cover the whole wall, stagger panels around recording level for maximum effect, then treat the opposite wall in the same way. You may wish to fix them lightly with masking tape first and evaluate the sound again, in case you change your mind before sticking the panels permanently in place.

Step 6: Re-evaluate

Once the room has been treated, re-evaluate it the same way you did before to hear the difference. If there are still undesirable echoes, reverberations or other effects, apply more panels to the problem areas and/or more bass traps until you get the result you want.

eFoam is a leading supplier of foam for industrial, commercial and personal use. If you would like to discuss your soundproofing requirements with a friendly member of our team, please contact us.

Frequently asked questions

What is acoustic foam?

Acoustic foam is an open-celled foam that absorbs sound waves and reduces their amplitude, cutting echo, reverberation and unwanted reflections within a room. It is commonly fixed to walls, ceilings and doors to improve how a space sounds for recording or listening.

Does acoustic foam soundproof a room?

Not on its own. Acoustic foam absorbs sound inside a room to reduce echo and reverberation and improve sound quality. Fully blocking sound from passing through a wall needs much denser, closer-celled material, often built into the wall cavity, rather than surface foam panels.

What types of acoustic foam are there?

The main types are tiles and panels (often self-adhesive, for treating specific problem areas), bass traps (wedge blocks for corners that absorb low frequencies), sheets (for covering larger areas), and acoustic foam cut to size for a specific surface. All are available in convoluted egg-crate or pyramid profiles, or flat.

Where should bass traps go?

Fit bass traps first into the trihedral corners, where two walls meet the ceiling or floor. If you need more low-frequency control, add them along the dihedral corners where two walls meet, or where a wall meets the ceiling or floor.

Can acoustic foam be cut to size?

Yes. Acoustic foam can be cut to your required size and shape, and is also available with self-adhesive backing for easy fitting.