Everything You Need to Know About Acoustic Foam for Soundproofing
Understanding how acoustic foam affects sound, is integral to creating a space with optimal acoustic treatment. Often referred to as soundproofing foam, you may be surprised by the way acoustic tiles and bass traps manipulate sound waves. That’s exactly why we’ve created this in-depth guide explaining everything you need to know about acoustic foam for soundproofing.
What is Acoustic Foam?
Acoustic foam isn’t too dissimilar from many other polyurethane foam types you might be more familiar with, including those inside your furniture. Thanks to its compositional structure, open-cell polyurethane foam can be an excellent material for absorbing sound wave energy, with the potential to dramatically improve the acoustics inside any designated room.
How Acoustic Tiles & Bass Traps Are Made
As we’ve discussed, acoustic foam is a specific type of foam called polyurethane foam. This is usually made from 50% polyol, 40% polyisocyanates and 10% water/other chemicals. All these chemicals are reactive to each other, so when they’re blended inside an industrial mixing head, the foaming process begins.
Once the chemicals have been mixed, they are then poured onto a slow-moving conveyor belt. As the mixture moves along, it begins to rise forming a long block of polyurethane foam. At this stage, the foam is referred to as slabstock.
The slabstock continues to move slowly along the conveyer belt, still rising as time passes. Eventually, it meets a bandsaw which cuts the slabstock into smaller blocks.
From here, these blocks are unloaded and left to cure for around 12 hours. Once the foam blocks have had enough time to cure, they can be sent to a foam converter. The blocks are then made into various types of acoustic products such as panels, bass traps and corner cubes to be used in recording studios, construction projects, rehearsal rooms, offices and much more.
Most people are familiar with seeing acoustic foam in a classic grey colour. Whilst this is the most common colour for these sound treatment products, acoustic foam can come in virtually in colour. For example, here at GB Foam Direct, we stock acoustic foam in grey, red and blue as standard; we even have specialist, high fire-resistant soundproofing tiles in true black, which is far less common.
How Soundproofing Foam Works
Although acoustic foam is commonly referred to as soundproofing foam, it’s not strictly a soundproofing product. Whilst sound wave energy is absorbed within the foam, it doesn’t entirely block sound from travelling through it. Instead, its primary function is to inhibit the way indirect sound waves travel around your room. To properly understand how acoustic foam manipulates sound waves, it’s a good idea to familiarise ourselves with various sound terminology.
Understanding Frequencies
Some rooms require different levels of acoustic treatment. That’s why it’s important to understand the range of frequencies which you’ll be dealing with in a given room. Professional recording studios, for example, deal with frequencies across a wide spectrum. As such, a room like this would require acoustic treatment that can deal with frequencies from low to high.
Take a look at this diagram. It shows the average decibels of a raised and normal tone voice. A classroom or conference room is a good example of a room where you may hear noise like this. As you can see from the diagram, the largest proportion of energy is situated from 300Hz to 1500Hz. Because of this, it would be wise to seek acoustic treatment which is capable of dealing with frequencies in this range.
What is Direct and Indirect Sound?
Sound waves can be either direct or indirect. Direct sound travels straight from the source of sound to your ears. Indirect sound first reflects off of one or multiple surfaces before reaching your ears. These reflection points are usually walls, which is why we soften these surfaces with acoustic tiles.
Direct sound waves are the generated noise in its purest form, so these are the ones we want to hear the most. Indirect sound waves cause interference, creating noticeable things such as echoing. When we strategically place acoustic panels on vulnerable reflection points we are reducing the indirect sound waves’ ability to travel. This is because the acoustic foam absorbs a portion of the energy contained within the wave, meaning it’s unable to reach the ears of the listener in its indirect form. As well as walls, acoustic tiles are often affixed to ceilings to further
By installing acoustic foam in your room of choice, you can reduce the severity of indirect sound waves whilst keeping direct sound waves consistent. This results in clearer, uninhibited sound; creating a room that’s much more suitable for creating live and recorded sound.
Low Frequencies Vs High Frequencies
Low frequencies contain fewer vibrations than higher frequencies. If we were to depict a high-frequency sound wave with a moving line, we would note that it has multiple high-climbing peaks and steep dips (waves). A low-frequency sound wave, on the other hand, would have significantly fewer waves. They would not climb as high and would be a lot less steep. Sound Wave frequencies behave differently depending on whether they’re low or high, not only do they sound different, they travel around your room differently. For example, low-frequency sound waves (or bass) tend to travel towards room corners, that’s why we use bass traps to deal with them.
What are Primary Reflections?
When a sound wave initially strikes a reflective surface, it turns into a primary reflection. These sound waves, having bounced off of just one surface, retain most of their energy, making them the primary culprits for sound interference. You can mitigate this interference by mounting various acoustic foam products around your room.
Sound Waves & Surfaces
Depending on the type of surface a sound wave is striking, it will interact with it in different ways. Acoustic foam tiles, for example, are designed to absorb a portion of sound wave energy. They are also commonly shaped in a way which helps to diffuse the sound wave.
Sound waves can interact with a surface in various ways, including:
- Penetration: When a sound wave passes through a surface it has penetrated it.
- Absorption: When a sound wave dissipates inside a surface it has become absorbed.
- Reflection: A reflection is when a sound wave bounces off a surface and travels in a new direction. This can happen multiple times depending on the amount of energy the sound wave contains and the potential for reflection.
- Diffusion: Diffusion occurs when a sound wave strikes a surface which is not flat. In this instance, the sound wave breaks up into multiple parts and travels in various directions.
Quarter Wavelength
We use the quarter wavelength rule to determine the optimum placement of acoustic treatment. This is because sound waves are at the most vulnerable at the quarter measurement point. To determine the quarter wavelength of a sound wave we must use the following calculation.
First, we must divide the speed of sound (in ft) by the Hertz of the sound. Sound travels at approximately 1132 ft per second. If we were attempting to treat frequencies of 60Hz, we would divide 1132 by 60. This would give us 18. After this, we simply divide 18 by 4 to determine the quarter wavelength.
What are Early Reflections and Reverberation?
In smaller, confined rooms, reflections are usually so close together that we cannot perceive them individually; we call these early reflections. The effect because of this is commonly referred to as reverberation or “reverb” for short. However, even in larger rooms, this effect can still take place. Eventually, sound reflections will evolve into reverb as they become increasingly more complex.
What are Flutter Echoes?
When sound waves get caught between two solid parallel surfaces, a flutter echo can be created. This causes the sound wave to continuously bounce between the surfaces, passing your ears each time. We can prevent flutter echoes by acoustically treating at least one of the parallel surfaces. This softens the surface, thus preventing the sound wave from rebounding.
Positioning Your Monitors
Did you know that the position of your monitors can affect sound quality? When using monitors, ideally you should be stationed in the centre of your room and your monitors should be placed equidistant on either side of you. They should also be angled inwards towards you at a 60-degree angle. This helps to ensure that your monitors project sound waves which travel directly to your eardrums.
When To Use Acoustic Tiles
We can utilise the properties of acoustic foam to absorb great deals of sound wave energy. In this diagram, you can see how the energy of a primary reflection is reduced when using a SoundFix acoustic foam tile. The left ear receives much more energy than the right ear does. With an NRC rating of 0.85, as much as 85% of sound energy is absorbed by this acoustic tile.
When To Use Bass Traps
Low frequencies or bass contain much more energy than mid to high-frequency sound waves. As such, thicker acoustic foam is required to absorb low-frequency energy.
Bass traps are an ideal way of managing unwanted low-frequency sound waves which cause sound interference. Bass is much more likely to become trapped in room corners and reflect between the surfaces. Our precision-engineered bass traps prevent this and are available in a range of colours to suit your preference. We also stock matching acoustic corner cubes which, when used in conjunction with bass traps, can fully acoustically treat the corners of your room.
Speak to Our Acoustic Foam Experts
Whether you need acoustic treatment to assist with music production or stylish acoustic solutions for interior design projects, our team of experts will be happy to assist you. We stock a comprehensive range of foam products for sound treatment in many different shapes, styles and sizes.
All of our soundproofing foam products are professionally manufactured using high-precision CNC cutting machinery and are made using the best quality polyurethane acoustic foam. What’s more, we offer next working delivery across many areas throughout the United Kingdom. Call 01494 441177 or email sales@gbfoam.com.