The Science of Acoustic Foam

There’s more to acoustic foam than meets the eye (or ear). On face value, it appears like any other foam, but look a little closer and you’ll find that it’s much more complex.


Acoustic foam helps to dramatically improve the acoustics in your room of choice. It has the inherent ability to absorb a percentage of sound wave energy. This results in a significant reduction of the effects caused by reflections, echoes, reverberation and indirect sound waves. Achieving clarity in sound is simple with SoundFix.

How Does Acoustic Foam Work?


Essentially, acoustic foam acts as a means to reduce the amplitude of certain sound waves. In physics, the amplitude is the maximum distance moved by a point in a sound wave from the equilibrium position. When a sound wave ricochets off a solid surface its energy levels remain the same. This gives it sufficient traction to reach your ears or a recording device. When sound waves hit an acoustic foam panel, a large portion of its energy is absorbed. This significantly improves sound quality as a result.

Understanding Frequencies


Before acoustically treating a room, it’s important for you to understand which frequencies you wish to treat. Various frequencies will be projected within a room, depending on the way in which it is used.
For example, a full spectrum of sound waves are likely to occur inside a recording studio. Because of this, it is advisable to aim for neutral acoustic treatment. By this, we mean acoustic treatment which is capable of dealing with sound waves from low to high frequencies.
We may only need acoustic treatment for certain frequencies if we were treating a conference room, for example.
The graph shown depicts the average decibels of a standard and raised voice. By looking at the graph, we can determine that the majority of energy surrounds the 300Hz to 1500Hz area. In this situation, you would want to seek acoustic treatment capable of dealing with these frequencies.

How Sound Waves Interact With Surfaces


Sound waves can interact with surfaces in a variety of manners. Depending on the type of surface that a sound wave is striking, the following result can differ. There are 4 ways in which a sound wave can interact with a surface. These include penetration, absorption, reflection and diffusion.
Penetration is when a full sound wave or part of the energy from the sound wave travels through the entire surface.
Absorption is when all or part of the sound wave is absorbed by the surface, dissipating within it.
Reflection is when a sound wave ricochets off a surface, sending it in another direction.
Finally, diffusion is when a sound wave breaks apart on an irregular shaped surface. This sends smaller portions of the energy outwards in various directions.
The way a sound wave interacts with a surface is not limited to merely one of these results. For example, acoustic foam is capable of absorbing portions of sound wave energy. If it has an irregular surface (such as a wave profile), the acoustic foam will also actively work to diffuse the sound wave.

What is Direct and Indirect Sound?


Sound waves can be either direct or indirect. A direct sound wave is one which travels straight from the source of the sound (such as a speaker) to your ear. An indirect sound wave, on the other hand, first reflects off one or more surfaces before reaching your ear.
Direct sound comes from the original source. It is the clearest and most accurate sound wave. You can’t completely eliminate indirect sound waves, but by utilising acoustic foam you can reduce the intensity of them.

Low Frequencies Vs High Frequencies


This diagram demonstrates the difference between a high pitch sound wave and a low pitch sound wave. The lines on the diagram demonstrate the frequency of the sound.
Each rise and dip on the diagram represents a wave or vibration. If a sound wave has multiple waves or vibrations per second, the pitch will be higher than one with fewer.
The empty space between each wave depicts the amount of energy contained within the wave. We refer to low-frequency sound waves as bass.
Because bass contains more energy than those of a higher frequency, it is more difficult to contain. We recommend utilising bass traps to contain low-frequency sound waves.

What is a Standing Wave?


When a reflected soundwave and a direct soundwave combine, a standing wave is created. This creates a soundwave with a higher amplitude than normal. The higher amplitude of a standing wave can cause complications during mixing and recording. To combat against this, it is important to install acoustic foam within your recording studio. This helps to decrease reflected soundwaves and improve both live and recorded sound.

The Quarter Wavelength Formula


The quarter wavelength formula is something often used in acoustics and sound absorption. This formula allows you to better determine the optimum positioning and level of acoustic treatment required.
By acoustically treating areas of a room in relation to a quarter of a wave length from the wall, you can raise the effectiveness of acoustic treatment for particular frequencies. This is because there is a state of low pressure and high molecule velocity at the quarter point of the wavelength. Thus, acoustically treating these areas helps to maximise wave absorption. Be aware that this method only corresponds to the wavelength calculated. To create a broader spectrum of sound wave absorption, thicker acoustic material is required.
To calculate a wave length, we must divide the speed of sound by the sound’s frequency. The speed of sound is relatively constant, it travels at approximately 1132 feet per second.
If we’re dealing with a 60Hz wave, for example, then the calculation would be 1132 divided by 60. From here we can determine that this wave is approximately 18 feet in length. This can then be divided by 4 to give us the quarter wavelength which is 4.5 feet.

What Are Primary Reflections?


A primary reflection is a sound wave that has only ricocheted off of one surface before reaching your eardrum. The more times a sound wave bounces off a surface, the more energy it loses. As such, primary reflections pose the greatest threat to your listening experience. By utilising acoustic foam in your desired space, you can eliminate the vast majority of primary reflections which interfere with live and recorded sound.

What Do Acoustic Bass Traps Do?


Lower frequency sound waves (commonly referred to as bass) are more difficult to control than higher frequency ones. Bass has greater levels of energy when compared to its high-frequency counterpart. Bass requires thicker acoustic foam pieces to control. Because bass has a tendency of traveling to room corners, we design our bass traps to fit perfectly there to counteract it. For maximum effectiveness, you can line bass traps along both the length and width of room corners. Corner cubes help to create a seamless integration between bass traps when mounted both vertically and horizontally.

Why Use SoundFix Acoustic Tiles?


SoundFix Acoustic Tiles have an NRC rating of 0.85. On average, this makes them 20% more effective at reducing soundwave energy when compared to many other brands. SoundFix Acoustic Foam Tiles soften hard surfaces such as walls and ceilings. When an indirect soundwave reaches our acoustic foam it’s energy is significantly reduced. This helps to rectify a range of sound quality issues like the ones mentioned above. Browse our full range of acoustic foam and improve the quality of your sound today!

Correct Monitor Positioning


The way you choose to position your monitors will influence the way you perceive sound. This diagram shows an example of the ideal way to position your monitors.
The monitors should be placed in the centre of a room and turned inwards at a 60-degree angle. The space between the monitor and the wall should be consistent on each side. You should be placed between your monitors so that the left and right monitor can perform optimally.
Do not place one monitor closer to you than the other, as this will cause distortion. Similarly, don’t forget to angle your monitors towards you. This way, sound waves travel directly toward your ears, not towards surrounding surfaces.

What are Early Reflections and Reverberation?


Reflections which occur very close together are referred to as early reflections. These reflections tend to occur in smaller confined spaces but can also be apparent in larger rooms. In time, these reflections become increasingly complex and this turns into reverberation. Reverberation effects the quality of sound and so it’s important to prevent reflections from occurring by using acoustic foam.

What is a Flutter Echo?


Flutter echoes occur most commonly between parallel reflective surfaces. They can sometimes be referred to as chatter. Waves rapidly bounce between each surface as they pass the listener. Depending on the size of your room, the flutter echo can be perceived in quick succession or almost as a continuous echo.
By determining paths at risk of producing flutter echoes, you can effectively eliminate them. Technically only one of the effected parallel surfaces requires acoustic treatment in order to prevent this. By softening said parallel surfaces using SoundFix acoustic foam, you can prevent flutter echoes from occurring.

Acoustic Foam Positioning


When mounting Soundproofing Foam, it’s important to understand the dimensions of your room and its layout. Small, medium and large rooms all require different amounts of acoustic foam for maximised effectiveness. It’s also important to take note of vulnerable areas where problems may arise. Parallel walls, for example, may be prone to creating flutter echoes. A flutter echo occurs when a sound wave continuously bounces between two parallel surfaces. Mount acoustic foam to both walls symmetrically to avoid flutter echoes.

Get to Know Your Room Before Acoustic Treatment


Before mounting, take note of areas in your room which are likely to act as primary and secondary reflection points. It may take some experimentation, but once you’ve found the sweet spot, you’re certain to notice the improvements. Understanding the layout of your room is important before making the decision to purchase acoustic foam. By doing so, you’ll have a better understanding of the foam you need to achieve the best acoustic treatment.

How Acoustic Foam is Made


Acoustic foam is a polyurethane foam. Most polyurethane foams are made from 40% polyisocyanates, 50% polyol and 10% water and other chemicals. These are reactive chemicals, so they are blended together by a mixing head to trigger the foaming process.
Once blended, the mixture is poured onto a slow-moving conveyer belt. After moving around 6 ft, the mixture forms into a solid foam block approximately 30” in height. Traveling further still, it’s height will reach around 4 ft. In its present form, the foam is referred to as slabstock.
The slabstock continues along the conveyer belt until it reaches a large horizontal bandsaw. Here, the slabstock is cut into smaller size blocks, which are around 12 ft long. After this, the foam blocks are loaded off and left to cure for approximately 12 hours.
From here, the blocks of acoustic foam can be converted into specialist acoustic treatment products. This is achieved through the utilisation of advanced foam cutting machinery. The proper equipment can consistently produce clean cut acoustic foam tiles, bass traps, corner cubes and other acoustic treatment products.

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