GB Foam Direct - Sound Guide
By understanding the way in which sound works in your room, you’ll be able to benefit the most from your acoustic foam. The diagrams below outline such topics as reflections, reverberation, direct and indirect sound, flutter echoes and more.
Determining Required Frequencies for Treatment
Depending on the type of room you’re working with, you may not need acoustic treatment for a full spectrum of frequencies.
If for example, you were to treat a recording studio, it is fair to assume that you would require treatment across a broad range of frequencies.
Take something like a lecture room though and you may not need as much acoustic treatment.
From this graph, you can see the decibels of a raised tone voice and a normal tone voice in a room. If we analyse the data, it is clear that most of the energy is contained within 300Hz to 1500Hz. A room such as this would benefit most from acoustic treatment which can control frequencies within this range.
Sound Waves & Surfaces
Depending on the type of surface a sound wave is striking, it will interact with it in different ways. Acoustic foam, for example, is designed to absorb a portion of sound wave energy. They are also commonly shaped in a way which helps to diffuse the sound wave.
The ways in which a sound wave can interact with a surface are as follows - Penetration, Absorption, Reflection and Diffusion.
When a sound wave passes through a surface it has penetrated it.
If a sound wave dissipates inside a surface it has become absorbed.
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 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.
What is Direct and Indirect Sound?
When a sound wave travels straight from the source to your ear, we refer to that sound wave as a direct one. Alternatively, an indirect sound wave is one which ricochets off one or more reflective surfaces before reaching your ear.
Ideally, sound should be heard in a direct fashion, however, it is not possible to eliminate all indirect sound waves. Through the use of acoustic treatment though, you can reduce the energy contained within indirect sound waves. This will inhibit their ability to travel to your ears, thus improving the quality of sound.
Low Frequencies Vs High Frequencies
Take a look at this diagram. Here you can see the difference between a high-frequency sound wave and a low one (bass).
High-frequency sound waves contain more vibrations, which is depicted by multiple inclines and declines. Bass contains less of these but are filled with more energy. The empty space between the incline and decline is a depiction of energy.
As you can see, there is much more energy in a low-frequency sound wave. Because of this, thicker pieces of acoustic foam (such as bass traps) are required to contain them.
What is a Standing Wave?
A standing wave (otherwise known as a room mode) occurs when a reflected soundwave combines with a direct soundwave. This tends to occur when one or more of the rooms dimensions is a direct multiple of a sounds wavelength. If two waves are of the same frequency they are said to be in-phase. The result, we will hear both waves at the same frequency, but as they are combined they will have a higher amplitude.
The Quarter Wavelength Rule
This is an effective method for better determining the optimal placement of acoustic treatment.
The quarter wavelength rule is a popular method applied to work out the quarter point of a sound wave. By acoustically treating areas at this point, you can maximise the efficiency of your acoustic treatment.
Remember that this calculation helps to determine the quarter wavelength of a certain frequency. If you wish to treat multiple frequencies, thicker acoustic material will be needed.
Calculating the length of a sound wave is simple. All you need to do is divide the speed of sound (approximately 1132 ft per second) by the hertz of the sound.
As an example, to calculate the wavelength of 60Hz you would divide 1132 by 60. This would give you 18. Thus, you can summarise that the wavelength is approximately 18-foot-long. Divide this length by 4 to determine the quarter wavelength measurement.
What are Primary Reflections?
Primary reflections are sound waves which ricochet off one reflective surface before reaching your ears. If your room is not properly treated with acoustic foam, you are likely to experience significant sound interference. This is because these early reflections still contain large amounts of energy. Our acoustic foam helps to soften vulnerable surfaces and reduce the energy contained within the sound wave.
What are Early Reflections and Reverberation?
In a smaller confined room, 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. Even in larger recording rooms however, 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 continuously bounce between two solid parallel surfaces, a flutter echo is created. Depending on the space between each parallel surface, the flutter echoes can be either interpreted as a continuing echo or in quick succession.
By softening at least one of the parallel surfaces at risk of creating a flutter echo, you can prevent them from occurring. The best way to do this is by mounting acoustic foam to this surface.
Positioning Your Monitors
Did you know that the position of your monitors can affect the quality of your sound?
Ideally, you should be stationed in the center of your room. 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.
Why Use Acoustic Tiles?
We can utilise the properties of acoustic foam to absorb great deals of energy at reflection points. In this diagram, you can see how the energy of a primary reflection is reduced when using a 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 the acoustic tile.
Why 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.
How Acoustic Foam is Made
Like many other types of foam you may be familiar with, acoustic foam is a polyurethane foam. These types of foam are usually made from 50% polyol, 40% polyisocyanates and 10% water/other chemicals.
All these chemicals are reactive to each other. As such, they must be blended together inside a mixing head. This is what helps to kickstart the foaming process.
Once the chemicals have been mixed together, they are poured onto a conveyer belt. This conveyer belt moves at a slow speed. As the mixture moves along the conveyer belt, it begins to rise forming a long block of 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 horizontal bandsaw which cuts the slabstock into smaller more manageable blocks of polyurethane foam.
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 for conversion. Here the foam is cut using specialist equipment. It is made into a variety of acoustic treatment products which you can use in your home or place of work.
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