Yelling into the cliffs at the beach or listening to your favourite musician in concert are both fun ways to experience sound and acoustics. But when it comes to managing reverberated noise in the classroom with textiles and acoustic panel solutions there are a couple of key concepts to understand about the function of the materials and where they can be used effectively.

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There are products that Absorb echo within a room, and there are products that will Reflect sound transmission. (some composite panels do a bit of both, but for now let’s keep it simple.)

Echo absorbing materials are used to improve the sound quality and noise levels inside the room in which they are installed. This is where NRC ratings come in. NRC, or Noise Reduction Coefficient, is the amount of sound absorbed by the material. Although there are many complexities around this with frequencies and surface space of the product, 0.4 NRC means approximately 40% of the sound striking that surface will be absorbed, reducing echo and reverberation. These products are usually installed on the walls or ceiling as a finished surface in the room.

Products that are used to block sound are used inside the wall or ceiling – as part of the construction. They can be dense, heavy materials or materials that will separate the wall assembly – and due to their density, often reflect the sound back into the room rather than the sound penetrating through to the other side.

Let’s look at the below scenarios to help understand these principles.

Building an Aquarium with Sponges

To help understand the physics of sound and how it works, imagine you’re building an aquarium to hold water. Would you use glass panels or sponges for the walls of the tank? Clearly a ridiculous question, but it paints a picture of simple physics that applies here.

Sound acts very similar to water when you are trying to control it. If you used sponges for the aquarium, they would absorb the water but quickly let all of it seep through to the other side. Glass and good seals block the water and keep it in place, but the inside of the tank is a very echoey space.

Acoustics and your Squash Game.

Squash is an exceptionally fast game and to keep that ball bouncing as quickly as possible the walls are made of concrete and the floor polished timber. Due to the hard surfaces and small enclosed space, sound in here reverberates for an exceptionally long time – a single hand clap reverberates for 12 Seconds!

Think about sound as a series of bouncy balls for instance. If you throw 100 bouncy balls inside a squash court at the same time, they’ll keep going until they naturally dissipate and stop bouncing, but that will be after some time, as they are able to keep rebounding of every surface they touch. If these balls represent sound, none of that “leaked” through the hard surfaces and was all reflected inwards.

Now picture repeating the experiment with 50mm thick foam lining the ceiling, walls and floor. This time the balls will hit the surfaces and the energy (Sound) from the ball was absorbed into the foam. This means that the “sound” has been stopped in it’s tracks and has stopped reverberating (bouncing) around the room. These sounds, whether voices, music, machines, make up the Ambient sound of a space.

Ok, so how can we best use these concepts?

This Absorption method is an example of the most common acoustic solution for controlling sound reverberation within spaces, while Reflection is the most effective model for controlling sound between spaces. There is a wide variety of acoustic solutions available for schools, and finding out how far you need to go and how to be most effective is the next step!