Blog Post

Ian Baker • Feb 01, 2023

How to Reduce Reverberation and Echo with Sound Absorption

The difference between soundproofing and sound absorption

There is often confusion between the difference in soundproofing and sound absorption. In its simplest terms, soundproofing blocks the passage of sound from one room to another, whereas sound absorption is used to improve the internal sound quality of a room by absorbing echo and reverberation within in the room. In turn this helps reduce the volume of the noise within the space but does not help to stop it travelling out of the space. 

Sound Absorption products are used to improve the sound quality within a room. Think of a noisy restaurant, it can often be difficult to hear and have a conversation with the person sat right next to you. That is because these types of spaces are big open spaces and have lots of hard reflective surfaces, wooden floors, high ceilings, large glass windows etc. Couple this with lots of people talking and enjoying themselves at the same time and the noise volume in the restaurant goes up. More sound energy is continuing to bounce off these hard surfaces and stay inside the room for longer. Making the clarity of the sound in the room very poor. 

Sound absorption and soundproofing explained

How to reduce sound reverberation within a room

Absorbing echo and reverberation within a room (sound absorption) and blocking, or reducing sound transfer from one room to another (soundproofing) require different approaches and solutions.

For soundproofing there are 3 fundamentals:

1. Increase the mass (weight) and density of the wall to make it heavier, as mass helps to block sound
2. Decouple the wall meaning one side of the wall doesn't touch the other. Creating a 'room within a room' and isolating it from the existing structure offers the highest level of soundproofing
3. Dampen the vibration energy of the wall

For sound absorption it is about stopping the reflection of the sound energy off the hard surfaces back into the room.

A useful analogy is to think of soundproofing like waterproofing. If you wanted to build a tank to contain water, would you use glass or sponges? A ridiculous question, however, one that allows a visual of how similarly sound acts to water. Sealed glass would block and hold the water. Sponges would absorb the water but quickly let it seep through. Acoustic treatment using sound absorption products are going to absorb the sound, whereas heavy, dense airtight materials will block the sound (soundproofing). 

Echo and Reverberation

Imagine being in a room with hard surfaces, a sports hall, or village hall for example. Clap your hands in a room like this with hard surfaces and the sound appears to reverberate and echo around the space for ages. 


Do the same in a room with lots of soft furnishings and the reverberation is very limited and appears flat, with a very short continuation.


The below video is a great example of this. Have a listen to the differences in the clap being heard in a room without any sound absorption and again following the installation of the ProSound™ Acoustic Wall Panels.

Acoustic Treatment: Before & After Test

Now imagine very bouncy basketballs being thrown around the room. You throw them everywhere, in all directions and they continue to bounce around the room.


Now imagine the walls, floor and ceiling lined with foam. You throw the balls again, only this time they hit the foam and drop to the floor stopping them from continuing to bounce, the energy from the ball has been absorbed by the foam. 


This is no different to a soundwave inside a room, it reflects and bounces off any hard surfaces, but will be absorbed by soft surfaces. This is when the ProSound room acoustic treatment systems are used. They absorb the sound and stop the reflected sound travelling back into the room.


Room acoustics BEFORE installing ProSound™ Sound Absorption Panels

Room acoustics before ProSound sound absorption panels

Room acoustics AFTER installing ProSound™ Sound Absorption Panels

Room acoustics after installing sound absorption panels

Echo in a village hall - case study

If you are reading this blog, it's more likely that you are looking to absorb sound and need acoustic treatment, rather than blocking sound (soundproofing). 
The Soundproofing Store were contacted by 1st Gresley Scout Group, who in their own words, were looking at sound absorption to "deal with a horrendous echo issue."

In this instance it was sound absorption and acoustic treatment, rather than soundproofing which was needed to reduce the echo and overall noise volume in the hall.
In this very real example, it's the same as discussed above. The problem with big halls is that the sound bounces off hard surfaces and continues to reflect and reverberate around the room. This makes hearing very difficult as the sound becomes very "wet" with no clarity to it. The noise volume rises too as the sound energy is staying in the room for longer whilst more sound is being created.  

Sound Absorption wall panels need to be added inside the room, as they are designed to absorb the sound waves, reducing the reflections and therefore reducing the reverberation and echo.
 
People often ask, how many wall panels or ceiling rafts they should use. There is no hard and fast science in terms of how many panels you need or what size etc. It’s a case of the more of the surfaces that are covered, the less echo you will get. However, as a general rule of thumb, look to cover around 25% - 30% of of the wall / ceiling area to achieve a good high level of sound absorption. 
 
Sound Absorption panels come in various shapes, sizes and colours, they can be hung from the ceiling, or fixed onto the walls. This allows for some real creativity and can be used as an artistic feature within the room.

The Solution To The Sound Problem


Mr Barnes the Group Scout leader contacted the Soundproofing Store for advice. Hanging ceiling baffles or rafts were not really an option in this instance, due to ball games being played in the hall and a low ceiling height. Therefore, ProSound™ Acoustic wall panels were added and fixed directly to the ceiling.


It was an ideal solution for their needs as it limited the loss of wall space and ceiling height. They chose a variety of black and red coloured panels to match the "troop colours" of the Gresley Scout Group. 

Sound Absorption Wall Panels 

Sound Absorption Wall Panels

In this instance, ProSound™ Wall Panels, 1.2m x 2.4m (Class A) were used within the hall. They were easily fitted by using Sound Absorption Contact Spray Adhesive and Impaling Clips.

ProSound™ Acoustic Wall Panels Learn More

Did the ProSound™ Sound Absorption Wall Panels Work?

ProSound Sound Absorption Ceiling Baffles
Mr Barnes, the Group Scout Leader, got in touch to tell The Soundproofing Store how delighted he was and what a difference the sound absorption had made: 

"We installed them due to having a real “bounce issue” around the hall. Kids couldn’t hear leaders and leaders really struggled to hear the kids.
Since we installed the sound absorption wall panels, we have had numerous comments about how people can now finally hear each other. One child who wears cochlear implants normally just took them off as soon as they arrived, as they couldn’t hear a thing. They now can!
Another user wears hearing aids and has said how they can now finally understand things that are being said… Honestly it is a real game changer for our site…"

A brilliant result for the 1st Gresley Scout Group and sound absorption reducing the echo within their hall. The Soundproofing Store were delighted to hear it made such a difference to the space, whilst also having such a positive impact on individuals and their enjoyment of the sessions held within the hall.
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"We don’t expect you to become an overnight expert in sound absorption, that’s what we’re here for."

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