And what are the methods to use?

Acoustic treatment is vital to achieving good sound at your event, production in a studio. In this article I outline the main factors to consider and why they matter.

First off, let’s look at the four acoustic phenomenon we are looking to deal with:

• External noise ingress
  This is sound from outside getting in. This can be the noise of traffic, music, tools, construction or any other “ambient” noise getting in. This is a major factor for when filming a TV show, film, recording voiceovers or having an event where quietness is important (such as a conference or wedding ceremony.

• Internal sound transmission.
  This is the sound from inside our venue getting out. This is typically the sound of musical instruments or DJs, typically amplified by a high pwoered sound system. While we might want a loud of sound inside the venue, those outside may not want to hear us. This is particularly applicable for live music performances, dance music events, or corporated events where there are musical “stings” (short, loud pieces of music for stage entrances).

• Echo.
  Echo is simply when sound bounces off a surface and we hear it a moment later. We are all familiar with this when we hear sound “bounce” in a valley or large warehouse.
  Echo usually adversely “colours” sound and makes it harder to hear. If the sound we are listening to is spoken word even a small amount of echo can make it vastly harder to hear. This is particularly true for people who are hard of hearing, or have less high-frequency perception, which generally degrades in most people from teenage years onwards.

• Reverberation.
  This is like echo except that the reflected sound waves interact with each other. Reverberation can be a useful and desirable acoustic tool, such as in cathedrals, as it adds to timbre of the musical content. But the downside is that these soundwave interactions make the sound more complex and therefore harder to interpret. We call this a reduction in “intelligibility”. Achieving good intelligibility is essential to sound reinforcement, especially with spoken word.

In the video below I give a short explanation of these concepts while in the Box7 Soundstage.

Spaces that have a lot of reverberation are called “acoustically live” whereas those with less reverberation are referred to as “acoustically dead”.

An aside on cathedrals; people think that cathedral acoustics are “good” but the reality is that these buildings were designed to maximize the reflection of sound to make the sound as loud as possible for an audience. The reason for this is that they did not have sound amplification systems back then; had they had the kit we have now they would make the space more acoustically “dead”.

All of these four acoustic phenomenon can be mitigated with acoustic treatments.

The products we use absord sound which means that sound that tries to get into a venue is absorbed. Sound that tries to get out is absorbed. Sound that might cause an echo is absorbed and sound that may create reverberance is absorbed. Essentially, it is all about absorbing the sound energy.

By the way, when I say “noise” I am referring to any sound we do not want. Whereas “sound” is the sound we do want.

But where does the sound go?

Sound is transmitted through pressure changes in air - kind of like little shockwaves going through the air. Rather than these pressure changes going through the air, we want to stop them. The materials we use convert the pressure changes into movement of the products we use, at a microscopic level. That energy then becomes heat and is dissipated. In energy (watts, Joules, BTUs etc) the amount of energy in sound is tiny and you would not feel heat from it, but it is there.

There are a lot of ways of absorbing sound to stop unwanted transmission, echo and reverberation.

Our go-to methods include:

• Black wool serge.
  This is a drape product we have thousands of square metres of. It is relatively easy to rig (using truss, catinery lines, existing rigging or “softscene”) and really effective in absorption of mid and high frequencies. Using two or three layers of this fabric spaced apart can be sufficient for creating “rooms within rooms” and prevent sound transmission between conference spaces.

We have also used this in aircraft hangars, warehouses and tunnels to reduce reflections. It has also been used at arena venues to reduce “slap back” echo.

• Blokka Panels.
  These are our own product which we developed to prevent external sound transmission. I.e. sound from inside getting outside. This is particularly relevant for events with high sound pressure levels, such as dance music or concert events. Blokka panels are best used in conjunction with black wool serge.

• Proper sound system design.
  This is typically the most important part of an acoustic system. All to often people put in large sound systems by a stage, which has to be very loud to give coverage of an audience area. The problem with this approach is that the louder the system is the more reverberance is produced.

Using methods like distributed system and time-delays removes this issue, gives greater intelligibility, and means lower acoustic energy in a space.

I love audio because I enjoy sound.

It has always frustrated me that most “sound engineers” only think about the sound equipment. Whereas I believe that the sound experience is impacted by the audio equipment and room acoustics. As sound engineers we can affect both of these, indeed it is our responsibility to do so.

In 2023 I built the Box7 soundstage. This is a space where sound proofing and acoustics are essential as people are making films and tv shows in it. It was a delight to design and build our own acoustic solution for this space. What I did here was use wall insulation material but left it exposed so as to absorb as much reflection as possible. In addition the venue has restratable wool serge drapes, often doubled-up in spaces.

As an acoustically sensitive person I really enjoy being in this space.

If you are having challenges with acoustics or sound in your venue or event please do get in touch for a chat. We love puzzles and a challenge! And we are also keen to support with provision of drapes, Blokka panels and rigging to sort acoustics. Better still we can provide a complete acoustic and audio solution to your project.