Acoustic Treatment

Author: Brad   Date Posted:3 September 2019 

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What is acoustic treatment and why do I need it?

 

Sound recording

So you’ve got yourself a nice microphone, a great vintage sounding preamp, expensive studio monitor speakers… but you’re recordings still don’t sound quite right?

Most people underestimate the importance of acoustic room treatment.  Sounds waves are similar to light waves in the sense that they reflect off surfaces.  Your room is filled with hard surfaces, commonly known as walls.  Once the sound waves comes out of your speaker and hits the wall it bounces off that wall and results in a build up of frequencies or something known as flutter echo, this is the high frequency slap back sound you’ll hear if you clap your hands in an untreated room.  If the room is untreated you might end up getting these sounds recorded back through your microphone.

Home theatre

The rooms in our homes are generally not designed with acoustics in mind.  Most rooms are boxy with hard sharp corners that are not great for acoustic sound waves.  Home theatre sound systems these days are amazing, you can spend a lot of money on them, so investing that little bit more to make sure your room sounds the best it can, so your speakers can sound the best they can.  Simply getting rid of those flat surfaces and putting some bass traps in the corners of your room can get rid of all those nasty deflections so the only audio you hear in the room is the sound of your speakers…. Or someone eating popcorn.

 

Types of acoustic treatment

 

Absorption

Acoustic foam that comes in the form of 50 x 50 x 5cm panels is your bread and butter for treating your space.  Being of high density, measured in kg/m3, the density of the foam is worked out by the weight of the liquid used to make every metre cubed of foam.  The foam panels absorb a lot of the sound waves bouncing around.  Absorption panels are perfect for big flat walls and getting rid of those high end reflections you can hear.

 

 

Diffusion

Sound waves can build up!  Sometimes you don’t want to completely get rid of all that sound because its nice to have some sort of live “normal” feel to a room without it sounding completely dead and muted.  Diffusion panels are perfect because instead of the sound waves building up and creating hot spots in your room the diffusion panel with give an uneven surface dispercing the sound waves, keeping the sound waves there, but spreading them out a bit more.

 

 

 

Bass traps

Bass traps are designed to trap certain frequencies, "bass frequencies".  Low end waves tend to build up in corners which can create a boomy sound.  By putting some bass traps in the corners you can absorb some of that low end energy.

 

 

Where to put it and how much to use

There is a real science to acoustic treatment, most of us aren’t scientists, but there are a few tips and tricks you can use to do it yourself and get some good results.

Firstly, stand in the middle of your room and clap (on beats 2 and 4 not 1 and 3, you know the rules!).  This is going to be a good test to find those flutter echoes, the high end frequencies in your room.  Usually up in the high corners of your room or off a large flat wall.

Put some music on and have a walk around your room.  Poke your head into corners and sit down where you would normally sit.  You’re listening out for boominess or frequencies and sounds that are harsh.  If you put your head into a corner and your head almost explodes from the sound of bass, you may need a bass trap in that area.

Secondly, if you’re in a recording studio setup, specifically treating your room for mixing, sit in the position you mix in.  Get a friend (or your mum if you don’t have any friends) to run a mirror over the walls next to you, once you see your speaker in the mirror this is the spot your sound waves are going to hit first, that is generally a good place to put some absorption foam.  Also, right behind your speakers as they are going to project a lot of bass and unwanted energy out of the back of the speakers.  That may create a bass build up.

 

Final thoughts

Acoustic treatment won’t give you sound proofing.  So if you’re looking for a way to keep your under rehearsed, not ready for live performance band unheard or if you’re looking to keep those loud explosion rumbles and piercing horror screams within the confines of your home theatre, acoustic treatment panelling won’t do that for you.

However, if you want your room to sound the best it can by getting rid of rouge frequencies, high end flutter echo and boomy bass corners, acoustic foam treatment will get you there.  There is no one size fits all for treating your room, every room is different and its up to you how much you want to change the sound of your room.  For example, if you’re recording acoustic acts and want to have a bit of reverb/ambiance in your recording room you won’t want to deaden the sound too much.  If you’re building a vocal booth you might want to deaden the sound as much as you can, so you’d use more acoustic foam to get rid of any reflections of sound.

There is plenty of information and YouTube videos out there on this topic.  Do yourself a favour and research as much as you can.  The more you know, the better result you’ll get when acoustically treating your room.

 

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