How Acoustic Treatment Works – Improve the Sound of Your Room

🔑   Key Points
The key to a great sounding room is first understanding how reflected sound works and choosing a room and location within the room that minimises it, both from your guitar and your studio monitors (if recording and mixing your own music). Usually this means positioning yourself as far from your walls as possible when performing or mixing. Once this is addressed, acoustic treatment such as acoustic tiles, panels, and bass traps can be used to further improve the sound of the room. Identify the first reflection points in your room first (usually your side walls) and then focus on the corners of the room and ceiling directly above you.

Improving the Sound of Your Room

We acoustic guitarists are always chasing tone. This often leads to discussions on body shape and tone woods, strings, including gauges and materials, picks, microphones (if recording) and of course playing technique. But, one often overlooked aspect of a great sounding guitar that rarely gets mentioned is the environment itself e.g. the room you are practicing or recording in.

The sound of the acoustic guitar, being an acoustic instrument (who’d have thought?) is of course, very much influenced by its surroundings.

In some cases, this will be outside of your control, as anyone who has performed live in different venues can attest.

But when it comes to your room there’s actually a LOT that can be done to improve the sound you are hearing and this can make all the difference when it comes to feeling inspired to practice and/or record.

In the following article we’re going to discuss what causes poor room acoustics and why some rooms just tend to sound a lot better than others. We’ll also discuss how to pick the best room in your house to rehearse or record in, where you should position yourself within the room when playing and some options with regard to acoustic treatment e.g. bass traps, acoustic tiles, and sound panels.

Much of the information included below applies to home recording, but following the recommendations outlined below will help any room sound better, regardless of whether you are interested in improving the sound of the room you practice in, or if you are recording acoustic guitar and vocals.

So, if you have noticed your guitar always seems to sound better when you play it outside of your home studio, the information in the article will help you improve things dramatically.


Sound Proofing V Acoustic Treatment

Soundproofing V Sound Treatment

Before we go too far down the path, an important distinction should be made.

Sound treatment is not soundproofing.

It’s easy to see why this is confusing. If you type ‘soundproofing’ into a search engine like eBay you will be returned acoustic treatment products, like acoustic studio tiles.

Acoustic Treatment Products

Acoustic treatment involves improving the ‘acoustics’ e.g. the sound of your room. Soundproofing is used to prevent sound entering or escaping from the room, and is usually done to prevent noise complaints (from neighbors) or to prevent outside noise e.g. traffic noise from being picked up by a microphone.

They are fundamentally different problems and require different approaches.

In most cases a soundproof room is essentially an air-tight room. Acoustic tiles, while effective at reducing the energy of sound waves bouncing around your room (more on why this is important shortly) will have little effect on sound waves escaping the room or entering the room from outside.

It’s also important to keep in mind, a completely soundproof room may not even be a particularly good sounding room under most circumstances, particularly the inexpensive home studio and may end up sounding artificial and sterile.

Aren’t professional studios soundproof?
Sure, many of them are, but recording rooms in professional studios are often purpose built, rather than repurposed, so they are built soundproof. Effective soundproofing that doesn’t destroy the natural acoustics of a room such as this involves utilizing cavities between the walls of the room and utilizing products high in density such as rock wool and mass loaded vinyl. The internal surfaces of the walls are largely unaffected, making the professional studio essentially a room is a room within a room. This means some natural reflections still occur, giving the room a more realistic sound.

How acoustics work within a room

It’s useful, before diving into a solution to first understand the problem we’re trying to solve.

When it comes to practice spaces or home studios, most of us are limited when it comes to choice e.g. a home based studio often doubles as a bedroom or home office, and we don’t have a range of options to choose from.

Sure, a lot of us practice guitar sitting on the couch in front of the TV also, but the repetitive nature of practice can start to become a problem for the other residents of your home. Because of this, I’ve found it is always best to have a dedicated practice area or home studio. And, besides, if you do happen to find yourself practicing on the couch, tone probably isn’t the main priority as opposed to developing muscle memory.

So, what makes a great rehearsal room or home studio?

The truth is, most of us won’t have the luxury of choice and instead will take what we get. I know myself, my home office/studio is far from ideal acoustically, but it also happens to be the quietest room in my home when it comes to outside noise, and doubles nicely as a home office, so what ya gonna do?

In any case, if you do have options you should be aware that there’s far more to a great sounding room than using acoustic treatment products. All environments influence sound e.g. the size and shape of the room, height of the ceilings, materials used e.g. plaster or brick walls, ceiling and floor, along with what’s actually in the room e.g. furniture. Basically, everything about the room will have an impact on what you hear.

The term ‘acoustics‘ refers to the science of sound and this includes:

  • How sound travels from the source (e.g. the acoustic guitar) around a room
  • How the environment e.g. the characteristics of the room influences the sound (probably a much bigger factor than many realize)
  • How sound is first detected e.g. by the ear, a microphone or both, and then interpreted by the brain.

Acoustics is a branch of physics, referred to as acoustic engineering, and those who undertake an education in acoustics can earn a master’s degree. In short, it’s a complex subject , and this article really only covers the tip of a very large iceberg, but it’s a subject worthy of at least understanding the basics regardless of whether you are a performer or simply want the best sound from your home studio or theater, and especially if you record acoustic instruments and vocals.

How sound is influenced by it’s environment

Direct sound and reflective sound

To best describe how sound is influenced by an environment, let’s start with an example.

Say you are sitting in your practice room or home studio, acoustic guitar in hand. When you strum a chord, the sound waves generated don’t just travel in one direction (e.g. the initial direct sound you hear with your ears or is detected by a microphone).

Sound waves travel in multiple directions, and multiple angles of the same direction resulting in reflected sound from your ceiling and walls that much like a rubber ball bounces around your room.

So, depending on the room, what you hear isn’t just the direct sound but a combination of direct sound and reflected sound.

Direct and Reflected Sound

These sound reflections mean you or your microphone are hearing sound waves at different rates of decay, which quickly results in a loss of clarity.

Why does reflected sound reduce clarity?
When a direct sound is quickly followed up with reflected sound, our ears detect both the direct and reflected sound as a single source. If the secondary source is detected beyond a certain amount of time, approx. 50ms (this can vary) we hear this as natural reverb aka echo and interpret this as two separate sources of sound. However, a very short duration between direct and reflected sound waves makes what we hear appear as one sound and becomes less articulate or poorly defined, resulting in a loss of clarity. This becomes even more complex with regard to specific frequencies interacting with each other resulting in what is known as comb filtering.

Comb Filtering

When two audio signals blend together with a very small delay, as you might expect from a combination of reflected and direct sound within a room. Some of the frequencies of both the direct and reflected interact with each other. Some frequencies are ‘in phase’ e.g. the wave forms of the two combined signals are aligned, causing the signal to increase in amplitude aka volume.

Sound waves - Peaks and Troughs

Other frequencies however will be out of phase. If the peak of one signal however is aligned with the trough of another signal this can cause both frequencies to cancel each other out. This is relative to how much crossover of signal occurs, e.g. a slight overlap will result in a slight reduction in signal.

The reflected sound also interacts with the surfaces it is reflected from.

This works much like EQ, in that it may limit and also emphasize specific frequencies over others depending on the characteristics of the materials in your room.

This is similar to tone woods in the construction of a guitar e.g. denser harder timbers e.g. maple often results in a brighter sound, whereas Mahogany (a more absorptive material) often results in a warmer sound.

So what you ultimately end up with in a room with flat reflective surfaces is a mix of differently accentuated frequencies, you are not strictly in control of caused by sound waves bouncing around your room, hitting your ear or microphone at slightly different times. All in all, a recipe for a poor sounding, and unfocused room.

Remember when we discussed acoustic instruments being highly influenced by their surroundings, this is what I was talking about.

So what can be done to rectify this?


Room Selection

As they say, a goal without a plan is merely a wish. Therefore, to create a better sounding room we need a plan, and this begins with picking the right room.

Now, If you are anything like me, you probably don’t have the luxury of selecting from a range of available rooms in your home, but if you do have options consider the following:

  • Avoid small rooms
    Small rooms can be a problem, as you are essentially unable to escape close proximity to walls and sound reflections.
  • Avoid perfectly square rooms
    If the room is square, regardless of where you position yourself you will still be in close proximity to your walls, meaning there’s no sweet spot in the room.
  • Avoid low ceilings
    Low ceilings reflect sound just like walls and other reflective surfaces.
  • Avoid sparse rooms
    Sparse rooms with hard reflective surfaces throughout e.g. bare walls mean there is nothing on the wall to absorb sound. This is where soft furnishings e.g. curtains or a free-standing bookshelf can help absorb reflected sound and minimize its effects.
  • Avoid dead sounding rooms
    Likewise, the room should not be full of clutter and sound dead either. A room that is too absorptive will sound unnatural and lose clarity in the higher frequency ranges.

Don’t worry if your room doesn’t exactly fit the bill, as outlined above. Most home studios don’t…but through a combination of good positioning and correct use of acoustic treatment there’s a lot that can be done to improve things further.


Room Position

Once you have selected your room, consider where you will position yourself, and your desk including studio monitors and microphone if recording.

Avoid Corners

It may appear obvious, now that we have discussed reflected sound and the problems this causes, not to position yourself near your walls, and good for you, that’s correct.

However, if your home studio or rehearsal space is also an office or multi-purpose room you might already be playing in the corner of the room as this is the least disruptive option.

When I first moved my operation into my home office after my previous room was required by my wife when she began working from home (thanks babe!), my desk which was home to my computer was parked in the left corner of the room.

That may not seem a big problem, e.g. you can always plug your microphone into your interface and sit in the middle of the room or rehearse from the center of the room. But, when you also need quick access to your mouse and keyboard to control your DAW being too far from your desk can be a problem. However, there are solutions for this issue, both simple and complex which I’ll touch on shortly.

Another potential problem with being in a corner is the difference in reflections between your side walls. One wall is almost directly beside you, while the other is much farther away resulting in a mix of fast decaying and slow decaying sound.

Bass Reflections

Another issue with being too close to a corner is the build up of bass frequencies e.g. frequencies below approx. 300Hz. These are longer and more powerful than high end frequencies. Because of this they don’t bounce around your room as much as high frequencies and tend to build up in the corners of your room.

As a result small rooms, such as your basic home studio or rehearsal space often suffer from uneven bass response and/or distortion of bass frequencies.

While this can be addressed, at least in part with acoustic treatment (more on this shortly) you are much better served getting away from the corners of your room completely to limit the build up of bass frequencies and cost of materials to nullify them.

The ideal placement

The first thing you should do is consider how you will be using the room. For example, if you have a modest home studio and plan, as both the performer and engineer to position yourself near the back of the room to limit reflected sound, your studio monitors may then be directly facing a wall.

Ideal Room Placement

This is actually quite a big deal with regard to recording, as what you hear when you are mixing obviously plays a large role in the actions you take with regard to levels and EQ. If your studio monitors are within close proximity to your walls they won’t give an accurate representation of the performance and may sound completely different when played outside of the room e.g. on a living room stereo or your car.

With this in mind, you will need to consider things from both a performer’s and the engineers’ perspective.

What you are really aiming for is a balance between practicality and getting away from your walls for both performing and listening.

In practical terms this really means when performing position yourself closer to the center of your room, away from any walls or corners. You should also consider moving your desk close to the back of the room with your monitors facing toward you, and away from the rear wall (as per the example below).

The location of your speakers and your seated position should form a triangular shape.

Also ensure your desk is not hard up against your wall as this can result in mechanical vibrations. If possible pull the entire desk out about 18 inches.

This obviously creates a bit of an issue if recording as it can be difficult if performing to be more than an arms reach away to control your DAW and maintain good mic position. There’s a few different ways you can address this.


Controlling your DAW away from your computer

Remote Control App

Many DAWS now include an integrated phone app, which serves as a remote control allowing you to control your DAW from the position of the performer e.g. away from the desk. I’ve included links to the more common ones below:

Ableton: https://help.ableton.com/hc/en-us/articles/209071989-Apps-for-controlling-Live-with-an-iOS-or-Android-device

Cubase: https://new.steinberg.net/cubase-ic-pro/

Reaper (another hugely popular DAW) includes a feature for controlling it through a web browser, meaning you can control it using the browser on your phone.

Use a Wireless Mouse

Personally, I just use my wireless mouse most of the time. I place a bench or stool beside me and simply control Logic Pro from there. This obviously won’t be an ideal solution in a particularly large room, or if you have trouble seeing the screen comfortably but for smaller rooms this is more than sufficient.

Use Pre-roll

Most DAW’s utilize a pre-roll function which essentially allows you to hear a nominated amount of time before it begins editing/recording. Pre-roll is useful regardless as part of the recording process but can also allow you sufficient time to hit record and get yourself in position to record.


Acoustic Treatment

So once you have covered the basics of room selection and considered where you will be performing within the confines of your room, the next logical step is to look at acoustic treatment e.g. using acoustic treatment products such as sound panels, bass traps and diffusion to improve the sound of the room.

It’s important you don’t just start at this step. It’s much better to understand how sound reflections occur and how this impacts the sound of your guitar. It’s also important to address these with regard to room selection and placement before considering acoustic treatment, as they will invariably make a bigger difference than acoustic treatment.

So what is acoustic treatment and what is it designed to do specifically? Before we go too far let’s discuss what acoustic treatment products are designed to do and what they are not designed to do.

Acoustic treatment reduces reflected sound.

We’re not really trying to remove all reflected sound completely, that’s not the intended goal. Completely eliminating reflected sound within a room leaves a room sounding dead and lifeless, as explained in the earlier section on sound proofing.

Using Acoustic Treatment as EQ

What we’re trying to do by using acoustic treatment is enhance the sound of the room e.g. make it sound great, not dead.

This means the room should have some natural reverb, but not so much that it muddies up the sound. It also shouldn’t have an abundance of low and high frequencies which tend to make a room sound unnatural.

In this capacity, acoustic treatment can be compared to EQ. By using it we can reduce specific frequencies that can overwhelm the ears or microphone e.g. low frequencies that build up around the corners of the room and high frequencies that are fairly common in rooms that aren’t purpose built for recording or performing.

High frequencies are often even more of a problem than low frequencies.

Remember when we discussed low frequencies being more powerful and longer than mid and high-range frequencies? High frequencies as you may have guessed are less powerful and shorter, and as a result they can accumulate quickly within a room, having a big impact on the sound heard.

That’s not to say bass frequencies aren’t a problem, they are and also need to be addressed.

Types of acoustic treatment

Acoustic TilesAbsorption

Absorption products e.g acoustic tiles, acoustic panels, and bass traps are the most common forms of acoustic treatment available, especially in the home studio or rehearsal space. They are relatively inexpensive, simple to install and do a great job.

They are used, as the name implies, to absorb sound, ultimately reducing reflected sound within the room.

Most absorptive products are constructed from foam, however many are also made from fiberglass due to its density, being much greater than acoustic foam.

Acoustic tiles, panels, and bass traps come in different sizes and thicknesses. As discussed, lower frequencies are longer and stronger, so it stands to reason the thicker the foam or fiberglass absorption used the more successfully it will reduce bass frequencies.

Bass TrapsBass Traps

Bass traps are a type of absorptive acoustic treatment but with a primary focus on absorbing low end frequencies.

You many have guessed, they are primarily used in the corners of a room where bass frequencies tend to build up and as a result come in a wedge shape, so they can easily be installed in the corners of your room.

Addressing a build up of bass frequencies is important, especially when it comes to mixing your music if recording. Excessive bass will force you as an engineer to make mixing and instrument level decisions that might suit the room your are currently in but will result in a less than ideal mix outside of the room.

Diffusion

DiffusionIf you have ever been to a theater or concert hall you may have noticed the ceiling and wondered why it looked the way it did?

Those intricate designs are not merely aesthetic. They are actually used to reflect and diffuse sound.

But aren’t we trying to reduce reflected sound?

While that’s the intended goal of acoustic tiles, diffusion is used to spread sound out evenly maintaining the balance of the room. It doesn’t reduce reflected sound as acoustic tiles do, instead retaining any natural reverb the room might have while dispersing the sound evenly throughout the room.

They are less common than absorptive products and used far less often in the home studio or rehearsal room environment because ideally they are best suited to a room that already sounds great, like what you might expect if going to the theater.


Floors and Ceiling

So far we’ve only discussed the walls of your room, but what about the floor or ceiling?

Floors can be tricky. Take a look at the floor of your room, it will be either carpet, wood, or tiles, unless using a rug on a timber or tiled floor.

Carpet is absorptive, while tiled or timber floors are hard and reflective resulting in a lot of reflected sound.

Your ceiling will almost certainly be reflective, as ceilings are usually long flat expanses, broken up only by a few fixtures such as lighting and ceiling fans.

Therefore, the floor is important because any sound reflected from the ceiling will come into contact with the floor and reflect even further unless absorbed.

If you have a reflective floor, you may want to consider reducing those reflections coming from the ceiling by using acoustic tiles on the ceiling, in most cases directly above your head and using a carpet or rug on the floor.


Where to buy acoustic treatment

You can pick up decent acoustic treatment products online using either eBay or Amazon or a dedicated acoustic treatment supplier. Room kits are also available that include both bass traps and acoustic tiles, along with the necessary adhesives to allow you to apply the products to your walls and ceilings. I’ve included links to some of these below.

How much you need, really depends on the size of the room and the amount of treatment required. With this in mind, it makes sense to first identify your first reflection points and other problem areas in your room before ordering, which we will do in the next section.

Fixing acoustic products to your walls

Before installing your acoustic products, decide whether you want to use an adhesive (this can be problematic with regard to plaster walls) or double-sided tape. Use enough of either to ensure a stable install that won’t come off the wall at a later date and use a spirit level (if you have one handy) to ensure your panels are hung straight. Nothing ruins the aesthetics of a home studio like poorly installed acoustic treatment, and a great looking, well treated room can be a source of inspiration for home based musicians.

What acoustic treatment to use and where to put it

Ok, so we now know what products are available, what products are we going to need and what do we then do with it?

First Reflection Points

In most home studios absorptive products such as bass traps and acoustic tiles will be of the most use. Diffusion, as mentioned, is mostly used to stabilize a good sounding room already, hence why you mostly see diffusion employed in theaters and concert halls.

Installing acoustic treatment begins with identifying the first reflection points of your room. This is important, because if you can identify the place where sound is being reflected initially this will cut down on a lot of the reflected sound completely, as it is less likely to bounce around the room.

The most common first reflection points are your side walls, treating these effectively will arguably create the biggest difference when it comes to cleaning up the sound of your room.

We can use a simple trick to identify where these first reflection points are on the side walls by using a mirror and ideally a second person to assist.

The Mirror Trick

I’ve written about the mirror trick before, and there’s a lot of information available online about how it is done, but in simple terms we are going to be using a mirror to see visible reflections on our side walls.

Why use a mirror?

Sound waves move around a room in a similar way to light. By utilizing a mirror at approximately ear height we can establish where the sound waves first hit the side walls by using the mirror to identify an object behind us.

Confused?

The video below explains things in more detail and the steps below it outline exactly how it is done. Note, that will the video applies to studio monitor placement, the same methods can be applied to your microphone. Try to identify the reflection points for both by marking the all in the areas the mirror identifies.

  • Also, keep in mind if referencing your studio monitors, the angle the monitors are on is important. Ensure your monitors are facing inward on a slight angle, directly at your ears if seated at your desk before using the mirror trick and maintain this position in the future to get the maximum benefits of the applied sound treatment.

Using Bass Traps

Bass traps are purpose built for corners. They are wedge shaped and fit within the angle of two adjacent walls perfectly.

Ideally, you will cover all four corners of your room in their entirety, from ground to ceiling. However, if resources are more limited than this cover the front two corners e.g. the direction you will face when playing guitar and cover at least head height, by matching the height of your previously installed acoustic tiles on your side walls.

Treating the ceiling

After treating the first reflection points on your side walls and balancing the bass response of your room using bass traps, the next most important area to treat is the ceiling, specifically the area directly above when you will be seated.

At a minimum cover the area directly above you, while also trying to align with the first reflection points on the walls on either side of you. In many cases they will be very close.

Treating your front and rear facing walls

The next thing you are going to want to do, provided you have sufficient acoustic panels is to treat your rear wall to minimize slap back reflections.

What is a slap back reflection?

A reflection with more associated delay compared to the first reflection points on your side walls. They often occur at the point the furthest away from the original source of sound within the room and have more of a noticeable delay between the direct and reflected sound.

It may seem counter-intuitive, but your front and rear walls are much less important than your side walls, ceiling and corners with regard to acoustic treatment. In fact, if you can only afford a few acoustic tiles or panels, treat the side walls and perhaps consider the ceiling, followed by your remaining walls at a later date.

If you are treating your front and rear walls, there’s no mirror trick when it comes to ideal placement, so for the most part we’ll be taking an educated guess at the best location.

Cover the rear wall first followed by the front wall (the wall you will be facing if seated at your desk or in the middle of the room when performing) if you have sufficient acoustic tiles.

For the rear wall I like to match the width of my desk (on the front facing wall) at head height.

For the front wall, I recommend installing acoustic panels at the same height directly opposite the front wall. Depending on how many acoustic tiles you have at your disposal many people choose to simply cover the area directly behind their speakers.


What next?

If you have some left over acoustic tiles, start filling in some of the largest gaps. This may also depend on other components in the room e.g. book shelves, or furniture, but in general look for wider expanses of wall and apply some treatment to these in a balanced fashion.


Summing things up

That was a lot to take in. I hope the information above helps you improve the sound of your room, whether you are operating a home studio and recording and mixing music or simply want your guitar and perhaps vocals to sound great in the room you prefer to practice in.

Regardless of your intended purpose, always keep in mind the acoustic guitar is an acoustic instrument and will be greatly influenced by its surroundings. Anything we can do to improve how the sound waves emanating from the guitar interact with the environment it is being played in will only benefit the performance or recording being undertaken. This is especially the case for the humble home studio, so consider improving the sound of your room first before investing in new speakers, plugins and other equipment, after all when it comes to making great sounding music what we hear is really all that matters.

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