A Guide To Acoustic Treatment For Home Recording

The short answer: Acoustic treatment involves modifying the characteristics of a room to enhance clarity, by reducing reflected sound. This means positioning yourself as far from your reflective surfaces (such as walls) as possible when performing and using acoustic treatment products such as acoustic tiles, panels, and bass traps to absorb reflected sound waves.

For a complete guide continue reading.

Improving the Sound of Your Room

The acoustic guitar, being an acoustic instrument, is influenced by its surroundings.

This will sometimes 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 a LOT that can be done to improve the sound quality.

In the following article, we’re going to discuss:

The primary cause of poor room acoustics.
How to pick the best room in your house to record in
Where you should position yourself within the room when performing
How to apply acoustic treatment e.g. bass traps, acoustic tiles, and sound panels.

Sound Proofing V Acoustic Treatment

Before we get too far, an important distinction should be made.

Sound treatment is not soundproofing.

It’s easy to see why this can be confusing, as both terms are often incorrectly used interchangeably. For example, if you type ‘soundproofing’ into eBay you will be shown acoustic treatment products, like acoustic studio tiles.

But there is a big difference between the two. Acoustic treatment involves improving the ‘acoustics’ e.g. the sound of your room. Soundproofing is used to prevent sound from entering or escaping from the room and is usually done to prevent noise complaints or to prevent outside 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, that a completely soundproof room 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 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 within a room.

How acoustics work within a room

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 (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, it’s a complex subject. But, it’s a subject worthy of at least understanding the basics especially if you record acoustic instruments and vocals.

Direct sound and reflective sound

As an example, let’s 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.

Depending on the room, what you hear isn’t just the direct sound but a combination of direct sound and reflected sound (See diagram below).

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 a 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 a natural reverb (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, 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 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 waveforms of the two combined signals are aligned, causing the signal to increase in amplitude aka volume.

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 tonewoods 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 within a room with flat reflective surfaces is a mix of differently accentuated frequencies hitting your ear or microphone at slightly different times. All in all, a recipe for a poor-sounding 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

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 unable to escape 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 close 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
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 acquired by my wife when she began working from home (thanks darlin!), 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 centre of the room.

But, when you also need quick access to your mouse and keyboard to control your DAW this quickly becomes tedious. 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 sidewalls. One wall is almost directly beside you, while the other is much farther away resulting in a mix of fast decaying and slow decaying soundwaves.

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. Bass frequencies 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 an 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 to get away from the corners of your room completely to limit the build-up of bass frequencies and the 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.

This is quite a big deal with regard to recording, as what you hear when you are mixing plays a large role in the actions you take concerning levels and EQ. If your studio monitors are within 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’ perspectives.

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

In practical terms, this means when performing you should position yourself closer to the centre 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 creates a bit of an issue if recording as it can be difficult if performing to be more than an arm’s reach away to control your DAW and maintain a good mic position. There are a few different ways you can address this.

Controlling your DAW away from your computer

Remote Control App

Some 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

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

Use Pre-roll

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

Acoustic Treatment

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 products such as sound panels, bass traps, and diffusion to improve the sound of the room.

This should never be the first thing you do however. 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 trying to remove all reflected sounds completely, that’s not the intended goal. Eliminating reflected sound within a room leaves a room sounding lifeless, as explained earlier.

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 reduces clarity.

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.

Types of acoustic treatment

Absorption

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’re used to absorb sound, ultimately reducing reflected sound within the room.

Most absorptive products are constructed from foam, however many are also made from fibreglass 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 Traps

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

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 you are currently in but will result in a less-than-ideal mix outside of the room.

Diffusion

If you have ever been to a theatre 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 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 the sound out evenly. It doesn’t reduce reflected sound as acoustic tiles do, instead of 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 theatre.

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 timber or tiled floor.

The carpet is absorptive, while tiled or timber floors are hard and reflective resulting in 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.

How much you need, depends on the size of the room and the amount of treatment required. With this in mind, it makes sense to 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 them?

First Reflection Points

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 sidewalls, 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 sidewalls.

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 while the video applies to studio monitor placement, the same methods can be applied to accommodate your microphone. Try to identify the reflection points for both by marking 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. As mentioned, they are wedge-shaped and fit within the angle of two adjacent walls.

Ideally, you will cover all four corners of your room, from ground to ceiling. However, if resources are limited, 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 sidewalls.

Treating the ceiling

After treating the first reflection points on your sidewalls 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 a more associated delay compared to the first reflection points on your sidewalls. They often occur at the point the furthest away from the 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 sidewalls, ceiling, and corners with regard to acoustic treatment. If you can only afford a few acoustic tiles or panels, treat the sidewalls 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 making 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 leftover acoustic tiles, start filling in some of the largest gaps. This may also depend on other components in the room e.g. bookshelves, or furniture, but in general look for wider expanses of walls and apply some treatment to these in a balanced fashion.

Summing things up

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 vocals to sound great.

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 what matters most.