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What is sound and why do we need acoustic treatment?
What problems do most people run into when using acoustic treatment?
Learn one simple trick to improve your room acoustics without spending more money.
Proper acoustic treatment is essential for any environment where critical listening is desired. Home theaters, recording studios, music rooms, and even general living spaces can benefit from acoustic treatment albeit to different extents.
Unfortunately, treatment is commonly misunderstood and therefore, misused due to its complexity and a lack of clear guidelines.
For example, I have seen plenty of beginner audio engineers cover every wall of their creative space with foam mattress toppers to emulate what is seen in professional recording spaces.
Treating a room in this way is fortunately unnecessary and can result in worse sound quality. This begs the question− does acoustic foam actually work?
In order to properly answer this question, we must first understand the physical properties of sound.
What Is Sound?
Sound is simply our perception of vibrations in the air.
When a guitarist plucks a string, the back-and-forth movement of the string creates micro-vibrations in air that spread out just like ripples in a pond. We are graced with the sound of music when those back-and-forth ripples reach our ears.
Sound becomes very complex in rooms because it bounces and reflects off walls, floors, ceilings, and any other surface (including you).
There are also strong resonances that form in all rooms based on their length, width, and height. These reflections and resonances create the sound of your room.
As an example, consider how your voice sounds in a washroom versus your bedroom.
It is important to understand that these room colorations can be beneficial or very detrimental to our work as audio engineers. In the case of home studios, a single bedroom often functions as both a mixing and a recording environment. Therefore, less than stellar room colorations will likely negatively affect the following:
Instrument choice, tuning, and preparation
Digital signal processing within a digital audio workstation
Absorption And Acoustic Foam
So, what can we do about bad room colorations? Cue acoustic treatment. Acoustic treatment, such as foam, is a great way to fight undesirable room colorations and restore accuracy to our listening space. Here are some examples of acoustic treatments and methods of effecting a rooms’ sound.
Reconstruction of room size or walls
Placement of equipment within the room
Placement of listeners within the room
Acoustic foam, i.e. absorption, is a very popular method of acoustic treatment because it is both readily available and relatively inexpensive. This is great news!
Acoustic foam works by reducing the amount of sound energy within a room. The sound energy does not disappear, rather, it is converted into other forms of energy. Recall that sound is micro-vibrations within air. As those vibrations pass through foam, the material membranes vibrate as well. The result of these vibrations is friction and heat. Viola… sound energy is dissipated as heat.
With this understanding of acoustic foam, it should be clear that any porous or cloth-like material absorbs sound. This means that blankets, couches, pillows, window curtains, laundry, and the clothes you are wearing right now function as sound absorbers. So to finally answer the question, yes acoustic foam does work.
Consider The Type Of Acoustic Foam
Professional acoustics companies, such as Auralex and GIK Acoustics, use specific materials for their absorptive properties. This means that there is a difference between the membrane cell structure of mattress foam and that used for acoustic treatment. Further, many professional companies will only use materials that stand the test of time and hold-up to building fire codes. It is important to consider whether your treatment is acoustic foam or just foam.
Another key factor with absorption is the thickness of each panel. As a rule of thumb, thin pieces of acoustic treatment target higher frequencies. Much thicker material is needed to efficiently absorb lower frequencies. Therefore, using only thin acoustic foam will disproportionately absorb high frequencies without providing benefit in lower frequency regions. The result is an unnatural sounding room that is no longer musical. This leads us to our one simple trick to improve your acoustic treatment without spending more money.
Prepare Your Mounting
Let’s assume you already have some acoustic foam on hand. Most people tend to mount their foam directly on the wall. This significantly limits its efficiency as thinner absorbers mainly address higher frequencies (this is a result of particle velocity and sound boundary interactions with surfaces).
Thicker foam, however, is more efficient at absorbing a broader range of frequencies. Therefore, mounting your thin acoustic foam even a few inches off the wall can drastically improve its benefits. The effect is twofold in that:
You will improve the lower frequency ranges affected by your treatment
You will further improve how well it absorbs high frequencies.
Acoustic Foam Placement & Positioning Tips
Treat The First Reflection Points
Start by treating the first reflection points on the horizontal axis. If you are not sure where this is, sit in your listening position and imagine where sound from your speakers hits your side walls and bounces back to you. It is very important to place acoustic treatment here as it will improve your stereo width and clarify your imaging.
Pay Attention To The Weak Areas
You should consider placing some acoustic treatment between the speakers and your front wall. Applying acoustic treatment here helps reduce reflections emanating from the back of your speaker. This is a tricky area as boundary interactions can cause a significant dip in your low-mid frequencies; however, for most home studios it is likely best to place your speakers as close to the wall as recommended by the manufacturer. If there is any space left between the wall and your speakers, place acoustic foam there.
Don’t Forget The Corners
If possible, mount some of your acoustic foam across corners of your room. This can be done between two horizontal walls or even the ceiling and side-wall. This will inherently create a large air gap behind the foam. This can be your start to absorbing those low-frequency resonances mentioned above. As your studio grows, you will need to add larger and thicker absorbers in your corners to further treat bass resonances.
Build An Acoustic Cloud
This next recommendation is easiest if you have a drop-down hanging ceiling. Your goal is to create an acoustic “cloud” that hangs a few inches from your ceiling over your listening position or musical instruments. This is like the first recommendation in that you are applying acoustic treatment to the first reflection point above you.
Acoustic treatment can also be placed directly behind you on the back wall of your room. It can also be extremely helpful to place a couch at this location−recall that any soft porous material will absorb sound.
Making these small adjustments to your acoustic treatment can help reduce the pitfalls discussed above. Furthermore, you may not need as much acoustic foam as you have improved the efficiency of what you already have. This is really a win-win situation.
Don’t Overdo It
Acoustic foam can be a fantastic first step in improving a rooms’ acoustics; however, if used in excess it can make a room sound lifeless, unbalanced, and unnatural. There is a very common trap that I myself fell prey to when first starting out. Firstly, people acquire cheap packing or bedding foam and arbitrarily apply it to their walls.
Right away there is an audible difference, and it is assumed that an improvement has been made. It is then taken to the extreme, whereby nearly all surfaces are covered with foam. Unfortunately, this is all too common and it does not result in the best sounding room for music recording or production.
Warning signs that you may have “too much” acoustic treatment:
Your room has an uncomfortable feel.
The musical quality seems lifeless and unnatural.
Your recordings always sound boomy and or muddy.
Acoustic Foam Recommendations
While it may be tempting to purchase off-brand items due to cost, you are not doing yourself any favors. Many of these products are not tested and therefore have poor performance. Furthermore, I have personally seen some of these cheaper alternatives begin deteriorating over time.
There are numerous large and start-up acoustic treatment companies. Therefore, I highly recommend you do your own research and see what fits your needs. Many of these groups, fortunately, offer acoustic consultations at no cost. Here is a shortlist of some excellent manufacturers.
It can easily cost thousands of dollars to properly treat a room. This is largely due to lower frequency resonances which tend to require more advanced and tuned forms of treatment. However, that is not to say that a room’s sound cannot be drastically improved with even minimal treatment applied properly. Hopefully, these tips will get you in the right frame of mind that you do not need to spend ridiculous amounts of money to get the job done.
Keep in mind that acoustically treating a room tends to be a fluid process. Room acoustics is complicated so give yourself credit for starting that journey.
Remember — there are plenty of musicians and producers releasing professional work in very modest home studios – Billie Eilish comes to mind. Don’t be dissuaded by the glimmer of commercial setups.
Begin experimenting with what sounds best in your space and always remember to stay positive, push your musical boundaries, and have fun!