The Main Types of Acoustic Treatment and How to Use Them
Don’t know an absorber from a diffusor from a hole in the wall? Read on for a primer on the main types of acoustic treatment and their effects on your room.
Many large and well-established studios throughout history have become renowned for the sounds they have been able to achieve. While the engineers, the equipment, and even luck, all play a role, there is one other factor that is almost always present.
One of the main reasons for the unique sound of successful recording and mixing rooms is that the space’s strengths and weaknesses have been assessed and managed using a combination of acoustic treatments.
As home recording continues to thrive and smaller studios become increasingly common, what do those building or upgrading their studios today need to do to make sure they are getting the most out of their environment?
Why does acoustic treatment matter?
In most cases, the aim of a recording session is to capture the performance as accurately as possible. Unwelcome acoustic effects can make getting an ideal-sounding take into a major challenge. Similarly, a mix engineer is put on his or her back foot from the start if the audio requires additional work to compensate for acoustic issues and ambient noise.
Put simply, every surface in the live room will affect the movement of sound waves. Depending on the size and shape of the room, and the materials used in its construction, most untreated spaces will be plagued by unwanted reverberation, flutter echo, inadequate frequency response, standing waves and modal problems.
With effective acoustic treatment, the quality of your recordings and mixes will not only be enhanced, but you can even control and manage the acoustic signature of your room for different types of performance.
This is why acoustic treatment for the studio is so vital. Installing acoustic foam for instance, softens the surface area, increasing the level of sound absorption and minimizing the reverberations hard surfaces create, resulting in a better quality of sound. But it’s not the only type of treatment, and may not even be the best for every application. Read on below as we cover each of the main types of treatment and evaluate their strengths and weaknesses.
Soundproofing and acoustic treatment: What is the difference?
Initially it might be easy to confuse soundproofing and acoustic treatment. Both are important, and play very different roles in a studio’s design.
When soundproofing a room, the intention is to isolate the room from outside sound. Often, the dense materials required will be installed during the construction of the walls to prevent sound from leaking in or out. But the goal here is acoustic isolation, rather than controlling the color of the sound within the room.
While the budget for effectively soundproofing a space may not be available to smaller studios, some knowledge and modest spend on acoustic treatment can significantly boost the quality of the results in a studio.
While acoustic treatment may not help isolate your space from the outside environment, it can help you manipulate the acoustics of a space to minimize echo and low end inconsistencies, and improve the sound quality overall.
In general, you are much more likely to notice an improvement in the quality of your finished tracks if they are recorded in an optimized space, rather than on professional equipment used in a poorly treated room.
Types and placement
Bass traps are a type of acoustic treatment that are often placed in the corners of the studio to deal with issues around lower frequencies. Two kinds of bass traps used in studios, porous absorbers and resonant absorbers.
Porous absorbers are usually made of foam or rigid fiberglass and will need to be spaced away from the wall to most effectively absorb bass frequencies. These types of absorbers commonly work as broadband absorbers, soaking up high and mid frequencies as well as low frequencies.
Resonant absorbers can be placed closer to walls and can be better for dealing with specific bass frequencies, use a tuned vibrating panel to reduce their effect. Unlike broadband bass traps, they will want to be tuned to an appropriate room mode by an acoustician to get the best possible results.
Acoustic panels are like porous bass traps, but are less thick, and therefore, less effective at low frequencies. They might be placed directly against walls to help mitigate flutter echo.
Ceiling clouds are lightweight acoustic panels designed to be suspended horizontally from the ceiling in order to minimize natural reverberations of live rooms and control rooms, especially those with high ceilings.
Diffuser and deflector panels are similar in their end result, but use a different technique. Rather than absorbing the sound, these panels scatter sound waves in random directions to reduce echo.
Helmholtz resonators are narrowband treatments constructed from a tube or container. The size is determined by the frequency that needs to be absorbed, typically 100Hz and lower. The container vibrates at its resonant frequency, removing it from the space. This type of treatment is ideal for resolving a specific frequency issue, but is not as effective for general use.
Rigid fiberglass insulation is ideal for broadband bass traps, as the density can be varied, allowing for versatile placement and broadband treatment. Despite the name, rigid fibreglass is very easy to shape and work with.
Thicker panels can absorb longer wavelengths and are required for capturing the lowest bass levels, but implementing a wall gap when fitting panels will allow thinner panels to absorb more bass. One general rule for the best results is to allow a gap as wide as the panel is thick. Coupling this with corner positioning can help these traps be effective at even lower frequencies.
Acoustic foam is typically created from polyurethane and is designed to reduce airborne sound waves by increasing the air resistance, then converting the dispersed energy into heat. Depending on the requirements of a specific room, the foam is often cut into pyramids or wedge-shaped tiles and placed strategically on the walls and ceiling in order to optimize sound absorption and control reverberation.
The Sabine formula is a useful way to determine how much acoustic treatment is required and where it needs to be placed. Wallace Clement Sabine, an American physicist known as the “father of architectural acoustics” developed a formula to determine the optimal reverberation time for sound-based performances in a range of venues. For a medium-sized auditorium, that is between 1.5 and 2.5 seconds to ensure clarity and rich sound. While this is ideal for live music, playback through speakers for mixing would require levels closer to half a second.
The most important thing about capturing a good recording is that the equipment should be secondary to the recording space’s acoustic treatment. After all, even the finest kit can only capture what is in the room, and even the best mix engineer can’t make decisions without a trustworthy monitoring environment.
One of the biggest benefits of acoustic treatment compared to new gear is that it can be relatively inexpensive to implement and, in some cases, can even be a DIY project, allowing you to greatly improve the result of your recording and mix sessions at a surprisingly low cost.
Please note: When you buy products through links on this page, we may earn an affiliate commission.