Soundwaves travel and strike walls in predictable ways. However, how the sound reflects once they hit the wall or a hard surface is different. Controlling how reflected sound moves is the key to making your home studio sound good. There is no 100 percent perfect sounding room, but educating yourself and making key decisions about your recording space can significantly improve it.
Acoustic treatment involves applying solutions that will help absorb or diffuse sound to improve how your recording studio will sound. The three key areas of a home studio acoustic treatment are low-frequency control, control of early reflections, and control of sound decay.
Common Acoustical Problems
Regardless of the space you set up your home recording studio, you will face some common acoustic problems. These include comb filtering, room modes, flutter echo, and excessive decay time.
Comb Filtering
This is when the sound produced is combined with its reflection within a short interval. Comb filtering sounds like a jet plane landing. Some common situations you’ll encounter comb filtering include;
- Using two mics at different distances from the same source
- Having a hard surface near a microphone
- A hard surface reflecting the speaker’s sound
- Two speakers projecting sound into the same space
To eliminate comb filtering, pay attention when combining signals, be careful when using multiple mics on a single source, and deal with reflections of your speakers on walls and other hard surfaces.
Room Modes
These are naturally occurring resonances, also called standing waves. They are caused when sound travels or reflects off various surfaces like two side-by-side walls or between the floor and ceiling. Adding acoustical treatments like bass traps and acoustic panels can reduce the effects of room modes, standing waves, nodes, and anti-nodes.
Flutter Echo
This usually occurs when two parallel surfaces reflect sound between one another, causing a series of echoes. Flutter echoes differ from long-delayed echoes or reverberations because they are multiple echoes that occur in rapid succession. To deal with flutter echo, acoustic panels can absorb or diffuse the flutter echo.
Excessive Decay Time
When you’re in a gym or cathedral, echoes can be heard for several seconds after the source of the sound stops. This is the decay time when a sound wave bounces around without being absorbed or diffused. Long decay times will make it harder to mix cleanly in the room. Acoustic panels are great at diffusing and absorbing long decays.
Solutions to Acoustical Problems
Low-Frequency Control
Bass traps or low-frequency control devices are the most important considerations during acoustic treatment. When the low frequencies are poorly controlled, your mixes might sound muddy (too much bass) or Thin (less bass). The recordings could also have bad resonance or cancellation effects (hollowness). Controlling the low frequencies can smoothen things out.
Bass Traps and acoustic Panels in a Home Recording Studio
The effective frequency range of loudspeakers or other sound sources should be considered when choosing the best acoustic treatment for low frequencies. Most good low-frequency devices can address a wide range of low-frequency problems. However, they tend to be expensive or take up too much space. Pressure, velocity, and hybrid devices are used for a home recording studio. However, there are a lot of DIY approaches that are also effective.
- Pressure Devices – These are placed directly in the room corners or the wall and ceiling of the room. The corners of a room are always high-pressure areas, and these devices control pressure buildup. Pressure control devices include resonating devices, such as solid panel absorbers, Helmholtz devices, such as perforated panels, and slat absorbers.
- Velocity Devices – These can be as simple as thick, porous materials placed on the wall with airspace. The thicker the material and deeper the air space, the better control you’ll have of the low frequencies. An excellent example of a velocity absorber is a thick piece of mineral fiber (4″-thick) with around 3pcf density over equal-sized airspace.
- Hybrid Devices – These work as both pressure and velocity absorbers. They are the most commonly used in recording studios to control low frequencies. Dense foam absorbers are a good example, and they can control most frequencies depending on the size. Dense fiber panels placed over the corners can also be used as low-frequency hybrid absorbers.
Early Reflection Control
Controlling early reflections is done mainly using absorption materials. Because the frequency range of reflections is higher, even thinner materials can be effective. This offers you more choices when it comes to aesthetics and home recording finishes. In most recording studios, the common materials used are one of the three “Fs” fiber, fabric, or foam.
- Fiber – These are usually 3-8pcf fibers and other natural (cotton, wood) and synthetic (polyester) fiberboards. If mineral fiber panels are used, you can cover them with an acoustically transparent cloth to improve the aesthetics of the studio.
- Fabric – Curtains are the most commonly used fabric in home recording studios. Heavy drapes or blankets are more effective in multiple layers and should be at least 3 inches thick for better results. However, compared to fiber and foam, the use of fabric could be more effective.
- Foam – Foam is the studio’s most used product for reflection control. 1.5 to 2.5pcf acoustic foam panels are usually used. Foam comes in different shapes and designs for aesthetic purposes. The minimum overall thickness of the foam absorber should be 2 inches.
For all the above products, the thicker the material, the better it will perform. For higher frequency reflections, the thickness should be 4-6 inches. If you want to absorb more low frequencies, a thickness of 12 inches would be suitable.
Locations to Add Acoustic Treatment
When your studio monitor speakers produce sound, there are three stages in which you’ll perceive it:
- Direct sound, which is clean straight from the speakers.
- Early reflections are reflections off hard surfaces in a room, such as walls, floors, and desks.
- Lastly, You’ll hear a reverberant sound reflecting the original sound interacting heavily within the room.
The goal of acoustic treatments is to make the direct sound the main focus and reduce reflections and reverberant sounds to a high degree. Below are some locations where acoustic treatments are much more effective.
- Room Corners – The corners of a room are always the areas of high pressure where bass builds up. Bass traps are placed in the corners to control and absorb the bass build-up. For better results, do not place bass traps directly in the corner. Move them a few inches forward to enhance their absorption abilities.
- Sidewalls – Parallel sidewalls can cause a flutter echo. Installing acoustic absorbers, such as foam or diffusers, will help prevent flutter echo from occurring.
- Back Walls – The front and back walls are also parallel, which can result in flutter echo again. Room modes and standing waves can also be a concern. Thick hybrid acoustic treatments can help minimize standing waves and also help absorb the energy of low frequencies.
Apart from corners, sidewalks, and back walls, adding diffusers to large rooms’ ceilings and upper walls will prevent excessive decay. The use of reflection filters around the mic will also help keep your vocal recordings clean by absorbing unwanted noise around the mic.
