SOUND PROOFING
& ACOUSTIC TREATMENT
Soundproofing and acoustic treatment are important topics to tackle when setting up a studio/jam-room. Even if all of your sounds are electronic, the room you are in will strongly affect the sound you are hearing through your monitors.
SOUND ISOLATION
Keeping noise out (and in). Traffic noises, dogs barking, lawn mowers and the TV are all things you don't want recorded onto your tracks. You need a way of keeping those noises out of your studio - particularly when you're using microphones. If you live near an industrial area or highway, you may find that vibrations also affect your recordings. Thirdly, if you have live instruments—or just like to play loudly through your monitors—you also need to think of your family and neighbors. You want your music to stay in the room.
NOISE ELIMINATION
Equipment noise from within the room can also spoil a recording. Consider keeping your power amps and computer boxes (which fans that might be noisy) in another room. Also look for other potential sources of annoying noise.
ACOUSTIC TREATMENT
The way different frequencies are absorbed or reflected by your walls and other hard surfaces can negatively impact on the reverb and EQ that are picked up by your mics, and that you hear when listening to your monitors.
SEPARATION
If you are recording more than one instrument at a time—or singing while playing an acoustic guitar—then ideally you will want each separate instrument on its own track without too much bleed through from the other instruments. This isn't a major concern of most home studios (where instruments tend to be recorded one at a time)
STEPS TO EFFECTIVE ACOUSTIC TREATMENT
STEP 1 - SETUP YOUR ROOM
Every room is unique and everything in the space will affect its sound. Wall angles, flooring, windows, doors and of course its overall shape will all dramatically change the way sound is perceived within the room. The first thing to do in any situation is to identify the problem areas in your room and home in on the issues that need to be addressed.
Extremely large rooms often have many inherent problems, such as standing waves, nodes and large amounts of reflection. These problems often require a lot of treatment to rectify. The sheers size of the walls in larger rooms will mean that more acoustic treatment is required.
Very small rooms will arguably present fewer problems from the offset but there will be obstacles nonetheless. Lower frequencies will often not have space to develop in these more confined spaces and this can lead to mixes that don't translate well to larger systems. Unfortunately a lot of the problems caused by monitoring in smaller rooms cannot be solved using acoustic treatment, so the only remedy here might be to relocate!
As far as shape goes, there are a huge number of variables here but as a rule symmetrical opposing surfaces are not ideal and rooms with differing angled walls will be much easier to treat.
STEP 2 - LISTENING POSITION
First up the sound coming from your monitors needs space to develop, especially the lower frequencies. Try not to position your workstation in an alcove or too close to any walls. The same goes for your listening position, this should be a good distance away from any walls as well. Some speakers for example will be rear ported and these need to be placed at least ten inches or so away from any hard surface in order for the bass be reproduced correctly. The same goes for any subwoofers that are rear or side ported.
Another important thing to think about here is something known as the 'sweet spot'. This is really just the ideal position between your speakers. With your speakers positioned correctly you should be able to draw a triangle between your ears and each speaker. The speakers should be positioned so they face down the lines of this triangle and if they are above you in height they should also be tilted downwards.
If you are positioned correctly in your room and you are in the sweet spot you should get a good stereo image and be able to hear all the frequencies your system is producing. You should now be ready to identify and tackle any acoustic problems the room may be throwing at you.
STEP 3 - ABSORPTION
This is possibly the most commonly used acoustic treatment in home studios, in fact it is possible that it is over used. In some studios this will be the only sort of treatment you'll see and often far too much of it. This can have a really negative effect on your final mixes.
Absorption is needed where there is a lot of reflection taking place.
This will present itself as an echo or ring in your room and will usually effect the mid and high frequencies. These echoes are called early reflections and if untreated can be very fatiguing to the listener over time. It's also hard to get an accurate high end mix when these are present.
Absorption treatment most commonly comes in the form of tiles, and these can be of various densities and textures. These tiles will actually absorb a proportion of the sound that hits them. This means less reflection and less of the signal coming back to the listener.
The trick is here to do things a little at a time. As a general guideline you are looking for about 70% coverage using some kind of acoustic treatment.
STEP 4 - DIFFUSION
Some reflection of the sound in our workspace is actually a good thing, believe it or not. Hearing some of the mix come back to our ears from various parts of the room can help create a realistic stereo image and a more open natural sound.
The problem is that if you simply leave areas of wall bare to create this reflection you will get a horrible slap back style delay and this is far from desirable. Other hard flat surfaces such as your computer screens and work surface can also create this sort of unwanted reflection.
The answer to this problem is diffusion. This is similar to reflection but instead of all the sound being reflected in one go it is diffused and returned to your ears at many different intervals.
When you see a diffuser you will immediately see how they do this. An average diffuser panel is made up of numerous small segments. These may appear random but are designed using exact mathematics. The Skyline range of diffusers for example uses a primitive root formula, meaning each section is an exact prime number.
This sort of treatment works really well in smaller rooms and can greatly enhance the stereo image and overall sound of a room when applied correctly.
STEP 5 - BASS TRAPS
Fine tuning your space to reproduce low frequencies correctly is an art of its own and can prove to be a challenge. The first step here is to use traditional bass traps to treat all the corners of your room. This will help to prevent the powerful omni-directional low frequency energy from grouping and creating bass heavy spots. If you need to you can also treat the join between the ceiling and walls.
If after this initial treatment you are still experiencing bass heavy areas in your room, it is likely that you have nodes or standing waves occurring. These can be reduced using heavier wall mounted traps. These are similar to broadband absorption panels but are usually made up of several layers and of much denser material. These are pretty expensive to buy but if you are confident enough DIY versions can be effective.
STEP 6 - DECOUPLING & ISOLATION
When treating your room it is worth looking into isolating your speakers and subs. By using dense platforms under your speakers you can 'decouple' them from your workstation, desk or floor. This will do a few things, firstly it will prevent anything the speakers are resting on from resonating.
This means you will be listening to your mix and not the furniture in your studio. Secondly decoupling will reduce the amount of low frequency transmitted into the walls, floor and ceiling of your studio, cutting down on the sound traveling into adjoining rooms.
Subs can be isolated using dense pads especially built for the job and you can also decouple kit that is effected by vibration. For example turntables can be isolated to prevent errors in playback in loud environments.
STEP 7 - PLACEMENT
When it comes to actually sticking the panels, traps and diffusers up you have a few choices. For a permanent solution go for glue. For a more semi permanent, re-fixable option try spray adhesive and if you need something that leaves absolutely no marks at all you can get velcro pads or pins to hold the treatment in place.
Diffusion panels can be placed above any hard surfaces such as a workstation or computer monitors, and absorption panels can be alternated with diffusers for a more open sound in the room. This can be adjusted to taste as you go.
Treating the room for bass frequencies should be a separate process really and this is one area you can afford to be pretty heavy handed in. It's pretty difficult to go over the top here but treating all corners is a pretty safe bet.
Apply a good mix of treatment types, add more treatment a bit at a time and take time for critical listening sessions throughout the process.