Do you need to think about treating your home recording studio with acoustic panels, bass traps and other acoustic treatment solutions? If you are a complete beginner then you should focus on purchasing the right mic and interface so that you can get started quickly making good quality recordings on your computer.
Once you have got through that initial expense and learning curve, and you want to start refining your recordings, then it may be time to start thinking about how echoes, reverb and leakage are affecting your recordings, and to consider whether you need to do something about it.
In this post we take a good look at how sound behaves in rooms and how this might affect your recordings. You may find you get a better recording result with some simple acoustic treatment of your studio- either DIY or by purchasing bass traps and acoustic foam panels.
Quick Acoustic Solutions
By using close miking techniques, direct recording of guitar and by overdubbing you may be able to make good recordings in a room without any acoustic treatment. If you do find your recordings are muddy or boomy, then you could try the following:
Bass Traps. These are probably the single most important element of acoustic treatments, and the first thing you should try if you are unhappy with the acoustic quality of your recordings. In small home studio rooms where bass frequencies can be a particular problem, bass traps are often an essential. But as they are good at absorbing mid/high frequencies as well, sometimes these alone can be enough to get the job done and improve your recordings to your satisfaction.
Acoustic Panels. These are available very cheaply, and although they are not so good at absorbing excess bass frequencies, they do help to kill any standing waves that may exist between opposite parallel walls (another real problem in small studios). Placing these behind your monitors and on the wall where the main reflection points occur will make a difference and won’t cost much to implement. They are also much less obtrusive.
The Behaviour of Sound In Rooms And How To Manage It
First a bit of background on what is happening to sound waves in your studio.
Musical instruments make sound waves that travel outward in all directions. Some travels directly to your ears or to a microphone and that is called direct sound. The rest of the sound strikes the walls ceiling floor and furniture in your recording room. Some of the sound is absorbed, some is transmitted through the surface and the rest is reflected back into the room.
Soundwaves take time to travel and so you will hear the reflected sound after the direct sound. The reflection repeats the original sound after a short delay. If the delay is more than about 50 ms we call it an echo. In some concert halls you can hear single echoes. In smaller rooms you often hear a short rapid succession of echoes. These are called flutter echoes.
You can hear them yourself by clapping your hands next to a wall. Flutter echoes occur when sound bounces back and forth between two parallel walls.
Sound reflects many times from all the services in a room. These reflections extend the sound of notes as the musician plays. This persistence of sound after the original sound has stopped is called reverb (reverberation). For example, reverb is the sound you hear if you shout in an empty gym. Your shout stays in the room and gradually dies away or decays.
Reverb is hundreds of echoes gradually getting quieter. These echoes follow each other so rapidly they merge into a continuous sound. Eventually the surfaces in the room absorb the echoes. The timing of the echoes is random, and the echoes increasing number as they decay.
Reverb is a continuous fadeout of sound while in echo is a discreet repetition of the sound.
Echo = “HELLO ..hello …hello”
If the reverb time is too long when you are recording it can make your recorded sound seem distant, muddy and washed out.
As a rule of thumb, Pop music recordings are often made in a dead or non-reverberant studio and then effects are applied afterwards. Classical music is often recorded live because the reverb with classical music is part of the sound.
Reverb comes from every direction because it is a pattern of lots of reflections off the walls ceiling and floor. Because your brain can tell where sounds are coming from you can distinguish between a direct sound of an instrument coming from a single location and the reverb coming from everywhere else. You are capable of ignoring the reverb and concentrating on the sound source. In fact normally you are not even aware of reverb is small recording room.
Try this experiment. If you were to put a microphone next to your ears, record an instrument, and play back the recording you will hear a lot more reverb on the recording than when you heard live. Why is that?
The reverb you record is not all around you. Instead it’s all up front between the speakers. You can hear it more, you can’t discriminate against the reverb spatially.
To reduce the amount of reverb you capture in your recordings, you need to place your mics close to instruments and possibly try using sound absorbing materials to your room.
When sound waves strike and reflect off bumpy or convex surfaces they spread out or diffuse. This diffusion can be used to weaken sound reflections.
Diffusion panels may be a handy addition to your studio – although usually in a small room use of bass traps and acoustic panels is usually enough. (In my study I have a wall of bookshelves which makes a handy diffusion panel!)
Sound from an instrument travels to the nearest mic, but can also ‘leak’ into mics intended for other instruments. This overlap is called leakage. It’s important to try and reduce leakage to a minimum and ensure each mic only picks up its intended instrument. Another reason to close mic.
The other cause of leakage is when a vocalist is singing along to a track playing back in headphones and the sound from the headphones is picked up by the mic. See our article on studio headphones to help you choose headphones that minimise this problem.
How To Tame Echoes and Reverb With Acoustic Panels and Bass Traps
Echoes and reverb can make your recordings sound very mushy and distant. There are two ways you can try and prevent these problems: with recording techniques; and with acoustic treatment.
Let’s look first at what you can do without purchasing or making any further equipment, and just thinking about where and how your are recording.
Controlling Recording Room Problems With Recording Techniques
Sometimes you can make clean recordings in an ordinary room if you follow one or more of these suggestions:
- Mike close. Place your Mike 1 to 6 inches from your instrument or voice. Then your Mike will hear more of your instrument and less of the room reflections. You might want to use mini mics which attach directly to your instrument. Do beware, though of proximity effect which can sound boomy or bass heavy. – Some mics have a bass-rolloff switch, or experiment with the angle of the mic.
- Use directional mics which reject room acoustics especially from behind the mic (look for cardioid, super cardioid, or hyper cardioid pickup patterns)
- Record your bass guitar and synth directly with a guitar cable or direct box. Because you omit the microphone you pick up no room acoustics. To get a good sound when recording electric guitar try direct recording off the effects boxes, or use a guitar amp simulator, rather than recording the sound of the amp with a mic. That way you avoid the issue of room reverb and echoes and the need to do anything about it.
- Record instruments one at a time rather than recording them all at once. You will pick up a much cleaner sound. The problem will be that you lose some of the emotional connection that occurs when when musicians play together but it will help to get a cleaner recording and will certainly reduce the problem of leakage. As a compromise, you could try recording all the loud instruments at once: drums, bass, and electric guitar. Then you could overdub the quieter instruments: acoustic guitar, sax, piano, vocals.
- If you can, record in a large room – especially if you are recording a group. This lets you spread the musicians further apart and weakens the sound reflections from the walls into the mics.
- Another option is to purchase a small portable vocal booth, or use portable free-standing acoustic panels (sometimes referred to as gobos). The benefit is you could take these with you if you record elsewhere, and it avoids doing anything major or semi-permanent with your recording studio room.
Controlling Recording Room Problems With Acoustic Treatment
If any of the following occur in your recording room you might have to consider trying different acoustic treatments to improve your recordings.
- If you clap your hands next to a wall and you hear flutter echoes these are caused by sound bouncing back and forth between hard parallel walls
- Your studio is a very live environment such a garage or a concrete block basement and you hear too much room reverb
- Your studio is very small
- you can hear outside noises in your recordings
- Your bass guitar amps and monitor speakers sound boomy
- You want to be able to place the microphone further away from your instrument without picking up noise or excess room reverb
- You can hear a lot of leakage in the mic signals
If any of the above apply to yourthen here are a few suggestions on how you could upgrade the acoustics in your studio.
Please note that acoustic treatment is not the same as soundproofing. The following tips will help you reduce reverb, echoes and leakage on your recordings but will not help with acutal soundproofing.
Reverb and echoes are caused by sound reflections so any surface that is highly sound absorbent helps reduce these problems.
The DIY approach
To absorb high frequencies, use porous materials such as bumpy foam mattresses or panels. Check the foam you are using is flame retardant or treated. You can nail or glue foam to the walls or mount in frames.
Leave some space between the foam panels. This helps to spread out the sound. But don’t overdo foam padding. A stuffed dead room is uncomfortable to play in. Keep some reflections because they add air and liveliness to your sound.
Other high-frequency absorbers are sleeping bags, blankets, carpets, curtains and fiberglass insulation cupboard with muslin.
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- versatile – use free-standing in their self-contained frames or pin to studio walls
- effective – ability to shift them around easily means you can experiment and find the perfect position
- particularly useful to kill standing waves and flutter echoes
- attractive – frames give them a smart look
The alternative to the DIY approach is to purchase specially designed acoustic damping sound absorbing panels such as the Soundwave Squares. The Soundwave Squares comprise a waved surface of polyester fibre with effective sound absorption attributes. They are a neat option because they come ready mounted in their own frames and can be fixed on your wall very easily with simple thumb tacks due to their very light weight. You can choose whether you hang them with the waves running vertically or horizontally (or alternate between the two). The other benefit of these squares is you can use them freestanding and so experiment with their placement around your microphone while you are recording, or behind your monitors while you are listening and mixing.
Acoustic Foam: many companies make a range of acoustic foam panels in various sizes at different price points. Brands to look out for are Auralex and Ultimate Acoustics.
Acoustic panels have become so cost effective that it is barely worth making your own when they are so readily and cheaply available, and will be aesthetically more pleasing as well.
It is also possible to buy acoustic foam or other sound absorbing surfaces by the roll if you have a larger space you wish to treat. This will be a more cost-effective option for bigger rooms.
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Bass Traps – DIY and Commercial
To absorb low frequencies you can either purchase or make bass traps. Here arefour different suggestions to make your own:
- Resonant tube trap: take a 35 to 55 gallon rubber trashcan and fill it with fibreglass insulation (make sure you wear a dust mask and gloves). Cover the open end with muslin or canvas.
- Frictional tube trap: make a 2 foot diameter canvas bag 8 feet tall and fill with fibreglass insulation. Hang one back a few feet out from each room corner. Experiment with how far into the room you hang these.
- Lattice: build a 3 foot wide flat lattice frame of wooden slats the same height as the ceiling. Cover the frame with muslin. Put the frame diagonally across the room corner and fill the corner with R-30 insulation. Put one of these in each corner.
- Insulation panel: get eight pieces of 2 foot x four foot X four inch rigid fibreglass insulation type 705 from an insulation supplier. Cover each piece with Muslim to contain the fibres. Place piece across each room corner with the narrower edge touching the floor. Stack two panels to make them 8 feet high.
There are other ways to absorb bass sounds. Wood panelling can work well. It also helps if you close cupboard doors and place settees and books a few inches from the walls. In my own studio I happen to have a wall of books which seems to really help with diffusing the sound, and they are on suspended shelves so sit a couple of inches from the wall.
You may not need any bass traps if you don’t put any bass into the room. For example, if you just record the bass guitar direct and have the bass player wear headphones to monitor himself as he plays.
Again, though, the price of commercial bass traps has dropped to the point where you may find it is pricier to take the DIY approach than simply buy the right kit! Foam bass traps are easy to find on Amazon and eBay and these are probably easier to handle and more effective. Plus again they are going to look better! But some people prefer the old skool approach of making do what they have to hand.
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Another problem you may encounter is the issue of standing waves. If you play an amplified bass through a speaker in a room you may hear some notes that boom out in the room as you work up a scale. The room is resonating at certain frequencies. These resonance frequencies occur in patterns called standing waves. They can give a very boomy colouration to musical instruments and monitor speakers.
This problem is worse in a cubical room full. Standing waves are a lot less problematical in rooms where the length width and height are not multiples of each other. Try to record in a large room if you can because the room resonance frequencies are more likely to be below the musical range and so you won’t experience the problem in the same way.
Or, use your trusty bass traps to absorb room resonances.
Soundproofing and Making A Quieter Studio
It can be very difficult and expensive to completely soundproof a room especially if you are using a room in your house for multiple purposes, but the following hints and tips may help to keep noise out, or down to an acceptable level.
- Turn off appliances and telephones before you start recording
- Pause for ambulances and aeroplanes to pass
- If it is an option consider having the studio in a basement because the earth blocks noises from the outside
- Remove small objects that rattle and buzz
- Close windows, and consider covering them with plywood if that’s a possibility
- Close doors and seal with towels
- Weatherstrip doors all round including underneath, remember to leave the doors open for ventilation when not recording
- Replace hollow doors with solid doors
- Put several layers of plywood and carpet on the floor above the studio and put insulation in the air space between the studio ceiling and the floor above
- Place mics close to instruments and use directional microphones. This will not reduce noise in the studio but will reduce noise picked up by the microphones (you will note that this is the solution to many of these problems)
Your home studio may not need acoustic treatment. Make test recordings to find out. But if you think your room could stand some improvement then hopefully some of the above suggestions will help point you in the right direction.
For the best results and a more professional appearance consider buying acoustic room treatment equipment. It used to be a very expensive luxury but is now very affordable.
However if your budget is really tight and you are just starting out, begin with your microphone and audio interface as your first purchases and experiment with a DIY approach. Get the clothes horse and mattresses out!
Over To You
Let me know in the comments about your experiences with acoustic treatment, or post a question if you can’t find your answers here. I love to hear what you think.