When recording it’s good to have a nice sounding room. In fact, this is one of the main things that makes a recording studio or an auditorium vital to the whole listening experience. A great deal of experimentation and a whole lot of money gets put into acoustic design and treatment. Beginning with the architecture; a room size, height and overall shape can play a tremendous role in how the sound will be heard.
Room treatments are a great way to control the acoustics and there are basically four types:
Absorption panels absorb most of the higher frequencies which are the commonly offending frequencies that travel the fastest and require the least amount of volume to make their journey around the room. These panels are usually placed behind monitor speakers to avoid bounce back from the walls. They’re also put on walls adjacent to the microphone to reduce nearby reflections. And they also help when put along the perpendicular walls of a mixing room so the engineer will hear the true sound coming from the speakers and not the interfering waves reflecting off of those walls.
Traps offer another solution by allowing a sound to continue its journey but funneling the direction into its largest section which absorbs the energy. These are great at reducing bass and can help prevent bass stacking. When bass frequencies are being folded on themselves from bouncing from wall to wall, they collide in different ways throughout the room and become unpredictable and hard to control. When the lower notes happen to reinforce each other by adding energy to the original signal, then the sound can be amplified and sound much louder than it actually should. Reversely, they can also collide at the same time in other positions within the same room in such a way as to subtract from the original signal and end up reducing the volume. The louder the speakers get turned up, the more likely there is to be stacking in the room. Traps work well in corners because this is where bass frequencies tend to collect before being thrown once again out into the room. The size of the room cannot be ignored; it is an enormous factor when it comes to hearing bass correctly. The smaller the room, the worse it will be.
Sound barriers are an impassible material or layer of materials which can be placed within the walls of a structure or wrapped along its perimeter and which will prevent sound from bleeding into the listening or recording environment. This type is usually placed during construction and many are made of multiple layers with one center layer being only air or even a gas of some kind, such as is seen with specific types of glass that are engineered for sound prevention. Isolation pads are another example of sound barriers and they are often placed under speakers or other loud sources to minimize the transfer of vibration to connecting surfaces.
Finally, in the case of listening environments like a mixing or mastering room, there may be some deflection panels placed in strategic locations to bring back some of the natural room reflection which is lost from the other types of sound treatment. A room with lots of absorption can sound quite dead and unnatural causing the engineer to overcompensate in his or her choices while mixing. Deflection panels are made up of many small reflective surfaces but which are all pointing in different angles of direction. This reflective array, if you will, helps distribute the reflections in a diffuse manner and helps to minimize the comb filtering that typical flat surfaces can create.
NOTE: IN A HOME STUDIO, WHERE ECONOMICS IS AN ISSUE, IT CAN HELP TO PLACE BLANKETS OR CURTAINS AROUND THE ROOM FOR ABSORPTION. AND WHEN MIXING IN SMALLER ROOMS, PLACING THE SPEAKERS ON STANDS, AT OR NEAR HEAD HEIGHT, AND POINTING AT AN ANGLE INSTEAD OF BACK AGAINST THE WALL CAN HELP MINIMIZE PROBLEMS.