The science of acoustics focuses on how sound waves behave in an environment. Because sound comes in the form of waves, it is recommended you check out the article entitled “How Sound Waves Work”. After reading that article, you will be able to have a better grasp and therefore image in your mind of how acoustics are studied. In short, sound waves are rated and categorized by their intensity (frequency), phase (time), and amplitude. Each of these characteristics distinguish each sound from the next. We use the measure of these characteristics, coupled with the knowledge of our surroundings to measure how one affects another.
In the context of recording studio, acoustics comes into play in several aspects such as construction, recording or tracking, mixing, and mastering. If you are unfamiliar with any of the terms we are using here, feel free to read our other articles about them or request articles about the subject you’d like to read about. Because acoustics can make or break an album recording it is necessary to take into consideration the science as an audio engineer. If you have ever been in an acoustically correct room, you have noticed several visual, and audible differences than the everyday living room. For example Bell Labs has one of the largest and most state of the art acoustically correct rooms in the world. In this photo you can see the amount of acoustic treatment that is on the walls as well as the false floor. While this is an anechoic chamber, and not a recording studio, they both strive to achieve sonic isolation. This room is eerily quiet and as stated does not allow echos to be born from signal generation.
In fact more importantly the sheer geometry of the room construction can be more effective in sound isolation and the acoustic solution. Generally live rooms, or where the actual recording of the sound takes place in a studio, are built asymmetrically with varying materials on all opposite facing walls. Ideally it has been said that a dome or igloo is the ideal shape for a recording room, however this shape can produce equally strange effects if not built correctly. The floor of a properly treated live room is raised above the foundation in order to create an air lock, or dead space that is used to isolate the room from low level ground vibration. This technique of raising the floor above the foundation is known as “floating” the floor. A great studio will extend this technique to the walls and also use proper insulation materials to further prevent any leakage of sound. Any windows separating the control room from the live room as well any other intermediary ports that can pose as access points for sonic leakage.
For example windows that are acoustically treated are built with double pained, angled glass or plexiglass so that there is an air-lock separating each of the panes. This extra volume of air will pad or cushion any extra disturbance produced by the sound. The walls, for example, are ideally angled at opposite supplementary angles to each other with opposite live/dead materials for interior facing walls. A basic example is the chessboard pattern, every opposing and adjacent wall should have staggered material and angle pitch. However, one particular construction style among studios is not mandatory to all studios. Some professional studios are equipped with variable walls and ceilings to change the qualities of the room. Another great example of acoustic treatment is the application of sound diffusers, which are textured surfaces that scatter or diffuse sound in order to eliminate certain phenomena to be described. The picture below is of a skyline diffuser, made usually of wood featuring pseudo randomly generated heights calculated by specific mathematical algorithms tailored to a specific frequency range.
All of the mathematical precision and engineering expertise that is used to design and develop our recording studios goes without much recognition to engineers. However, this engineering is integral and necessary to our work. We use these resources to control and deal with physical phenomena such as resonance, early reflection, standing waves, and combing. You can read more about these phenomena by requesting articles here or by taking the time to research various audio engineering, physics, and acoustics forums and books on the web and in libraries. Briefly, resonance is the doubling in amplitude of a wave which to us as audio engineers make the particular frequencies louder and cut others, in turn degrading our true sounds. Early reflections occur when the source sound, and sound reflected off of a surface reach the listener subject, whether human or microphone causing comb filtering which similarly cuts out some desired frequencies and further degrades the sound as well. Just to put some perspective on the sensitivity of the human ear I should tell you that when wearing a baseball cap, the brim notches out frequencies around 2 kHz?! If you experiment, you will notice the difference. This is why everything down to the construction of our mixing consoles, and the desks they sit on are critical in proper tracking, mixing, mastering. Ever wonder why most mixing consoles and desks are at that increasing angle? Well all of this is the required thought necessary to avoid the previously mentioned phenomena from giving us undesirable and unusable recordings.