What Is The Ideal Ceiling Height For A Recording Studio?
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You may have visited some professional recording studios and noticed that the rooms had high ceilings, especially the tracking room. Now in your home studio do you need a high ceiling? In this article I will talk about why higher ceilings are beneficial and some of the room acoustic theory behind recording studio room design.
1) High Ceilings Are Great For Drum Recording
A very basic, but important reason large pro studios have high ceilings in the tracking room is to give the wave forms enough space to develop before hitting a surface and reflecting back to the microphones and your ears. This is especially true when recording drums or large ensembles like an orchestra.
In most home studios an 8 foot ceiling barely gives you enough height to place the overhead mics. You will mostly pick up the cymbals in a lower studio and the reflections from the ceiling will create a "harsh" tone. This is a very practical reason for having larger ceilings, but what about the physics of room acoustics? How do room acoustics improve with higher ceilings?
2) Room Modes
To really grasp why higher ceilings are beneficial in a room, we must first understand some basic room acoustic physics. All rooms create reflections where sound waves bounce off of. When sound emanates from a source, say a speaker, the air in the room is excited by the sound waves. The sound travels in all directions from the speaker and bounces of the walls, ceiling and floor. When the sound bounces off the surfaces it then returns back into the room. The reflected waves then encounter new sound waves coming from the speaker and they interact with each other. The sound waves either create a boost because of constructive interference or they create a null known as destructive interference.
These peaks and nulls in the sound waves create acoustic distortions. Now, there is a slight difference in how higher frequency sounds behave versus lower frequency sounds. Sound waves above 250Hz perform more like a "ray." Meaning they travel in a direct line and don't have as much energy as sound waves below 250Hz.
Sound waves below 250Hz and especially below 100Hz have much more energy and have much longer wavelengths. These sound waves create what we call room modes. These room modes or are areas of high or low pressure due to those sound waves running into themselves after bouncing off your rooms surfaces.
Okay, that was a bit complicated, but it is very important to understanding why high ceilings are important. The reason is that we ultimately want larger rooms to allow for enough space for those low frequency waves to fully form or at least form as much as they can before hitting a surface. Depending on the distance the waves travel from a source (speaker) and a surface (ceiling) the room modes will change.
3) Room Ratios
This brings us to the next point about ceiling height. The ceiling is only one part of the room. We must also consider the length and width of our room when designing a recording studio. Over the years some acousticians have come up with room ratios that create a pleasing acoustic environment for sound reproduction.
These room ratios should be considered a starting point and are by no means the end all be all of acoustic design. You may be wondering as I did why we don't know the way to design the perfect room for a recording studio. After all, if we can measure room modes and use room ratios to reduce them why not build the perfect mathematically correct studio?
The answer is that, acoustics is as much an art as it is a science. Just because one room sounds good to one person does not mean it will sound good to another. In fact, the way we perceive sound is uniquely human. We do not hear everything the way the math works out in physics. We hear how our ears and brain perceive sound in a room. This makes the job of designing your studio that much less precise, but also gives you the freedom to design a room that is pleasing and does the job you need it to.
All this said, we can use room ratios to get us in the ballpark with a room that will have less acoustic problems and thus cost less to acoustically treat in the long run.
Some common room ratios are from the acousticians, Sepmeyer, Louden, Volkman and Boner. Below is a diagram of some of their room ratios.
4) The Problem With Small Rooms
Now you can use these ratios, but you are not guaranteed great results if your room is still small. The reason is that if your rooms dimensions are comparable to the wavelengths of audible sound then may have problems with "excessive separation between modes." (Everest,Pohlmann 261) The large separation between modes leads to unpleasant acoustic distortion in your room.
To get uniform spacing between room modes and avoid coincidences (where modes pile up on top of eachother) you need more room volume. This means larger rooms are generally thought of as sounding better and are preferred for tracking rooms and control rooms. However, in control rooms the reverb time must be lower and all reflections must be treated to create a flat listening response.
It is very important to remember that "there is no ideal ratio of dimensions" for a room. (Everest,Pohlmann 256). As studio designers we can only create a good starting point and then measure and analyze the room once it is built.
For most of you reading this, I would assume you are working with rooms you already have or may be able to build a studio in your backyard. Either way it is important to remember that the larger the volume the better your room will sound and if you use room ratios you will have a better starting point.
In a basement studio this could mean building a wall in the existing basement to create an ideal room ratio. In a studio build in a backyard it could mean building a larger studio to help with even distribution of room modes and avoiding coincidences.
To answer our original question. The ideal ceiling height is probably the tallest ceiling you can afford while making sure it fits within a good room ratio for the least acoustic distortions caused by room modes. In the end don't lose sleep over this, but know that understanding room modes is an important aspect of getting your room to sound as good as it can from the start.
Everest, Frederick A., and Ken C. Pohlmann. “Modal Resonances.” Master Handbook of Acoustics, McGraw-Hill, New York, 2015.