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Part Three - The Recording Room -- by Doug Fearn

Part Three - The Recording Room -- by Doug Fearn


The Recording Room -- Part Three

Written by Doug Fearn of D.W. Fearn -- Excellence in recording both in the studio and creating tube products for the professional audio engineer.

Recording takes place in an enclosed space, which could be a bedroom, a classroom, a recording studio, a concert hall, or a cathedral. (Recording can be done outdoors under ideal conditions, and it has a unique sound, but it is not often practical to do so.)
The space where music is performed has a large impact on how it sounds. A poor room may makes us feel uncomfortable about the recording. This can be entirely unconscious.
So what makes a good space for recording? Well, the size of the space is very important. We get auditory cues about the size of the room, based on the time it takes for the sound to be followed by a reflection or echo. Humans are very good at this, which can be unfortunate because bad-sounding rooms annoy us.
The reverberation time of a room is the time it takes for the echoes of the initial sound to decay to inaudibility. (The actual determination is more scientific than that, but this will do for our purposes.) A small room might have a reverberation time measured in milliseconds (thousandths of a second), while a large cathedral can echo for many seconds. Neither extreme is good for most music.
Most of the great recording studios in the world have a reverberation time of one to two seconds. A concert hall might be several times that long. Classical composers create music that is meant to be heard in a concert hall, and the conductor, musicians, and recording engineer take this into account and can use the reverberation to add excitement and drama.
Chamber music was meant for a smaller space. Folk-style acoustic music sounds best in a smaller room with little reverberation. Less reverberant rooms may contribute to the intimacy of very personal music. The music should drive the choice of the recording environment. Many recording studios have to accommodate a wide range of musical styles, and that requires skilled engineers to make it work. Some studios have methods to adjusting the acoustics to a limited extent.
In this discussion, a small room would be a typical household room. A medium room could be forty feet or more in most dimensions. A concert hall is much larger than that.
The reverberation time is affected not only by the size of the room, but also by the surfaces in the room. A room made out of stone (e.g. a cathedral) is going to have much more reverberation than one with drapery all around. An inappropriate reverberation time can ruin the music, so the natural characteristics of the room are important.
Many recordings utilize artificial reverberation to provide the illusion of the proper space for the music. This artificial reverb can conflict with the natural reverberation time of the room and degrade the sound, so many recording studios are purposely designed to have a short decay. Or perhaps there is no discernible reverberation at all -- the room is considered "dead." This is one solution, because a dead room can be modified with artificial reverb to make it sound like any sized space you want. That makes the engineer's job easier, but is it the best solution? I would say no, but there are many hit records made in very dead rooms, so it is not impossible. Dead rooms are not comfortable for musicians to play in either.

Another requirement for a recording studio is isolation from the outside world. There is a lot of misunderstanding, even among some audio professionals, about how to stop outside sound from intruding into the studio. Absorptive materials, like household thermal insulation, or drapery, do very little to stop sound intrusion. The only thing that works is mass -- big, heavy walls that are tightly sealed. Even a tiny gap in an otherwise solid and massive wall can seriously degrade the sound isolation, so great care must be taken in the design and construction of a soundproof studio. Any doors or windows need to be specially designed to stop noise transmission. Heating and air conditioning ducts need to be properly designed and constructed to reduce noise and prevent sound transmission. Needless to say, a proper recording studio requires very expensive construction techniques. No one wants to hear trucks passing by, people talking, or airplanes flying overhead on their recording.
With the advent of low-cost, high-quality recording equipment in the 1990s, it became possible to outfit a studio at much lower cost than it took in the past, when a single tape machine could cost as much as a house. This has opened up recording to anyone with a few thousand dollars to spend, and experienced people have made great records in their living room, bedroom, or basement. But the laws of physics still apply to a home recording studio, and eliminating outside noise (or bothering the neighbors), and designing the space to have a good "sound" can be challenging.
Not only does the recording space affect the sound of the recording, but it can also affect the performance itself. Musicians may unconsciously tailor their playing style to fit the room in which they are performing.
Small recording spaces eliminate the natural reverberation time of a large room and require artificial reverb (or none at all, which can also be effective). And recording at home allows a performer to re-record a performance if a dog barks or a truck goes by, an option that would not be tolerable in a professional studio. And, as we will see in a future installment, many of the problems of a small, acoustically uninteresting space can be mediated by the recording technique: single instrument or voice performances, layered one on top of another to achieve the final product.
Next we will look at some of the other characteristics of the recording space and their effect on the sound.