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GRAPHIC DESIGN & ART ARCHIVE
Vocal Acoustics in Recording Studios and Concert Halls
Musical Acoustics - Professor F. Richard Moore - December 2009
Voice is an acoustically dynamic sound that depends on factors such as venue, audience, and construction. Singing especially, similar to most music, is a technique in which the performer aims for the listener to hear specific notes, tones, and modulations. In this paper, I will mainly focus on singing, rather than the spoken voice alone. I will then study how the acoustics of the singing voice varies through the acoustics of recording studio performances and the acoustics of concert hall performances.
Singing acoustics will be the foundation of this paper. Singing, like any noise, fundamentally begins with sound waves, alternately compression and rarefaction, that occur in the air (Vennard 2). It originates from air flowing through the lungs that then creates vibrations in the vocal folds of the larynx. It can be modified by the vocal tract, which is the space between the larynx, lips and nostrils (Howard and Angus 196). The internal sound originating from the performer can also be affected by the articulators, also known as the jaw, tongue, and lips. In singing, tones are interrupted by noises. Tones are referred to as vowels, and noises are referred to as consonants (Vennard 2). The vocal folds control the pitch of the sound, whereas the vocal tract determines the vowel sounds through its formants, and articulates the consonants (Rossing, Moore, Wheeler 373).
Spoken voice and singing differ in a few ways. According to The Science of Sound, there are four differences between spoken and sung vowels. One of these differences is the singer’s formant around 2500-3000 Hz (Rossing et. al 393). Specifically in solo singing, which will be the concentration of this paper, the energy is focused in the 2-4 kHz range, where the greater portion of the total sound energy is in the higher harmonics (Rossing, Moore, Wheeler 393). I will also assume a trained singer for the purposes of this paper, and assume the heavy mechanism (chest voice) and light mechanism (head voice) is utilized, in which the vocal muscles are active and passive, respectively, and air flow rate and pressure increase with the sound level.
Taking the acoustics of the singing voice into account, I can now discuss how these basics apply to how the singing voice is perceived through the acoustics of a recording studio. Sound isolation is one of the most important components of constructing a good recording studio. According to Philip Newell in Recording Studio Design, the three elements to sound isolation is rigidity, mass and distance (Newell 6). In this sense, lightweight buildings rarely provide good sound isolation for studios. There is great importance in eliminating outside noise from the inside of the studio. Once that is accomplished by creating a thick, rigid, heavy building distanced from outside noise, there are inside noises to eliminate as well.
Disregarding miscellaneous noise within the recording studio, the main issue of eliminating internal noise comes from the concept of reverberation. Reverberation is waves of compression that originate from the source of the sound and disseminate through the air in all directions (Lowery 71). In addition, the reverberation period is the time taken for the sound to stop lingering when the source of that sound stops making vibrations (70). The reverberation period is primarily affected by the acoustic properties of the venue itself. The waves reflect as a result of the different properties that it hits in the room. Certain venues, such as a cathedral, are constructed in such a way that the noises inside the building reverberate through the walls of the hall. In a music studio, however, the focus is to eliminate this reverberation, so as not to duplicate these echoes in the recording. First, it is necessary to control noise from heating or air conditioning systems within the studio (Rossing et. al 584). Moreover, recording studios should seek to absorb, rather than reflect, these sound waves. This can be accomplished through elements such as a thick carpet, heavily draped curtains, or diffuser panels (Lowery 71). Walls, for example, should not be parallel to avoid reflexivity. Likewise, building the studio in irregular shapes reduces and distributes resonance frequencies. Finally, it is important to create a path length between the microphone that keeps sound reflections at a minimum and creates the required intimacy between the performer and the microphone (Rossing et. al 583-4). These factors all contribute to minimizing external and internal sound.
Taking into account these aspects of recording studios, one must also consider the performer and the recorded music when constructing a studio. Aside from eliminating external and internal noise from the studio, there must be some consideration in making the musician comfortable when performing a vocal piece. Some ways this is accomplished is by giving life to the studio and by creating studios of a comfortable size (Newell 166). Moreover, when recording a vocal piece by an individual performer, close microphones help to foster intimate recording, and can later be using for mixing and mastering in post production (Rossing et. al 584). Private vocal booths also isolate noise even further and can enhance solo vocalists. These efforts all create a dampening effect upon the sound of the vocalist. It creates a shorter period, and lends more clarity in vocal performances. Yet, this reverberation period should not be zero, so as not to create a dead environment and foster a livelier performance with slight sound vibration and lingering of voice (Lowery 74). Specifically in such a studio, waves of short wave-length, or high pitch vocal notes, are more easily absorbed than long wave-lengths, or low pitch vocal notes (Lowery 72). One negative aspect of vocal performances in the studio is the quicker loss of these notes, creating a greater need on part of the performer to compensate for these tones and recreate liveliness in his or her singing.
These considerations of vocal performance in recording studios, however, greatly differ from the acoustics taken into consideration in concert halls. Like recording studios, reverberation is a huge issue when taking concert hall acoustics into account. While the general principles to minimizing reverberation still apply, such as lowering the sound of heat and air conditioning systems, there are other factors to consider in concert halls. The original sound reflects around the room based on the geometry, volume, materials, audience, and other factors of the hall. For example, one human body in the audience can be equivalent to one square meter of an open window (Allday 251). In such a situation, upholstered seats are a good option to absorb the sound of the audience and negate their acoustic difference. Plasters on the walls and ceilings are also good ideas to reduce reverberation.
In addition to these elements, in a concert hall, there are factors that a listener considers important in hearing and observing a performance. Intimacy, spaciousness, liveness, listener envelopment, clarity, and spatial impression are some important criteria for concert halls (Rossing et. al 535-7). Even in these categories, one can see the greater focus placed on resonance in a concert hall, and the effort to create the impression of “reverberant sound [that] appears to come from all directions” (Rossing et. al 537). Echoes and successive echoes, however, are to be avoided, and can be done so by avoiding parallel walls. Focusing sound in some areas of the concert hall can also be prevented by not using large concave surfaces where sound waves tend to focus and reflect (Rossing et. al 537). These external conditions all have an impact upon the individual performance.
In the specific case of a vocal performance, versus a primarily instrumental ensemble (such as an orchestra or a band), a shorter reverberation period is required. This is because vocal clarity is important in singing, such that words are discernible and successive sounds do not blend together (Allday 251). Yet, a certain amount of lingering in vocal performance may also create the desired musical effect the performer intends. Like in a music studio, a hall with excessive absorption will create a short reverberation period, yet will also make high pitch notes with shorter wave-lengths the first to be absorbed. Similarly, the performer must compensate for the loss of liveness in his performance. Especially in concert halls, there must be a balance between constructing acoustics for clarity and for liveness. Liveness can be enhanced by removing some of the heavy absorptive material from the hall such as thick carpets or curtains. Extensive hard reflective surfaces are recommended, which allow for additional absorbing plasters and panels that can modify reverberation (Lowery 76). Ultimately, a vocalist must adapt to the conditions of the hall in which he or she performs. In a resonant hall, the role of the performer is sometimes singing slower such that the words and notes resonate clearer among the audience. Solo vocal performers must especially take into account any deadening effects upon their voice, such as curtain or carpet absorption. In such a case, the performer should stand further forward on the stage and off of carpet to reduce overshadowing the voice.
Singing in a recording studio and a concert hall require different acoustical properties in creating a desired musical effect. The properties of vocal performance are distinguished from that of musical instrument alone, as words need to have a greater degree of clarity. This facet mediates the acoustical properties for singing venues and the efforts of the performer to adapt to different venues. In both a studio and a concert hall, there is emphasis placed on minimizing reverberation yet maintaining liveness. In a studio, there is greater effort to silence outside noises and avoid echoes, whereas in halls, reverberation is more evident to create an enveloping sound for the audience. Singing in both studios and halls, however, show how acoustics can alter even the simplest vocal performances through outside properties.
- Allday, Jonathan. Salters Horners advanced physics. Volume 2 of Salters Horners Advanced Physics Series. Oxford: Heinemann, 2001.
- Howard, David M., and Jamie Angus. Acoustics and Psychoacoustics. Music technology series. Oxford: Focal Press, 2001.
- Lowery, H. A Guide to Musical Acoustics. New York: Dover Publications, 1966.
- Newell, Philip. Recording Studio Design. Burlington, MA: Focal Press, 2007.
- Rossing, Thomas, Richard Moore , and Paul Weeler. Science of Sound. 3rd ed. San Francisco: Pearson Education, Inc., 2002.
- Vennard, William. Singing; The Mechanism and the Technic. New York: C. Fischer, 1967.