Page 25 - Winter 2008

SOUND SYSTEM DESIGN
Marshall Long
Marshall Long/Acoustics Sherman Oaks, California 91423
At the beginning of certain sound
system design projects there is a
moment of panic when the
whole thing seems totally impossible.
Usually the difficulties arise from a
combination of a challenging acousti-
cal environment and complicated client
demands. At these times it is useful to take a deep breath and review the overall design objectives, which are relative- ly simple: (1) distribute direct sound evenly to the listening area, (2) provide adequate intelligibility, (3) deliver suffi- cient level, frequency response, and natural sound quality for the intended use, (4) leave the listener with the sense that the sound is coming from the source, (5) control feed- back at the microphone positions, (6) avoid acoustical defects such as long delayed reflections, and (7) respect the architecture of the space.
Sound system design combines the arts of architecture, audio, and acoustical engineering and can be surprisingly complicated. The sound system designer is often asked to provide a solution in a less than ideal acoustic environment for a variety of potential uses. Figure 1 illustrates a good example of a challenging project. It is a sketch by the archi- tects, Armando Ruiz and Associates, of their concept of the reconfiguration of a traditional gothic chapel at Mount Saint Mary’s College, a small Catholic women’s college in Los
“Vendors should publish the formulas and assumptions behind their software.”
Angeles. The existing room had a cruci- form shape with wooden pews facing the sanctuary. The building has 40-foot- high arched ceilings and is built of stone and concrete with unpadded wooden pews and tile floors.
It is being redesigned to accommo- date services in the round in keeping with the Vatican II encyclical that encourages “full active and conscious participa- tion in the liturgy.” The existing pews will be removed, and a new seating configuration installed, which can be rearranged using moveable chairs, into any configuration to accommo- date various uses. In addition to traditional Masses with pre- senters located at six different locations distributed throughout the space, the room will be used for lectures, working group presentations, choral singing, and small musical ensembles.
Attendance can vary from 6 to 200 at any given time.
The transmission of speech over the existing sound sys- tem was difficult to understand, as was unamplified speech beyond about 20 feet. Organ and sacred music sounded won- derful over the existing sound system and the music director did not want to loose those special qualities. The architect wanted to preserve the existing visual ambience. Not surpris- ingly the budget was small and the time frame short. This project, which was completed in late 2006, serves as a good
example of the audio design process.
Fig. 1. Mount Saint Mary’s College Chapel.
Sound System Design 23