Sound Systems: Distributed Sound

Two most common types of gymnasium sound systems are central cluster and distributed. Both systems have strengths and weaknesses. This article will briefly discuss central cluster and then concentrate on the distributed speaker system.

Regardless of the type of sound system used, there are two primary requirements: First, the loudspeaker system must provide sound that is intelligible (understandable) despite a great deal of crowd noise. Second, this sound system will probably be used to reproduce a range of sounds, from speech to music (music puts a great deal of demands on a sound system).

The physical components must also meet two criteria: 1)They cannot detract from site lines of a game or concert. Plus, your gymnasium will be used for more than sporting events; so, you probably want them to look appealing. 2)They need to be protected. The speakers need to be housed in a protective case to protect them from stray volleyballs, basketballs, etc.

Central Cluster System

Figure 1

The components that make up a central cluster system are grouped together in one location (Figure 1). As discussed earlier, gymnasiums provide unique acoustical challenges. In order for a central cluster system to provide adequate sound to every seat in the gym, speakers with good pattern control must be used. This can make the "cluster" of components very large and expensive. In most cases this type of system hangs down from the ceiling, which makes it visible and unprotected from those high-flying volleyballs.

Distributed System

Figure 2

Distributed systems contain several identical or at least similar speaker components spread out or "distributed" throughout the room (Figure 2). Distributed loudspeaker systems have had a poor reputation for sound quality. Recently, loudspeaker manufacturers have greatly improved the products and maintained realistic prices. It is possible to design and install a distributed system with sound quality that rivals central cluster systems.

Benefits:

With distributed loudspeaker systems, the listener is relatively close to the loudspeaker. This means each loudspeaker can be simpler, smaller, lighter and usually less expensive. Distributed loudspeaker components are also easier for the architect or sound system contractor to "hide" in the room.

Figure 3

Figure 3 is a cross-section of a gym ceiling. Notice how the loudspeakers are installed in a suspended ceiling, which complements the cement ceiling structure. This approach protects the components and makes them almost invisible. This same approach can be used with existing gyms that may not allow major structural changes. Low-profile "box" speakers can be mounted at or near the ceiling. This will still provide more than adequate visual appeal and, using the right components, will minimize any physical obstruction problems.

The distributed speaker system can also be set up in "zones." These zones can be individually turned on or off. This allows you to adjust for different seating arrangements or athletic events. Turning off speakers in the unused areas will often result in better sound in the occupied seating.

Figure 4	Figure 5

Drawbacks:

One drawback to basic distributed systems is the lack of source localization. Source localization is the perception of the sound actually coming from the direction of the source, such as a person speaking (Figure 4). Since the distributed speaker components nearest the listener are usually much closer than the actual sound source is to the listener, the listener will obviously perceive that the sound is coming from the loudspeaker (Figure 5). This can be very distracting if the system is used with a musical or drama. The audience will find the sound unnatural if the reinforced sound comes from above them rather than from the stage. However, a complex system of speaker zones and electronic delays can even help achieve localization with distributed speakers.

Summary

In most if not all school buildings, the gymnasium is a multipurpose facility for a variety of functions. The sound system for this type of room is critical to realizing the full potential of the facility. An evaluation of all the uses and needs of the facility must be made. Then, a qualified, experienced sound system contractor or acoustical consultant can design the best solution for your specific gymnasium. Please contact us with any questions you may have regarding this important facet of your facility. We would welcome the opportunity to assist you in any way we can.

by Travis Ludwig © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

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