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6-1
This chapter covers a design methodology that can be used to design a speaker system for an
emergency voice/alarm communications system.
The ability to design an emergency voice/alarm communications system which is highly
intelligible at a reasonable cost, represents a significant advantage to the customer. Achieving an
acceptable level of intelligibility by trial and error can be extremely costly. A systematic approach
to the design using basic guidelines and simple models can yield excellent results with a minimum
investment of time.
It is important to understand the physical and acoustical characteristics of the space in which the
system is installed. This requires rough measurements or estimates of the dimensions of the space
and basic acoustical characteristics of the surfaces and furnishings. These factors determine the
reverberation time which influences intelligibility. More sophisticated modeling tools provide
accurate predictions of the reverberation time at any location within the modeled space. Simple
calculations however, provide reasonably accurate assessments that are more than adequate for
most installations.
Longer reverberation times require more care in the system design and even acoustical treatments
to be applied to the room to achieve acceptable levels of speech intelligibility. The lower the
reverberation time, the easier it is to provide a system with highly intelligible speech messaging.
Many spaces requiring emergency voice/alarm communications systems inherently have low
reverberation such as office buildings, retail stores, etc. Acoustical treatments are rarely required
and normal speaker layout rules apply. Churches, train stations, airport, etc. on the other hand
usually have high reverberation times and can require very special techniques to achieve
acceptable intelligibility levels. The sophisticated modeling tools may be required in these
instances.
For most cases a simple calculation of reverberation time can be helpful. Once the acoustical
characteristics of the room are understood, the speaker layout can be achieved.
Refer to the page number listed in this table for information on a specific topic:
Topic See Page #
Design Method 6-2
Recommendations for Maximizing System Intelligibility 6-3
Applying the Methods 6-4
Conclusion 6-13
Chapter 6
Speaker System Design Method
Introduction
In this Chapter