In an acoustically untreated space, such as the described council chamber, sound will reflect off

hard surfaces, creating high reverberation that degrades speech intelligibility. The primary

strategy to overcome this is to maximize the direct sound reaching the listeners while minimizing

the sound energy that excites the reverberant field. A narrow beam loudspeaker achieves this by

focusing sound precisely onto the audience area and away from reflective walls and ceilings. This

improves the direct-to-reverberant sound ratio, which is a critical factor for achieving optimal

speech intelligibility in challenging acoustic environments.

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1. AVIXA International. (2020). CTS-D Certified Technology Specialist-Design Exam Guide, Third

Edition. McGraw-Hill. In Chapter 5, "Creating AV Solutions," the guide explains that in highly

reverberant spaces, a loudspeaker with a narrow coverage pattern is used to keep sound energy

off reflective surfaces to improve intelligibility.

2. Long, M. (2014). Architectural Acoustics (2nd ed.). Academic Press (Elsevier). Chapter 14,

"Sound Systems," discusses how high-directivity (i.e., narrow beam) loudspeakers increase the

direct-to-reverberant sound ratio, which is essential for maintaining speech intelligibility in

reverberant rooms (pp. 665-668).

3. Davis, D., & Patronis, A. (2013). Sound System Engineering (4th ed.). Focal Press. Chapter

15, "Speech Intelligibility," details how loudspeaker directivity (Q) is a fundamental parameter

used to control the acoustic environment and improve the direct-to-reverberant ratio for better

clarity.