Tyco 579-769 specifications Distributed Wall Mounted Systems

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Distributed Wall Mounted Systems

Introduction

The preceding sections apply primarily to ceiling mounted speakers, generally referred to as

 

“Distributed Overhead Systems.” Another useful mounting strategy is the “Distributed Wall

 

Mount System.” Under this configuration, the speakers are placed on walls or columns, and are

 

aimed into the room. Advantages and disadvantages of distributed wall mount systems are

 

described in the following sections.

Advantages

Disadvantages

For narrow areas such as hallways, fewer speakers and less amplifier power may be needed to cover the same size area. This is because all of the speaker’s sound contributes to useable audibility.

Mounting can be on more than one wall. This further improves the distribution of direct sound to the listener.

Wall mounted speakers put sound directly into the listener area. This can reduce the excitation of the reverberant field.

Combination speaker strobe units permit voice and visual notification in a single appliance.

The sound field from wall mount speakers is more likely to encounter obstructions from furnishings such as cubicle walls in office environments or movable partitions in conference rooms. If the furnishings in a room are likely to change, a distributed overhead system or a combination wall mount and overhead design should be considered. This minimizes the variation of audibility and intelligibility.

In rooms with low, hard ceilings the sound emitting from the top hemisphere of the coverage pattern is reflected off the ceiling and down to the listener. This can increase the reverberant field sound level and result in delayed arrival of sound. These factors both contribute to a reduction in intelligibility.

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Contents Fire Alarm Audio Applications Guide Page Copyrights and Trademarks Page Table of Contents Emergency Voice/Alarm Communications Systems Glossary of Terms Related Publications Chapter Speech Intelligibility Overview Speech Intelligibility Importance Designing for Chapter Background Information Topic See Page #Equation 2-1. The Decibel Equation 2-3. Power RelationshipsBasic Audio Math Equation 2-2. Ohm’s LawEquation 2-5. dB and Sound Pressure Levels Equation 2-6. Adding DecibelsSound and Hearing Robinson and Dadson Equal Loudness CurvesNature of Speech Speech Pattern that Illustrates ModulationsRoom Acoustics Sabine Equation, used when α Eyring Equation, used when αAreas with high ceilings, specify a more directional speaker Speaker Basics Equation 2-8. The Inverse Square LawSPL = Sensitivity + 20 log Equation 2-9. On-Axis SPL CalculationEquation 2-10. Directivity Factor Q for a Conical Source 6dB/division87dB 51º 104 Critical Polar Angle CalculationsEquation 2-11. Coverage Area Calculations Listener Height = 1.5 Meters Ceiling Coverage Diameter2x Edge-to-Edge Layout Pattern Selection GuideSPL Variation by Layout Pattern Minimum OverlapDistributed Wall Mounted Systems Wall Mounted Speakers In Meters Room Coverage Width WidthOpposite Speaker Edge-edge Minimum-Overlap Full-Overlap Chapter Speech Intelligibility Influences on Intelligibility Frequency of Speech Contribution to IntelligibilityDegradation of CIS vs. Signal-to-Noise Ratio No Noise With Added NoiseBackground Noise Reverberation Distortion ALcons Measures of IntelligibilityCorrelation of CIS and with STI and %ALcons STI method with faster measurement times Practical Measurement of Intelligibility STI-CIS Analyzer TalkboxTools for Predicting Intelligibility Page Chapter Emergency Voice/Alarm Communications Systems Typical Emergency Voice/Alarm Communications System AdvantagesParts of an Emergency Voice/Alarm Communications System Class a and B Speaker Circuit Wiring Chapter Regulatory Issues Audibility From Nfpa 72, 2002 EditionHigh Background Noise Large Areas Intelligibility Intelligibility Certification Page Chapter Speaker System Design Method Speaker Design Method Determine the speaker-to-listener distance D2Recommendations for Maximizing System Intelligibility Applying the Methods ITool Office Space ExampleOffice Space Speaker Location Guide Corridor Design Example Corridor Speaker Location Guide Corridor SPL DistributionITool Gymnasium Example 10. Gymnasium Speaker Location Guide 13. Lobby Example 15. Lobby Layout Applying the Methods Conclusion Page Chapter Glossary of Terms Glossary Glossary Page Index IN-2 Page 579-769 Rev. C