Tyco 579-769 specifications Practical Measurement of Intelligibility, STI-CIS Analyzer Talkbox

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Practical Measurement of Intelligibility

Introduction

AC Adapter

Measurement of intelligibility can be complicated, and it sometimes includes subjective analysis. To effectively implement intelligible systems in real buildings requires that a simple, accurate, and repeatable method of measuring intelligibility must be available. Fortunately, there are instruments on the market that meet this need. One of these is the STI-CIS meter available from SimplexGrinnell.

The meter uses the STIpa method to provide a fast and easy measurement of total system speech intelligibility. It measures both intelligibility and audibility, as it also has a built in dB meter. The meter automatically converts the STIpa measurement to CIS so that demonstrating that a system meets the requirements of NFPA 72 is easy and intuitive.

A proprietary test tone is played through the system which the analyzer uses to determine reduction in speech modulation.

STI-CIS Analyzer

Talkbox

Microphone

		Speaker
CD Player		Microphone
CD Player		Holder

STIpa

Test Tone CD

	AC Adapter	Volume
	AC Adapter	Control
		Control

Figure 3-5. STI-CIS Intelligibility Measurement System

3-8

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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 2-3. Power Relationships Basic Audio MathEquation 2-1. The Decibel 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 Calculation6dB/division 87dBEquation 2-10. Directivity Factor Q for a Conical Source 51º 104 Critical Polar Angle CalculationsEquation 2-11. Coverage Area Calculations Listener Height = 1.5 Meters Ceiling Coverage DiameterLayout Pattern Selection Guide SPL Variation by Layout Pattern2x Edge-to-Edge Minimum OverlapDistributed Wall Mounted Systems Width Opposite SpeakerWall Mounted Speakers In Meters Room Coverage Width 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 Measures of Intelligibility Correlation of CIS and with STI and %ALconsALcons 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