130920 fire alarm_intelligibility[1]
TRANSCRIPT
Sharing our Guidance
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Fire Alarm Intelligibility
• Define Intelligibility
• Code History of Intelligibility
• Current Intelligibility Requirements
• How to design for Intelligibility
• How to test for Intelligibility
Agenda
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Fire Alarm Intelligibility
• The capability of being understood or comprehended.
• In simple terms: Intelligibility is an evaluation of changes that occur to speech
that impact comprehension.
• More specifically: Intelligibility is concerned with evaluating reductions of
speech interruptions that cause undesired reduction in speech
comprehension.
What is Intelligibility
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Fire Alarm Intelligibility
What Drives Intelligibility
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• More detailed and involved Emergency communication systems
• High Rise buildings.
• Large Places of Assembly.
• Orderly and Safe Evacuation.
• NFPA 72:
• Voice Evacuation System.
• Emergency Communication System.
• UFC (Unified Facilities Criteria) 4-21-01
• Mass Notification System
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Fire Alarm Intelligibility
History of Intelligibility in NFPA 72
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• NFPA 72 - 1996
• Emergency Voice/Alarm Communication system with NO Intelligibility requirements.
• NFPA 72 - 1999:
• Addressed in Section 4-3.1.5 Communication system message with voice Intelligibility
• Voice Intelligibility should be measured in accordance with guidelines on Annex A of IEC 60849
second edition.
• NFPA -2002 and 2007
• Same basic criteria as 1999.
• Table 10.4.2.2 added testing methods.
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Fire Alarm Intelligibility
History of Intelligibility in NFPA 72
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• NFPA 72 2010:
• Section 18.4.1.5 Voice messages are not required to meet the audibility requirements,
but shall meet the intelligibility requirements Section 18.4.10.
• Section 18.4.10 within the system where intelligibility is required, voice
communication systems shall reproduce pre-recorded messages with voice
intelligibility.
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Fire Alarm Intelligibility
Understanding Voice Intelligibility
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• Important building characteristics:
• Occupancy type.
• Ceiling height.
• Surface features.
• Factors to talker/listener transmission path.
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Fire Alarm Intelligibility
What affects Intelligibility
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• Sound pressure level (loudness)
• Need to be loud enough to be heard.
• 15-20dB above ambient noise level.
• Reduce Echo:
• Construction material and obstructions.
• Speaker locations, wall or ceiling mounted.
• Reverberation (Re-Echo)
• If speakers are louder than necessary.
• Large rooms with no occupants or furniture.
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Fire Alarm Intelligibility
Other Factor
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• Room Geometry and Dimensions
• Furnishing and decorations
• Building occupant activities
• HVAC system noise
• Traffic noise
• The listener.
• Location and Distance from speaker.
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Fire Alarm Intelligibility
Design for Intelligibility
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• Use computer based software to design for Intelligibility
• Speaker Selection:
• Size.
• Construction.
• Frequency response.
• Audibility
• Speaker spacing and Placement
• Sound Pressure levels
• Dealing with Echo and Reverberation.
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Fire Alarm Intelligibility
Speaker Spaces
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• General Guidelines For speaker layout
• Speakers should be spaces at 2x the ceiling height.
• Selecting the right wattage.
• Selecting the right speaker type
• 15-20 dB above ambient noise of room.
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Fire Alarm Intelligibility
Speaker Spacing Example
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Fire Alarm Intelligibility
Speaker Coverage Example
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Fire Alarm Intelligibility
Testing For Intelligibility
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• Follow Testing Protocol : Per NFPA 72 Follow ISO 7240-19 Released 8/19/08
• Replaced IEC 60849
• Balanced Word Scores: 256 to 1000 words to a panel of listeners.
• Rhyme test to a panel of listeners.
• Digital Speech Meter:
• Not s typical sound meter
• Factors in the result the effects of room acoustics and background noise.
• Measurements conform to testing protocol standards
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Fire Alarm Intelligibility
Intelligibility Meter Examples
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Lighting ControlCONCLUSION . . .
THANK YOU.