130920 fire alarm_intelligibility[1]

Sharing our Guidance

X

Fire Alarm Intelligibility

• Define Intelligibility

• Code History of Intelligibility

• Current Intelligibility Requirements

• How to design for Intelligibility

• How to test for Intelligibility

Agenda

04/12/23 2

X

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

04/12/23 3

X

Fire Alarm Intelligibility

What Drives Intelligibility

04/12/23 4

• 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

X

Fire Alarm Intelligibility

History of Intelligibility in NFPA 72

04/12/23 5

• 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.

X

Fire Alarm Intelligibility

History of Intelligibility in NFPA 72

04/12/23 6

• 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.

X

Fire Alarm Intelligibility

Understanding Voice Intelligibility

04/12/23 7

• Important building characteristics:

• Occupancy type.

• Ceiling height.

• Surface features.

• Factors to talker/listener transmission path.

X

Fire Alarm Intelligibility

What affects Intelligibility

04/12/23 8

• 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.

X

Fire Alarm Intelligibility

Other Factor

04/12/23 9

• Room Geometry and Dimensions

• Furnishing and decorations

• Building occupant activities

• HVAC system noise

• Traffic noise

• The listener.

• Location and Distance from speaker.

X

Fire Alarm Intelligibility

Design for Intelligibility

04/12/23 10

• 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.

X

Fire Alarm Intelligibility

Speaker Spaces

04/12/23 11

• 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.

X

Fire Alarm Intelligibility

Speaker Spacing Example

04/12/23 12

X

Fire Alarm Intelligibility

Speaker Coverage Example

04/12/23 13

X

Fire Alarm Intelligibility

Testing For Intelligibility

04/12/23 14

• 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

X

Fire Alarm Intelligibility

Intelligibility Meter Examples

04/12/23 15

Lighting ControlCONCLUSION . . .

THANK YOU.