Standards glossary
The words that decide whether a submittal is accepted
A short, working glossary for consultants, contractors and buyers. It is not a substitute for the standard text, but it keeps the conversation on the same terms.
The glossary is a design aid, not a legal interpretation of the standards.
1
100V line
A constant-voltage loudspeaker distribution method. The amplifier output is stepped up to 100V, and each loudspeaker has a transformer with a tap.
B
BGM
Background music. The everyday music function of a public-address system, usually at a low level and zoned by area.
C
Cardioid
A microphone or loudspeaker pickup pattern that favours the front and rejects the rear. Useful for feedback control.
Cause-and-effect matrix
The table that defines which fire alarm event triggers which evacuation zone, message and output.
D
Dante / AES67
Networked audio transport protocols. They are not the same as an IP public-address system, although they can coexist.
Delay loudspeaker
A loudspeaker placed further back in a room and delayed so that its sound arrives in step with the main system.
DSP
Digital signal processor. Used for equalisation, delay, limiting, routing and preset storage.
E
EN 54-16
The European product standard for voice-alarm control and indicating equipment.
EN 54-24
The European product standard for loudspeakers used in fire detection and fire alarm systems.
G
Gooseneck microphone
A flexible-stem microphone used on conference delegate units and lecterns.
H
Headroom
The difference between the connected load and the amplifier’s rated output, kept for programme peaks and ageing.
L
Line array
A vertical array of loudspeaker modules that gives controlled vertical coverage over a long throw.
Line loss
The voltage drop along a loudspeaker line. It increases with cable length and load; the cable size is chosen to keep it acceptable.
N
NFPA 72
The US National Fire Alarm and Signaling Code, which includes emergency communication and intelligibility requirements.
P
PA
Public address. Live and scheduled announcements to a building or site, usually through a zoned loudspeaker network.
PAVA
Public address and voice alarm. A combined system that provides both general announcements and fire evacuation.
R
RF coordination
Planning the frequencies and antenna placement of wireless microphones so that channels do not interfere.
RT60
Reverberation time: the time for sound to decay by 60 dB. Long RT60 makes speech harder to understand.
S
SIP
Session Initiation Protocol, used for VoIP and some paging/intercom integrations.
SPL
Sound pressure level, measured in decibels (dB). The design target is set at the listener, not at the loudspeaker.
Stage monitor
A loudspeaker aimed at the performer so they can hear the programme or their own voice.
STI
Speech transmission index. A measure of speech intelligibility from 0 to 1; higher is better. The target depends on the room use.
Subwoofer
A loudspeaker dedicated to low frequencies, used for music reinforcement.
T
Tap
The wattage setting on a loudspeaker transformer. A 3W tap draws less power and plays quieter than a 6W tap from the same line.
V
Voice alarm
The life-safety function that broadcasts evacuation messages. It overrides music and paging and is subject to fire standards.
Z
Zoning
Dividing the building into separately addressable audio areas for paging, music and evacuation.
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