Professional STIPA (Speech Transmission Index for Public Address) measurement is the internationally standardised method for verifying that voice alarm and public address systems can transmit speech clearly enough to be understood by building occupants in an emergency. STIPA measurement per IEC 60268-16 is mandated by EN 54-16, BS 5839-8, ISO 7240-19, and IEC 60849 for voice alarm system commissioning, acceptance testing, and annual inspection. A minimum STI value of 0.50 ("Fair") at all critical listening positions is typically required for regulatory compliance.
Voice alarm systems are life-safety systems: in a fire or emergency, the PA system must be able to broadcast evacuation instructions that building occupants can understand clearly, even in the presence of background noise, reverberation, and crowd noise. STIPA measurement quantifies this speech intelligibility at representative listening positions throughout the building, providing an objective, standards-based measure of system performance that can be documented, audited, and used as evidence of compliance.
A valid STIPA measurement requires: (1) Connect talkbox to PA amplifier input at the correct level. (2) With PA system broadcasting STIPA test signal, position STIPA receiver at measurement point 1.2–1.6 m above floor level. (3) Record STI value for each measurement position. (4) Record background noise level at each position. (5) Document results, compare with required minimum STI value (typically 0.50), and prepare commissioning report. Repeat for all required measurement positions as defined by the applicable standard and project specification. For full methodology, read our STIPA Measurement Guide.
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