STIPA Measurement

STIPA (Speech Transmission Index for Public Address systems) is a simplified, single-channel measurement method for STI defined in IEC 60268-16:2020 §5. It uses a specially designed modulated pink noise signal that simultaneously tests two modulation frequencies per octave band, providing a result that closely approximates the full STI value (typically within ±0.03). STIPA measurement requires a standardized signal played through the sound system under test and a STIPA-capable analyzer at the listener position. The measurement takes approximately 15 seconds per position. STIPA is the standard method for routine testing of public address and voice alarm systems in buildings, airports, railway stations, and stadiums. It captures the effects of loudspeaker quality, room acoustics, background noise, and signal processing on speech intelligibility. Regular STIPA testing is recommended for life-safety voice alarm systems and is required by some fire codes.