Commissioning & Inspection of Voice Evacuation Systems

XL2 STIPA Analyzer

Public Address (PA) systems in buildings like airports, railway stations, shopping centers, stadiums, or concert halls have to clearly inform persons in danger about escape information and directions in case of an emergency. People need to be given understandable instructions so they can react quickly and in an orderly fashion – a Life Safety Code requirement.

Using a hand-held instrument, it is possible to commission the entire building by measuring just how intelligible the PA announcements will be when comprehensibility will be most needed.

At a glance

  • Announcement Level
  • Speech Intelligibility STI
  • Compliant with EN 54-24, IEC 60268-16, IEC 50849, NFPA-72UFC 4-021-01, FEMA Technical Bulletin


The measurement of speech intelligibility provides useful information about the current status of the PA system. This leads to important conclusions for optimizing the system and improving the intelligibility. To do this, the following parameters must be assessed:

  • Announcement Level 
  • Background Noise
  • Speech Intelligibility

Announcement Level

XL2 Sound Level Meter

The announcement level should exceed the ambient sound pressure level by a minimum of 10 dB. Levels below this may make it more difficult to achieve a good speech intelligibility. This applies to all locations where emergency announcements are conveyed to the building occupants. The measured announcement level should not be less than 65 dBA nor more than 105 dBA at each listener position. A louder announcement is not always better; the speech intelligibility reduces gradually at levels exceeding 80 dBA.

The XL2 Sound Level Meter offers a powerful solution for commissioning and verifying voice evacuation installations. It measures the actual live level, the average level over time and the minimum/maximum announcement level. All results are automatically stored onto a removable SD card including the measurement position number. This saves valuable time later during documentation.

The announcement level measurement itself should take 60 seconds at each position in accordance with the ISO 7240 standard. If the PA system includes a microphone for spoken emergency announcements, the NTi Audio TalkBox serves as an excellent reference speaker. It plays pre-recorded announcements or customized messages at the recommended sound pressure level into the voice microphone, until you have completed the verification at all measurement positions. Your own announcement signals may be loaded onto the memory card and are seamlessly looped.


TalkBox Speaker Microphone

Background Noise

First, measure the typical background noise at your designated positions for a representative period (e.g. 30 seconds) and store the readings including the noise spectrum in octave band resolution. The speech intelligibility depends heavy on the signal noise ratio – thus you require this measurement later on for the ambient noise correction of the speech intelligibility assessment.

XL2 Sound Level Meter

Speech Intelligibility STI

The XL2 Analyzer, with the STIPA Option installed, measures the speech intelligibility according to the latest revision of standard IEC 60268-16:2020 (edition 5) and older editions. It offers ambient noise correction and automated averaging for repeated measurements. The XL2 displays the speech transmission index (STI) and the common intelligibility scale (CIS), accompanied by the individual levels and modulation indices of the seven octave bands.

XL2 STIPA Analyzer


  • Measurement in accordance with IEC 60268-16 (edition 2, 3 and 4)
  • Ambient Noise Correction
  • Automated Averaging
  • Display of Modulation Indices

Announcements by Persons

The NTi Audio TalkBox is required for audio systems with voice microphones. The TalkBox feeds the special speech intelligibility test signal into the operator microphone of sound reinforcement systems. It presents the standardized voice-like acoustic signal emission simulating a human talker according to IEC 60268-16, at standardized levels. This setup considers the entire signal path for an accurate STIPA measurement. It includes all effects of the operator's microphone and environment.

The TalkBox provides two major advantages for STIPA measurements:

  • An extended test coverage and an easy to handle test signal injection.
  • Sampling frequency deviations are completely eliminated - a dangerous trap when using portable CD players.

Prerecorded Announcements from Mass Storage Media

The Minirator MR-PRO is used as a test signal generator for electrical signal injection into public address systems that commonly use alarm messages from a hard drive (systems without a microphone).

Minirator MR-PRO

STI Reporting Tool

The STI Reporting Tool creates measurement reports according to the standards

  • AS 1670.4
  • CEN/TS 54-32:2015
  • DIN EN 50849:2017
  • IEC 60268-16
  • ISO 7240-19:2007
  • VDE V 0833-4-32:2016
  • VDE 0828-1:2017-11

The tool calculates the effect of the actual ambient noise caused by the public onto the measured speech intelligibility. Thus it provides you the expected speech intelligibility in STI or CIS during real-life emergency announcements.

STIPA Reporting Tool

System Requirements:

  • PC running Windows XP, 7, 8 and 10
  • Excel 2010, 2013 or 2016 (32 bit or 64 bit)

More about Speech Intelligibility


XL Set for STI-PA Testing

XL2 Kit for Commissioning & Inspection of Voice Evacuation Systems

  • XL2 Audio and Acoustic Analyzer
  • STIPA Option for XL2
  • M4261 Measurement Microphone
  • Minirator MR-PRO
  • ASD Cable for XL2
  • Cable Test Plug (MR-PRO)
  • 2x Mains Power Adapter
  • 3x Calibration Certificates
  • Exel System Case

Optional as required:


for announcements by persons

Calibration Certificate for TalkBox

Get more Information

Contact us for a quotation or to discuss your measurement application.

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