Voice evacuation systems can save lives in an emergency. The correct installation and periodic functional testing of such systems are therefore essential. The NTi Audio TalkBox and XL2 Sound Level Meter with the new extended background noise correction are instruments designed for this purpose.
The XL2 Sound Level Meter also considers, in real-time, the effect of background noise on the intelligibility of the announcement. This feature allows users to move efficiently through measure-adjust-measure cycles on site and immediately improve the speech intelligibility.
Professional verification of an evacuation system requires that the announcement level, the background noise level as well as the speech intelligibility values be measured and documented. An ideal measurement system for voice evacuation system verification is the XL2 Sound Level Meter in combination with the NTi Audio TalkBox. The TalkBox provides the reference sound source, playing the standardized speech intelligibility test signal into the announcement microphone. The handheld XL2 is then used, throughout the entire public area, to measure and store the sound level and speech intelligibility values.
Background noise can significantly affect the intelligibility of emergency announcements. It is sometimes impractical or even impossible to measure background noise at a location e.g. an as-yet unopened shopping center. In this case the expected ambient noise may be specified as a single broadband value such as between 70 and 80 dBA. In the XL2 Sound Level Meter this broadband noise level can now be directly defined within the instrument; the XL2 then compensates for this ambient noise when displaying the results. It is therefore possible to immediately make the necessary adjustments to improve speech intelligibility as required and measure again. This immediate feedback greatly simplifies and accelerates the process of optimization of voice evacuation announcement systems.
NTi Audio provides a free measurement report in MS Excel format for documentation of measurement results in multiple languages. The levels and frequencies for the announcement signal and the noise, as well as the determined STIPA speech intelligibility are reported for each measurement position.In the US, the requirements for evacuation systems are governed by the National Fire Alarm Code NFPA 72. In the UK, requirements are provided by the standard BS 5839-8. The speech intelligibility measurements are specified in the IEC 60268-16 standard. The NTi Audio measurement system for evacuation systems covers all relevant standards for a precise determination of sound levels and speech intelligibility.
All XL2 Sound Level Meters can be extended with the optional speech intelligibility measurements. The new features for extended speech intelligibility measurements are offered with firmware V3.03 or higher. This firmware is available to download for free by all registered XL2 customers.
More information about NTi’s Speech Intelligibility Test Solution is available here.
www.nti-audio.com
