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Frequently Asked Questions

Speech Intelligibility Reporting Tool extended

Speech Intelligibility Reporting Tool extended
The XL2 Acoustic Analyzer reliably measures the Speech Transmission Index (STI). The results can be imported into the STI Reporting Tool to create professional measurement reports in accordance with the IEC 60268-16 standard. The report now also simplifies workflows by allowing you to assign the same ambient noise spectrum to multiple speech intelligibility measurement results.

The XL2 Acoustic Analyzer forms the standardized solution for portable speech intelligibility measurement of voice evacuation systems. The handheld instrument is tailored for quick testing on-site with the measurement results available to the operator in a matter of seconds.

Measurement performed at quiet Conditions
Measuring the speech intelligibility of life-safety installations under realistic environmental conditions is often not feasible. Playing the test signal in a railway station for example, will almost certainly disturb and irritate passengers. The measurement also requires that the ambient noise is constant which is also not easily achievable during the day with numerous other noise sources present. Under such circumstances the STI measurement with the XL2 Acoustic Analyzer is usually scheduled at a more suitable time of the day, e.g. night time when there are no passengers to disturb and the test is unaffected by other noise sources. In addition to the STI measurement at night the ambient noise spectrum is measured during the typical busy day. The XL2 then combines both measurements calculating the correct STI value by taking into account the typical day time ambient noise conditions at each of the measurement locations. Furthermore this calculation and the detailed analysis is also offered by the STI Reporting Tool on the computer.

Time-saving Ambient Noise Correction
All XL2 measurement results can be directly imported into the STI reporting form for detailed documentation. Additionally the form combines the STI measurement taken at quiet conditions and the actual ambient noise recorded during the day-time. This calculates the expected speech intelligibility value in real-life conditions. Many projects use a single ambient noise spectrum sample for the majority of the STI measurement positions. Therefore the applicable ambient noise spectrum can now directly be applied to multiple STI measurement positions. This simplification saves time in the data analysis and documentation of the project’s speech intelligibility.


The STI Reporting Tool is a free service for all registered XL2 customers.
Download the latest STI Reporting Tool here.
Read more about speech intelligibility measurements here.

Contact NTi Audio for more details here.



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