Filter
Top Products
99 Speech Intelligibility
Selecting STI scale or CIS scale
Models SE and DL
STI scale
The scale identifies if the mass notification system is intelligible or unintelligible based
on a STI scale ranging from 0.0 to 1.0 where 0.5 to 1.0 is considered a passing
score, per NFPA 72 and IEC 60849.
Common Intelligibility Scale (CIS)
Similar to the STI scale, the CIS scale uses a range from 0.0 to 1.0 to determine if the
MNS is intelligible. However, with the CIS scale, a rating of 0.7 to 1.0 is an
“intelligible” score, per the IEC 608489 and NFPA 72.
When to take STI-PA readings?
Scenario one
You may be able to run the test signal through the PA system during normal
business hours. In this scenario, you would set the meter to STI-PA and select either
STI scale or CIS scale and run your study in the mapped “zone” areas.
Scenario two
In other situations, running a test tone through a PA system during business hours
could be distracting and not feasible for your environment. In this situation, it is
recommended to follow these procedures:
• First, take sample background noise measurements during business hours.
These are saved and stored on the Verifier as “Captured Curves”. The verifier
will save up to four “captured curves”
• Second, in the STI-PA options, select the appropriate captured curve.
• Third, run your measurements at the appropriate time of day (i.e., late
evening/early morning). (The applied captured curve will automatically factor
into your study.)
• Fourth, view your results on the display of the instrument (or in Excel by using
the File converter tool.)
STI
00 - 0.30 0.3 - 0.45 0.45 - 0.60 0.60 - 0.75 0.75 - 1.00
scale
Unacceptable Poor Fair Good
Excellent
CIS
00-0.48
0.48 - 0.65
0.65 - 0.78 0.78 - 0.88 0.88 - 1.0
scale
Bad Poor Fair Good
Excellent