3M SE, DL user manual STI scale, Common Intelligibility Scale CIS, When to take STI-PA readings?

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Speech Intelligibility

Selecting STI scale or CIS scale

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.

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

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.

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

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.)

Models SE and DL