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104 Speech Intelligibility
STI-PA results screens
Models SE and DL
2. Play the signal over the loudspeaker and then locate yourself in the
appropriate zone/room.
3. Verify that the range setting is appropriate for the level being measured. It
is desirable to select the longest range that does not overload. (To change
the range, press Up/Down Arrows from the STI-PA screen.)
4. Press the Run key to begin your study.
5. The meter will run for 15 seconds and then pause.
• To continue to take measurements, repeat step 3.
• To terminate your study, please see step 6.
6. Press the Stop key to end your study. (Three viewable results screens
are explained in the next section.)
STI-PA results screens
The test signal is made up of 7 octave band signals which encompasses a
combination of vowels and syllables from common speech. There are 14
modulating frequencies that emulate a male/female’s speech patterns. The STI
method is based on the determination of the modulation transfer function (MTF)
which is the ratio of measured modulation to the overall signal strength at each
modulation frequency.
Viewing STI-PA results
1. Once in pause or review mode, press repeatedly to toggle through
the STI-PA results screen.
STI-PA measurement and scale results screen
In the STI-PA measurement screen, the MTF is combined according to IEC 60268-
16 and presented on a scale between 0 to 1 representing the quality or intelligibility of
the mass notification system.
Figure 6-21: STI-PA measurement (scale results) screen
STI-PA scale results
STI-PA results
graphical view
Range