NTi Audio Acoustilyzer AL1 - Manual (Page 59)

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e. STI-PA Error Detection
The Acoustilyzer STI-PA measurement function has a built in error detection
which helps you identifying faulty measurements. The error detection
checks the following parameters:
• Invalid modulation indices (MF1 or MF2 > 1.3)
• Irregularities during ongoing measurements
Both parameters depend on the amount of impulsive environmental noise.
Impulsive environmental noise influences the accuracy of any STI-PA
measurement.
If the error detection finds any problem,
the common STI-PA test result display is
interrupted with flashing “?.??” question
marks.
This error indication might be caused either
by
• missing test signal level, or
• impulsive background noise events
Detailed test result screen
The octave bands detected with
irregularities, are marked with a question
mark (?).
Recommendation
If the error detection finds any faults,
NTi Audio recommends you repeat the
measurement and compare the STI test
result with the previous ones.