The STI panel is used to calculate the Speech Transmission Index for an impulse response by the indirect method per IEC 60268-16:2020. Post-processing (optionally including auditory masking) may be applied using noise and signal octave band levels which can be measured by REW or entered manually by double-clicking on the values in the table.
The Measure noise and Measure signal buttons allow Leq figures in each octave band to be measured with the Leq period set on the dialog. While measuring noise or signal levels the octave band figures will update in the table row and the overall LAeq figure will be shown. If the REW generator is used when measuring signal levels the IEC 60268-16:2020 speech-shaped noise signal will be automatically selected and ready to play.
To calculate STI for an impulse response that has been obtained through a sweep measurement select the measurement from the drop-down list and press Calculate STI. If post-processing is to be applied make sure the signal and noise level values have been measured or entered.
The results may be copied to the clipboard using the copy button.
The tables below list the theoretical and calculated m-values and the difference between them for each octave band per Appendix C.3.3 of the specification for the test signal listed. For all test signals with greater RT60 times the deviations were less than 0.001 and are not listed.
STIPA-expdecay-RT60=0.125.wav 125.0 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.999 0.999 0.998 0.997 0.995 0.992 0.988 0.982 0.971 0.955 0.931 0.894 0.846 0.781 0.000 0.000 0.000 0.000 0.001 0.001 0.002 0.003 0.004 0.007 0.010 0.016 0.023 0.034 250.0 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.999 0.999 0.998 0.997 0.996 0.993 0.990 0.984 0.974 0.960 0.938 0.906 0.862 0.805 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.002 0.003 0.005 0.007 0.010 500.0 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.961 0.941 0.909 0.868 0.813 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.001 0.002 0.002 1000.0 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 2000.0 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 4000.0 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 8000.0 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.999 0.999 0.998 0.997 0.996 0.994 0.990 0.984 0.975 0.962 0.941 0.910 0.869 0.815 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Maximum error 0.034 at 125.0 Hz, 12.5 Hz modulation