2. Acousteen, Herman Steeneken 1 Past, Present and Future of STI Herman J. M. Steeneken (www.steeneken.com)

3. Acousteen, Herman Steeneken 2 Past: STI (1971, 1980), Envelope Spectrum (1972), MTF (1975), RASTI (1979), prediction by ray-tracing (1981), IEC 60268-16 (1988, 1998) Present: Revised STI (1992, 1999, 2002), STIPA (2001), IEC 60268-16 (2003), ISO 9921 (2003) New and Future: B inaural STI, improvement measurement STI from speech signal, non-native speech, vocoders

4. Acousteen, Herman Steeneken 3 Signal-to-Noise ratio !!!

5. Acousteen, Herman Steeneken 4 Assessment Methods Subjective assessment with subjects (speakers and listeners): representative, limited reproduction, no diagnostics, laborious Objective assessment based on physical properties (measurements): reproducible, diagnostic, fast Objective methods allow prediction of system performance: design tool

6. Acousteen, Herman Steeneken 5 Speech and Noise

7. Acousteen, Herman Steeneken 6 Speech envelope function and envelope spectrum

8. Acousteen, Herman Steeneken 7 Spatial line frequency equivalent to MTF

9. Acousteen, Herman Steeneken 8 Distortion of Speech Envelope

10. Acousteen, Herman Steeneken 9 Dynamic measurement of SNR

11. Acousteen, Herman Steeneken 10 Matrix for seven MTF’s 1 Hz X 3 Hz 10 Hz

12. Acousteen, Herman Steeneken 11 CALCULATION of STI

13. Acousteen, Herman Steeneken 12 Calculation scheme

14. Acousteen, Herman Steeneken 13 Frequency weightings (various studies)

15. Acousteen, Herman Steeneken 14 Redundancy with image detection

16. Acousteen, Herman Steeneken 15 Frequency weightings (CVC words)

17. Acousteen, Herman Steeneken 16 Relation Noise and Band-pass limiting S.d.= 4.4% Male speech

18. Acousteen, Herman Steeneken 17 Listening test with four subjects

19. Acousteen, Herman Steeneken 18 Embedded CVC words: versta des over en nu fijs uit het woord zek einde noteer lal punt “Semi random” combination of: 17 initial consonants 15 vowels 11 final consonants

20. Acousteen, Herman Steeneken 19 Relation AGC and echoes S.d.= 6.9 % Male speech

21. Acousteen, Herman Steeneken 20 Qualification of STI (Acustica, 1984)

22. Acousteen, Herman Steeneken 21 Performance cabin public address

23. Acousteen, Herman Steeneken 22 Iso-STI contours

24. Acousteen, Herman Steeneken 23 Effective gain of a PA-system

25. Acousteen, Herman Steeneken 24 Field measurement

26. Acousteen, Herman Steeneken 25 Full STI (STI-14 and limited modulation frequency range STI-3) STI-14 Seven octave bands 14 Modulation frequencies Random envelope for octaves not under test STI-3 Seven octaves 3 Modulation frequencies (1.0, 3.15, and 10 Hz) Random envelope for octaves not under test

27. Acousteen, Herman Steeneken 26 RASTI (Room Acoustics STI,1979) Only for person-to-person communication assessment Two octave bands (500Hz and 2 kHz) Complex envelope (4 and 5 mod. freq.) see Acustica 1984, IEC 60268-16

28. Acousteen, Herman Steeneken 27 STI-PA (STI Public Address, 2001) Assessment of Public Address including: acoustic environment, band-pass limiting, overload dis- tortion Seven octave bands (125 Hz and 250 Hz merged) Complex envelope (2 simultaneous modulation frequencies per band) see IEC 60268-16

29. Acousteen, Herman Steeneken 28 Future Binaural STI Improvement using Speech as test signal Non-native talkers and listeners

30. Acousteen, Herman Steeneken 29 Future: Binaural STI (I) Use artificial head and perform simultaneous measurement on both ears Select highest performance (best ear selection) Use cross correlation approach for 500, 1000, and 2000 Hz.

31. Acousteen, Herman Steeneken 30 Future: Binaural STI (II)

32. Acousteen, Herman Steeneken 31 Future: improvement Speech Signal as test signal

33. Acousteen, Herman Steeneken 32 Future: n on-native talkers and listeners

34. Acousteen, Herman Steeneken 33 Conclusions STI predicts the speech intelligibility for many types of distortion: noise, band-pass limiting, non-linearity's, temporal, vocoding, non-native speech, and binaural hearing. Improvements (measuring methods or scope) of STI will not change the qualification ranges. STI is an international standardized method (ISO9921, IEC 60268-16) and used for many national standards.