Acousteen, Herman Steeneken 1 Past, Present and Future of STI Herman J. M. Steeneken (
Acousteen, Herman Steeneken 2 Past: STI (1971, 1980), Envelope Spectrum (1972), MTF (1975), RASTI (1979), prediction by ray-tracing (1981), IEC (1988, 1998) Present: Revised STI (1992, 1999, 2002), STIPA (2001), IEC (2003), ISO 9921 (2003) New and Future: B inaural STI, improvement measurement STI from speech signal, non-native speech, vocoders
Acousteen, Herman Steeneken 3 Signal-to-Noise ratio !!!
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
Acousteen, Herman Steeneken 5 Speech and Noise
Acousteen, Herman Steeneken 6 Speech envelope function and envelope spectrum
Acousteen, Herman Steeneken 7 Spatial line frequency equivalent to MTF
Acousteen, Herman Steeneken 8 Distortion of Speech Envelope
Acousteen, Herman Steeneken 9 Dynamic measurement of SNR
Acousteen, Herman Steeneken 10 Matrix for seven MTF’s 1 Hz X 3 Hz 10 Hz
Acousteen, Herman Steeneken 11 CALCULATION of STI
Acousteen, Herman Steeneken 12 Calculation scheme
Acousteen, Herman Steeneken 13 Frequency weightings (various studies)
Acousteen, Herman Steeneken 14 Redundancy with image detection
Acousteen, Herman Steeneken 15 Frequency weightings (CVC words)
Acousteen, Herman Steeneken 16 Relation Noise and Band-pass limiting S.d.= 4.4% Male speech
Acousteen, Herman Steeneken 17 Listening test with four subjects
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
Acousteen, Herman Steeneken 19 Relation AGC and echoes S.d.= 6.9 % Male speech
Acousteen, Herman Steeneken 20 Qualification of STI (Acustica, 1984)
Acousteen, Herman Steeneken 21 Performance cabin public address
Acousteen, Herman Steeneken 22 Iso-STI contours
Acousteen, Herman Steeneken 23 Effective gain of a PA-system
Acousteen, Herman Steeneken 24 Field measurement
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
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
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
Acousteen, Herman Steeneken 28 Future Binaural STI Improvement using Speech as test signal Non-native talkers and listeners
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.
Acousteen, Herman Steeneken 30 Future: Binaural STI (II)
Acousteen, Herman Steeneken 31 Future: improvement Speech Signal as test signal
Acousteen, Herman Steeneken 32 Future: n on-native talkers and listeners
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 ) and used for many national standards.