1. Acousteen Herman J.M. Steeneken Standardization of the Speech Transmission Index Herman J.M. Steeneken Former convenor: ISO TC159/SC5/WG3, CEN TC 122/WG8

2. Acousteen Herman J.M. Steeneken Overview Workgroup Activities Scope and Field of Application of “ISO-9921” Criteria for Speech Communication Quality Assessment Methods Prediction methods Conclusions

3. Acousteen Herman J.M. Steeneken Workgroup activities (ISO, IEC) Standardisation of acoustical warning signals, (review ISO-7731, FDIS 2002, CEN standard next) Standardisation of Speech Transmission Quality, (review ISO-9921, FDIS 2002, CEN standard next) Standardisation of Speech Transmission Index, (review IEC-60268-16, CDV 2002) Standardisation of Sound systems for emergency purposes (review IEC 60849, CDV 2002)

4. Acousteen Herman J.M. Steeneken Scope and Field of Applications of ISO-9921 Criteria for speech communication quality - to be understood by designers and responsible people - sub-divided into representative groups of applications Assessment methods (simple and advanced) Prediction methods (related to assessment)

5. Acousteen Herman J.M. Steeneken Criteria for Speech Communication Quality Measures: Speech Intelligibility Vocal effort of speaker Applications: Alert and warning poorloud Person-to-person (critical)fairloud Person-to-person (relaxed)goodnormal Public address in public areasfairnormal Personal comm. systemsfairnormal

6. Acousteen Herman J.M. Steeneken Assessment Methods Subjective Assessment Mean Opinion Scoressimple Sentence Intelligibilitysimple (embedded) Word listsadvanced Objective Assessment Speech Interference Level (SIL)simple Speech Transmission Index (STI)advanced Speech Intelligibility Index (SII)

7. Acousteen Herman J.M. Steeneken Relation between subj. and obj. intelligibility measures Qualif. Sent. % CVC % PB % STI L SA – L LN SII nonsense meaning dB Excellent 100 >81 > 98 >0.75>21>0.75 Good 100 70-81 93-98 0.60-0.75 15 - 21 Fair 100 53-70 80-93 0.45-0.60 10 - 15 Poor 70-100 31-53 60-80 0.30-0.453 - 10<0.45 Bad <70 <31 <60 < 0.30 < 3

8. Acousteen Herman J.M. Steeneken Qualification and relation between subjective measures and STI

9. Acousteen Herman J.M. Steeneken Common Intelligibility Scale, CIS Barnett and Knight, IOA 1994 CIS not linear with SNR = STI  = 100 - ALcons x = AI  = PB words (256 words)  = Short Sentences = PB words (1000 words)  = 1000 syllables

10. Acousteen Herman J.M. Steeneken Relation STI versus SII r = 0.93

11. Acousteen Herman J.M. Steeneken Relation SIL versus STI/SII r = 0.97 (STI) r = 0.95 (SII)

12. Acousteen Herman J.M. Steeneken Criteria in ISO-9921and IEC 60849 Application Intell. SIL STI (CIS) Vocal dB effort Alert and warning (simple) poor 8 0.40 0.6 Loud Alert and warning (critical) fair 11 0.50 0.7 Loud Person-to-person (critical) fair 11 0.50 0.7 Loud Person-to-person (relaxed) good 15 0.60 0.8 Normal Public address in public areas fair 11 0.50 0.7 Normal Personal communication fair 11 0.50 0.7 Normal

13. Acousteen Herman J.M. Steeneken Prediction Methods SIL, vocal effort, noise (ISO-9921) STI, vocal effort, gender speaker,noise, band-pass limiting, masking, reverberation, echoes, non-linearity, (IEC 60268-16) SII, vocal effort, noise, band-pass limiting, masking, (ANSI 3 5.2)

14. Acousteen Herman J.M. Steeneken Calibration (Proposed) Reference speech signals at well defined conditions (through internet) Standardized spread sheets to calculate objective measures Specific software to process digital speech samples for listening tests

15. Acousteen Herman J.M. Steeneken Conclusions Increasing interest in verbal warning systems Revised standards on “ergonomic assessment of speech communication”, alarm and warning systems, all STI methods To be used by decision makers and designers Criteria, Assessment methods, and Prediction methods included