standardization of the speech transmission index
DESCRIPTION
Standardization of the Speech Transmission Index. Herman J.M. Steeneken Former convenor: ISO TC159/SC5/WG3, CEN TC 122/WG8. Overview. Workgroup Activities Scope and Field of Application of “ISO-9921” Criteria for Speech Communication Quality Assessment Methods Prediction methods - PowerPoint PPT PresentationTRANSCRIPT
Acousteen Herman J.M. Steeneken
Standardization of theSpeech Transmission Index
Herman J.M. Steeneken
Former convenor: ISO TC159/SC5/WG3, CEN TC 122/WG8
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
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)
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)
Acousteen Herman J.M. Steeneken
Criteria for Speech Communication Quality
Measures:Speech IntelligibilityVocal effort of speaker
Applications: Alert and warning poor loud Person-to-person (critical) fair loud Person-to-person (relaxed)good normal Public address in public areasfair normal Personal comm. systems fair normal
Acousteen Herman J.M. Steeneken
Assessment Methods
Subjective Assessment• Mean Opinion Scores simple• Sentence Intelligibility simple• (embedded) Word lists advanced
Objective Assessment•Speech Interference Level (SIL) simple•Speech Transmission Index (STI) advanced•Speech Intelligibility Index (SII)
Acousteen Herman J.M. Steeneken
Relation between subj. and obj. intelligibility measures
Qualif. Sent. % CVC % PB % STI LSA – LLN 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 0.30-0.45 3 - 10 <0.45
Bad <70 <31 <60 < 0.30 < 3
Acousteen Herman J.M. Steeneken
Qualification and relation between subjective measures and STI
Acousteen Herman J.M. Steeneken
Common Intelligibility Scale, CISBarnett 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
Acousteen Herman J.M. Steeneken
Relation STI versus SII
0
0,2
0,4
0,6
0,8
1
0 0,2 0,4 0,6 0,8 1
STI
SII
r = 0.93
Acousteen Herman J.M. Steeneken
Relation SIL versus STI/SII
0
0,2
0,4
0,6
0,8
1
-10 -5 0 5 10 15 20 25 30 35
LSA-LLN
STI
/ S
II
STI
SII
r = 0.97 (STI)r = 0.95 (SII)
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
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)
Acousteen Herman J.M. Steeneken
Calibration (Proposed)
• Reference speech signals at well definedconditions (through internet)
• Standardized spread sheets to calculate objective measures
• Specific software to process digital speech
samples for listening tests
Acousteen Herman J.M. Steeneken
Conclusions
• Increasing interest in verbal warning systems
• Revised standards on “ergonomic assessmentof speech communication”, alarm and warning
systems, all STI methods
• To be used by decision makers and designers
• Criteria, Assessment methods, and Predictionmethods included