1385Chapter 36
Designing for Speech Intelligibility
by Peter Mapp
36.1 Introduction........................................................................... 1387
36.2 Parameters Affecting Speech Intelligibility.................................................. 1387
36.3 The Nature of Speech................................................................... 1387
36.4 Factors Affecting Sound System Intelligibility................................................ 1388
36.4.1 Primary Factors Include.............................................................. 1388
36.4.2 Secondary Factors Include............................................................ 1388
36.5 System Frequency Response and Bandwidth................................................. 1388
36.6 Loudness and Signal-to-Noise Ratio........................................................ 1390
36.7 Reverberation Time and Direct-to- Reverberant Ratios......................................... 1393
36.7.1 Intelligibility Prediction—Statistical Methods............................................. 1395
36.7.2 Intelligibility and Reverberation Time................................................... 1397
36.8 Some Further Effects of Echoes and Late Reflections.......................................... 1397
36.9 Uniformity of Coverage................................................................. 1399
36.10 Computer Modeling and Intelligibility Prediction............................................ 1400
36.11 Equalization.......................................................................... 1400
36.12 Talker Articulation and Rate of Delivery................................................... 1401
36.13 Summary of Intelligibility Optimization Techniques.......................................... 1402
36.14 Intelligibility Criteria and Measurement.................................................... 1403
36.14.1 Subject-Based Measures and Techniques................................................ 1403
36.14.2 Objective Measures and Techniques.................................................... 1404
36.14.2.1 Articulation Index.............................................................. 1404
36.14.2.2 Articulation Loss of Consonants................................................... 1404
36.14.2.3 Direct-to-Reverberant and Early-to-Late Ratios....................................... 1404
36.14.2.4 Speech Transmission Index STI, RASTI, and STIPA................................... 1405
36.14.2.5 SII Speech Intelligibility Index.................................................... 1409
36.14.3 The Future for Speech Intelligibility Measurements........................................ 1409
Acknowledgments.......................................................................... 1410
Bibliography............................................................................... 1410