BS 6840-16(1998) : 1998

1 Scope
2 Normative references
3 Definitions and abbreviations
4 Descriptions of the methods
    4.1 General
    4.2 The STI method
          4.2.1 General
          4.2.2 Precision of the STI method
          4.2.3 Limitations of the STI method
    4.3 The STITEL method
          4.3.1 General
          4.3.2 Precision of the STITEL method
          4.3.3 Limitations of the STITEL method
    4.4 The RASTI method
          4.4.1 General
          4.4.2 Precision of the RASTI method
          4.4.3 Limitations of the STITEL method
    4.5 Methods of measurement
          4.5.1 Method of measurement using an acoustic
                  excitation signal
          4.5.2 Method of measurement using direct (electrical)
                  injection of the test signal
          4.5.3 Simulation of occupancy noise
          4.5.4 Intelligibility tests using maximum length
                  sequence (MLS) analysis equipment
          4.5.5 Simulation of occupancy noise
          4.5.6 Repetition of measurements
          4.5.7 Analysis and interpretation of the results
5 Other methods of determining intelligibility
    5.1 Phonetically balanced word scores (256 or 1000
          population)
    5.2 Modified rhyme tests
    5.3 Articulation index
    5.4 Articulation loss of consonants
Annex A (normative) Speech transmission index (STI) and revised
(STI) methods
Annex B (informative) The STITEL method
Annex C (informative) The RASTI method
Annex D (informative) Estimating the correction in the case of
strong reflections
Annex E (informative) Bibliography

Deals with objectives procedures for rating the transmission quality of speech with respect to intelligibility. These three closely related procedures are known as the 'STI', 'STITEL', and 'RASTI' procedures and are intended for rating of speech transmission with or without sound systems. Includes a procedure for determination of speech intelligibility, together with a procedure for correlating the results of different methods of determination. ALSO NUMBERED AS BS EN 60268-16: 1998