EN ISO 9921:2003

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Descriptions of speech communications
  4.1 General
  4.2 Speaker
  4.3 Transmission channel
  4.4 Listener
5 Performance of speech communications
  5.1 General
  5.2 Alert and warning situations
  5.3 Person-to-person communications
  5.4 Public address in public areas
  5.5 Personal communication systems
  5.6 Summary of recommended minimum performance
6 Assessment and prediction
  6.1 General
  6.2 Subjective assessment methods
  6.3 Objective assessment and prediction methods
Annex A (normative) Speaker and listener characteristics
Annex B (informative) Subjective speech-intelligibility
                      tests
Annex C (informative) Speech transmission index, STI
Annex D (informative) Overview of the means of
                      communication and related parameters
Annex E (normative) Speech interference level, SIL
Annex F (informative) Intelligibility ratings for
                      speech communications
Annex G (normative) Definition of symbols
Annex H (informative) Examples of applications of
                      predictive intelligibility methods
Bibliography

ISO 9921:2003 specifies the requirements for the performance of speech communication for verbal alert and danger signals, information messages, and speech communication in general. Methods to predict and to assess the performance in practical applications are described and examples are given.