CONTENTS

 1     Introduction
 2     Normative references
 3     Definitions and abbreviations
 4     Transmission characteristics
        4.1     Sending sensitivity
        4.2     Receiving sensitivity
        4.3     Frequency response curves
                  4.3.1     Sending
                  4.3.2     Receiving
        4.4     Subjective evaluations of loudness ratings
                  4.4.1     Sending
                  4.4.2     Receiving
        4.5     Objective evaluations of sensitivity and loudness ratings
                  4.5.1     Sensitivity measurement
                  4.5.2     Measure and computation of loudness ratings
        4.6     Switching parameters
 5     Testing conditions
        5.1     Test table
        5.2     Test arrangement
        5.3     Calibration of the artificial mouth
        5.4     Test environment
        5.5     Test signals
        5.6     Test signal levels
 6     Conversational quality
 7     Parameters measured instrumentally
        7.1     Attenuation range a_H
        7.2     Attenuation distribution at idle mode
        7.3     Hang-over time
        7.4     Dynamic compression
        7.5     Reverberance
        7.6     Time-dependent transfer function
        7.7     Duplex behaviour
        7.8     Control characteristics of echo cancellation
        7.9     Speech detection
       7.10     Speech detection with ambient noise
       7.11     Background noise transmission
 8     Behaviour of hands-free terminals in double talk situation
        8.1     Categorization
        8.2     Terminal coupling loss in double talk situation
 9     Parameters to be evaluated for each type of HFT
10     Acoustic echo controllers and speech enhancement devices
       10.1     Functional units
      10.2      Delay
                 10.2.1     Processing delay
                 10.2.2     Round trip echo path delay (EPDn) – network interface
       10.3     Acoustic echo control specifications
                 10.3.1     Acoustic echo path
                 10.3.2     Parameters and recommended limits
Annex A – Test results
        A.1     Categorization of hands-free terminals based on double talk performance
                  A.1.1     Results of the listening only tests with variable attenuations in sending path
                  A.1.2     Results of the listening only tests with variable attenuations in receiving path
                  A.1.3     Results of listening only tests on echo disturbance
        A.2     Relationship between Listening only tests, Double talk tests and Conversation tests: comparison of six different hands-free terminals
Appendix I – Preliminary values
        I.1     Double talk performance
        I.2     Build-up time characteristics
        I.3     Level adjustments by companding or AGC
Appendix II – Examples of processing delays for mobile hands-free terminal
       II.1     Example 1
Tadd_proc (additional time for processing)
       II.2     Example 2
Appendix III – Recommended test bed
      III.1     Example 1: Implemented test hybrid
      III.2     Example 2: Adaptive Echo Canceller
Appendix IV – Bibliography