CONTENTS

 1     Scope
 2     References
 3     Definitions and abbreviations
 4     Convergence Performance of Echo Cancellers
        4.1     Speech Quality Degradation Perceived Subjectively
        4.2     Related Objective Parameters for Single Talk Mode
        4.3     Analysis Methods
                  4.3.1     Convergence Time (T_c) Test Method
                  4.3.2     Echo return loss, temporally weighted (ERL_tst) – single talk
 5     Speech Quality Evaluations during Double Talk
        5.1     Speech Quality Degradation Perceived Subjectively
        5.2     Related Objective Parameters
        5.3     Analysis Methods
                  5.3.1     CSS double talk method
                  5.3.2     Double talk testing using parallel combined sequences
 6     Companding and AGC Characteristics
        6.1     Speech Quality Degradation Perceived Subjectively
        6.2     Related Objective Parameter
        6.3     Analysis Methods
 7     Quality of Background Noise Transmission
        7.1     Quality Degradation Perceived Subjectively
        7.2     Related Objective Parameter
        7.3     Analysis Methods
 8     Switching Characteristics
        8.1     Speech Quality Degradation Perceived Subjectively
        8.2     Related Objective Parameters
        8.3     Analysis Methods
                  8.3.1     Attenuation Range and Switching Characteristics
                  8.3.2     Threshold Level and Build-Up Time (for Minimum Activation Level)
                  8.3.3     Hangover time
                  8.3.4     Threshold Level and Switching Time to Switch Over from RCV to SND (SND to RCV)
                  8.3.5     Switching Characteristics in the Presence of Background Noise
Annex A – Detailed Test Methodology for Temporally Weighted ERL_t
        A.1     Echo Return Loss Algorithm
                  A.1.1     Echo Return Loss, Temporally Weighted (ERL_t)
                  A.1.2     Modelling Echo Audibility
                  A.1.3     Expressing ERL_t Results
                  A.1.4     ERL_t Test Algorithm
Annex B – Double talk measurement filters for Method A
Annex C – Training Sequence Description
        C.1     Canceller Training prior to Double Talk
                  C.1.1     Double Talk Training Activity Masks
                  C.1.2     Synchronizing the Double Talk Training Activity Masks
                  C.1.3     Compensating for Measurement Filters
Appendix I – Bibliographic references
Appendix II – Example Evaluations
       II.1     Some Example Evaluations according to clause 5
                 II.1.1     Frequency Responses During Double Talk
                 II.1.2     Level Variations During Double Talk
                 II.1.3     Switching During Double Talk