1
Scope
2 References
3 Terms and definitions
4 Abbreviations and acronyms
5 Characteristics of VEDs
5.1 General
5.2 Acoustic echo control (AEC)
5.3 Noise reduction
(NR)
5.4 Tandem free operation
(TFO)
5.5 Interworking functions
(IWF)
6 Test signals
6.1 General
6.2 Measuring input and
output signal levels
6.3 Gaussian white noise
7 Tests
7.1 Overall VED tests
7.2 Noise reduction tests
7.3 Acoustic echo control
tests
Appendix I – Information on the function and location of VEDs in
mobile networks
I.1 VED functionality
I.2 VED location
I.3 CTM operation
Appendix II – Objective measures for the characterization of
the basic functioning of noise reduction algorithms
II.1 Introduction
II.2 Notations
II.3 Test signals
II.4 Objective measures for
characterization of NR algorithm effect
II.5 Recommendation values
for SNRI, TNLR and DSN
Appendix III – Properties of level measurement devices
III.1 Introduction
III.2 Measurement of signal
level
III.3 Transition time for
measurement device with exponential averaging
III.4 Transition time for
RMS measurement device
III.5 Comparing the levels
of two signals (exponential averaging)
III.6 Comparing the levels
of two signals (RMS method)
III.7 Artificial speech
signal in noise
III.8 Conclusions
Appendix IV – One-octave filters for the AEC comfort noise
test
IV.1 Introduction
IV.2 IIR realization
IV.3 FIR
realization
Bibliography