Question 8/XV - Characteristics of acoustic echo control equipment
(Continuation of Question 11/XV, 1985-1988)

Considering

(1) that acoustic echo control is now necessary in many areas of
telecommunication such as:

1.1 teleconferencing,

1.2 loudspeaking telephones,

1.3 mobile applications,

1.4 ISDN;

(2) that equipment used for acoustic echo control may utilize, in part,
the principles and techniques for echo control given in Recommendations
G.164 and G.165;

(3) that a draft Recommendation for acoustic echo control equipment has
been prepared and is given in an annex to this Question,

1. What are the desirable characteristics of equipment used to control
acoustic echoes in the applications listed above and what
characteristics should be recommended?

2. What tests should be recommended to determine compliance with these
characteristics?

3. How will speech sampled and coded using techniques which differ from
those given in Recommendation G.711 affect the design of acoustic echo
control equipment and what should be recommended to take proper account
of this?

4. What interactions will there be between acoustic echo control
equipment and network echo cancellers which conform to Recommendation
G.165 and/or echo cancellers used in the ISDN digital subscriber line,
and what should be recommended to keep any undesirable interactions
within acceptable limits?

Notes

1. Account should be taken of the work in Study Group XII on subjective
testing and acoustic characteristics of the teleconference rooms.

2. Account should be taken of the work in Study Group XVIII on ISDN and
general network issues.

3. Account should be taken of the studies of network echo control
equipment carried out under Question 7/XV.

ANNEX

(to Question 8/XV)

Draft Recommendation G.AEC

ACOUSTIC ECHO CONTROLLERS FOR TELECONFERENCING APPLICATIONS

Recoup

2.

In Annex 1

3.5

4.4

5.

Fig.

Test

7.

Annex 1