CS6422
CS6422
6. GLOSSARY
Echo
A signal that returns to its source after some delay.
Network Echo
Echo resulting from signal reflection due to an impedance mismatch in a 2-to-4 wire converter (hybrid).
Acoustic Echo
Echo created by signal propagation in a room from a speaker to a microphone.
Reverberation
Local information that bounces around the room before it reaches the microphone. An example of
reverberation is when your back is to the speakerphone, and your voice bounces off the wall before it
reaches the microphone.
Near-End
The location with the acoustic interface (speaker and microphone).
Far-End
The location connected to the network interface.
Transmit Path
The signal path from Near-End input to Far-End output.
Receive Path
The signal path from Far-End input to Near-End output.
Full-Duplex
The state when both Transmit and Receive paths are simultaneously active.
Half-Duplex
The state when either Transmit or Receive path is active.
Supplementary Echo Suppression
Dynamic attenuation placed in the opposite path of the active path to mask residual echo. For example,
if the receive path is active, the transmit path is attenuated. When both paths are simultaneously active,
the suppression attenuation is removed. See Section 4.1.4, “Suppression” for more details.
Howling
In full-duplex operation, both the microphone and speaker are active at the same time, which, in
conjunction with the reflection off the hybrid, creates a closed loop. The signal coupling between the
speaker and the microphone can cause feedback oscillation or howling. This happens when the
coupling between the speaker and microphone is strong enough to increase the system's closed loop
gain above unity.
Acoustic Coupling
The strength of the output signal from the speaker that is received at the microphone input.
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