Cirrus Logic AN168 - Manual (Page 22)

AN168
22 AN168REV2
sults.
6) Disconnect the signal source from NI (or sim-
ply turn it off).
7) Close the loop by setting NSdt to ‘-12dB’,
RVol to ‘0 dB’, and TVol to ‘+12 dB’.
8) Increase (or decrease) RVol until the system
just starts howling. Record this value. See Fig-
ure 16.
9) Set ACC to ‘cleared’.
10) Decrease RVol until the system just stops
howling. Record this value. See Figure 17.
11) The worst-case ERLE is the difference between
Speaker
Driver
Mic
Preamp
AO
CS6422
APO
TVol - Transmit
Volume
Air Coupling
Increase RVol until howling begins…record RVol value
0dB
-?dB
12dB
RVol - Receive
Volume
AEC
‘freeze’
30dB
+
-
-12dB
NSdt - Network
Sidetone
Adjust
+0dB
Figure 16. Acoustic ERLE Measurement -- Freeze AEC
Speaker
Driver
Mic
Preamp
AO
CS6422
APO
TVol - Transmit
Volume
Air Coupling
Clear AEC and decrease RVol until howling stops…the difference in RVol is AERLE
0dB
-?dB
12dB
RVol - Receive
Volume
AEC
‘cleared’
30dB
+
-
-12dB
NSdt - Network
Sidetone
Adjust
+0dB
Figure 17. Acoustic ERLE Measurement -- Clear AEC