AS3460
ALC Tuning Guide
Demo Kit Manual
• PUBLIC
UG000480
• v3-00 • 2021-Nov-08
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Figure 98:
Feedback Filter Examples
Always run the auto adaption ("Adapt" button in the simulation tab) before testing a new or modified
set of low and high leakage feedback filters. The auto adaption routine calculates several important
parameters from the measurement data and filters. Feedback filter gains for the
intermediate leakages
might be off if the auto adaption routine did not update these parameters.
There is a sub-algorithm, which manages the influence of the feedback noise cancellation on the feed
forward noise cancellation. This will only work properly once the music compensation has been tuned,
therefore it should be turned off for the initial tests of hybrid ANC. Disable "D2FBM Compensation"
and "FB Compensation" in the ALC configuration.
7.8.2
Feedback Stability
Feedback ANC should be stable in all use-cases, which means the earphone should not produce any
howling sounds, at least not when it is near or in the user's ear.
The high leakage feedback filter usually uses gains with which the earphone would start to howl if put
in the ear at a lower leakage. To counter this, first, the high leak filter should be designed with an
