Advice

The Adaptive Filter is useful in situations where a faint echo is still being heard on the far end after adjustments have been made to the affected mic gains and to the AEC reference signal.  

The "Hold If Mic Level Below" threshold, which is defaulted to -100 dB, will keep the AEC active even when no one is speaking, allowing for smooth operation.  In most cases this should suffice, but in some situations if the microphone level is not low enough or muted, it can cause a faint echo occur.  In such an instant, it would be best to increase the Hold level from it's default until the echo goes away.

If far end audio being fed into reference pin has elevated background noise, this can cause issues with AEC adaptation.  The "Hold If Ref Level Below" threshold can also be used to troubleshoot these issues.  This can be done by adjusting the level from the default -100 dB.