Fix for issue 678: Amplitude issue in BWE during bitrate switching

[x] With these changes, the high frequency burst observed at ~2.8s is resolved.

EVS 26.444 BE test passes.
pytests results: 597 failed, 381 skipped

MLD scores:
Original inputs:
MLD > 10: 56
MLD > 5 : 120
MLD < 5 : 421

+10dB inputs:
MLD > 10: 184
MLD > 5 : 194
MLD < 5 : 219

-10dB inputs:
MLD > 10: 19
MLD > 5 : 57
MLD < 5 : 521