The AVModalityPropertyChanged event is not triggered when the value of the AVModalityAudioNetworkQuality property or the AVModalityAudioDeviceQuality property changes inMicrosoft Lync 2010 SDK.
To resolve this issue, install the following cumulative update:
2496325 Description of the cumulative update package for Lync 2010: April 2011
For more information about the AVModalityPropertyChanged event, visit the following Microsoft website:
For more information about the AVModalityAudioNetworkQuality property and the AVModalityAudioDeviceQuality property, visit the following Microsoft website:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.