The WM/WMADRCAverageReference attribute contains the average volume level of the file as encoded.
There are four attributes used by Windows Media Player for dynamic range control: WM/WMADRCAverageReference, WM/WMADRCPeakReference, WM/WMADRCAverageTarget, and WM/WMADRCPeakTarget. All of these values are set by the writer based on information from the codec when writing streams with the Windows Media Audio 9 codec or Windows Media Audio 9 Professional codec. The average values are set to the average volume level of the stream, and the peak values are set to the maximum volume level in the stream. The reference values are read-only. The target values are set by Windows Media Player when the file is being played to record the dynamic range control preferences of the user.