Public Overridable Sub PreviewAudioVolumeGet( _
   ByVal _bsChannelID As String, _
   ByVal _nChannel As Integer, _
   ByRef _pdblAttenuationdB As Double _
) 

public virtual void PreviewAudioVolumeGet( 
   string _bsChannelID,
   int _nChannel,
   out double _pdblAttenuationdB
)

public procedure PreviewAudioVolumeGet( 
    _bsChannelID: String;
    _nChannel: Integer;
   Out  _pdblAttenuationdB: Double
); virtual; 

public: virtual void PreviewAudioVolumeGet( 
   BSTR* _bsChannelID,
   int _nChannel,
   [PARAMFLAG::Out] double _pdblAttenuationdB
) 

Parameters

_bsChannelID

_nChannel

index of a channel. Use "-1" to get a volume for all channels.

_pdblAttenuationdB

volume in dB for the selected channel.

Here is an example of how to get audio volume for all the channels:

// Volume in dB
// 0 - full volume, -100 silence
double dblVol;
m_objPreview.PreviewAudioVolumeSet("", -1, out dblVol);

Reference

MFPreviewClass Class
MFPreviewClass Members