Solved.
From ButtonRecord, set the WaveWriter format to mono, then change the WaveIn_DataAvailable as follow:
From ButtonRecord, set the WaveWriter format to mono, then change the WaveIn_DataAvailable as follow:
Private Sub WaveIn_DataAvailable(ByVal sender As System.Object, ByVal e As NAudio.Wave.WaveInEventArgs) Handles WaveIn.DataAvailable
For i = 0 To e.BytesRecorded / 2 - 1
e.Buffer(i) = e.Buffer(2 * i) ' keep the left channel
' or, e.Buffer(i)=e.Buffer(2*i+1), to keep the right channel
Next
WaveWriter.Write(e.Buffer, 0, e.BytesRecorded / 2)
End Sub