= Tutorial 6: Computing a noise covariance matrix =
The source reconstruction process requires an estimation of the noise level in the recordings. This tutorial shows to compute the noise covariance matrix for the two averaged files we have in database.

 * Select protocol TutorialCTF, switch to the ''Functional data (sorted by subjects) ''view.
 * To estimate the noise covariance matrix, we need to use only the real recordings, and not the variance of the average (second recordings file of each condition). So select them at the same time (using the SHIFT or CTRL key) : StimRightThumb/ERP and StimLeftThumb/ERP. Then right-click on one of them.<<BR>><<BR>> {{attachment:noiseCovMenu.gif}}
 * The Noise covariance menu includes:
  * '''Import from file''': Uses a matrix that was computed previously using the MNE software.
  * '''Import from Matlab''': Import from any [nChannels, nChannels] matrix in Matlab workspace.
  * '''Compute from recordings''': Use the selected recordings to estimate the noise covariance.
 * Select "Compute from recordings":<<BR>><<BR>> {{attachment:noiseCovOptions.gif}}

=== Use a noise cov. matrix from another dataset ===
Divide