The red Focusrite Scarlett box controls the output to the actual mock scanner speakers. You want the MRI noise to come through those speakers, so you may need to change Audacity's preferences to output there.
To change the preferences:
Go to Edit>Preferences
|Go to Edit>Preferences|
|Change the Playback Device to "Line Out (Scarlett 6i6 USB), click OK.|
|At the beginning of your session, simply open the MRI 3T Scanner Noise (in Audacity), and hit play. Use the volume control on the red Focusrite box to turn the noise "on" or "off" throughout the session.|
Reviewed 10/2/17 - Cox