Narrative:

High pitch loud tones are occasionally over the console through headset, north radar position. On south radar, these tones come through speaker.

Google
 

Original NASA ASRS Text

Title: SAV CTLR RPTS TONES FROM UNKNOWN SOURCE ARE HEARD THROUGH CTLR HEADSET AND SECTOR SPEAKERS, WHEN NOT MANNED.

Narrative: HIGH PITCH LOUD TONES ARE OCCASIONALLY OVER THE CONSOLE THROUGH HEADSET, N RADAR POS. ON S RADAR, THESE TONES COME THROUGH SPEAKER.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.