Any Unknown or Unlisted Aircraft Manufacturer
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2.5
Troubleshooting; Distraction; Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
ATC Equipment / Nav Facility / Buildings; Procedure; Human Factors
I was working the South High sector (at the R4 scope) which takes Midway traffic on two arrivals; sequences; descends and hands off to Chicago Approach. The radar scope next to mine (R3) was out of service due to a headphone jack not working.  One of our technicians was working on the jack.  She went into the back room to test something.  Without warning; a deafening squelch/tone was heard not only throughout the TRACON over one of the speakers; but also on the frequency I was using and directly into my ear through my headset.  I immediately removed my ear piece and put the frequency on speaker.  The technician came back into the TRACON and I informed her of what had just happened.  Her response was; 'Oh; I didn't know you had that keyed up.'  I left the traffic on speaker until the maintenance was completed in case it happened again.  After it was completed; I put my ear piece in the other ear because there was still a ringing sound on one side. I recommend tech[nicians] ask which frequencies are keyed up and being used before sending loud; ear damaging squelches and tones through them. It is damaging to hearing and disruptive to the controller working traffic.
SBN Controller reports of an audio jack that is out of service.  Maintenance works on the jack and while doing so a loud squeal emits from the frequency into the Controller's ear.