B737-500 FLT CREW; WHILE TAXIING FOR DEP; INDICATES THAT THE ATC VOICE COMMUNICATIONS VOLUME IS VERY LOW AND HARD TO UNDERSTAND AT ORD.

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ROUTINELY ORD FREQS FROM GND TO APCH/DEP ARE DIFFICULT TO HEAR DUE TO LOW CTLR VOLUME. ALL ACFT ARE AT ONE VOLUME LEVEL WHILE ALL CTLRS ARE AT ANOTHER MUCH LOWER VOLUME LEVEL. THIS IS ONGOING FOR SOME TIME AND NOTED BY MANY CREW MEMBERS. A SAFETY ISSUE EXISTS AS IT REQUIRES CONTINUOUS CYCLING OF AUDIO PANEL VOLUME TO HEAR AND UNDERSTAND CTLRS. NUMEROUS ON FREQ REQUESTS TO JOIN THE VOLUME LEVEL OF THE PLTS ARE ONLY TEMPORARILY HONORED. BEST GUESS IS THAT BOOM MIKES ARE FAR TOO FAR FROM MOUTH. HAVE NOT EXPERIENCED THIS AT OTHER FACILITIES. IT IS AN ISSUE THAT NEEDS TO BE ADDRESSED.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR INDICATED THAT HE HAS TO CONSTANTLY ADJUST THE VOLUME CTL WHILE COMMUNICATING WITH ORD CTLRS. HE INDICATED THAT THIS INVOLVES ALL THE CTLRS TO INCLUDE GND; APCH; AND TWR. THE RPTR OPERATES FROM MANY DIFFERENT ARPTS AND IT SEEMS THAT ORD IS THE ONLY PLACE THAT HAS A VOLUME PROBLEM. A QUERY OF OTHER PLTS INDICATED THEY HAVE THE SAME DIFFICULTY WITH VOLUME FROM ORD CTLRS. THE CONSTANT ADJUSTMENT OF THE VOLUME CTL IN THE ACFT TO BE ABLE TO HEAR THE CLRNC HAS BECOME A SAFETY ISSUE TO THE RPTR. THE RPTR SUSPECTS THAT THE CTLRS LET THEIR BOOM MIKES GET TOO FAR FROM THEIR LIPS AND THIS CAUSES THE VOLUME TO BE LESS. RPTR STATED QUERY OF CTLRS REGARDING THE PROBLEM WILL FIX THE SITUATION FOR A SHORT PERIOD; HOWEVER HE INDICATED THAT IT RETURNS VERY QUICKLY.