Barge In issue

PBX Firmware:

When I use the barge in feature 888 and the trunk code 01# I’m listing to dead air until the channel is used. (this is what I need) but after the call ends I get a 8k tone until the next call is placed. The only way I can stop the tone is to barge into an other active call and then go back to trunk 01. After resetting I get no tone until the next call ends.
What I would like to never to hear the tone.
Any ideas?