Jill,
Sounds like a minor feedback problem, which can easily be corrected. Go into the mic settings, lower the high EQ and raise the low EQ. Then make sure the switch on the back of the keyboard next to the mic jack is set to mic--not line. The mic level volume control on the back of the keyboard should be set to about half gain--no more. Additional gain adjustments can be made using the mic slider on the keyboard's screen. This should solve your problem. If not, try a master reset. If the problems still persists, the noise could be coming from outside sources. Try plugging the board into another outlet somewhere else and see if this helps. Also, try a different mic. Thats the best I can come up without hearing the beep in person.
Good Luck,
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)