I had my scanner programmed at Radio Shack(that is where this police/fire scanner comes from) and it has this annoying beeping sound when a frequency comes in. It also has this hissing sound.
I had this problem couple years ago and some at a Radio Shack knew what to do and corrected it. Now I went to several Radio Shack and nobody know how to operate a scanner.
It has to be something minor, but I've been trying and cannot solve the problem without locking out my primary city fire/police frequencies. It is mainly only on that channel that this beeping comes in during a transmission.