You didn't provide much to go on, but my guess is that the beeping sound is an alert signal reminding officers that the channel in question is closed to general use and only available to officers on a specific call where there is currently a high risk operation active. It could also be something as simple as the scanner is listening to a trunking channel in conventional mode so you're hearing the system's "housekeeping" signals.
If you can provide more specifics on where and when you're hearing that "beeping noise" (e.g. "The Mayberry PD Dispatch Channel" or "Talkgroup 93275 on the Podunk ID Trunking Radio System") folks around here can probably give you a pretty good answer to what's going on.
The "garbled sound" may be one or more of the agency's encrypted transmissions. This may be confirmed if you can provide details on which channels those are as well. Assuming that you're listening to this system (http://www.radioreference.com/apps/db/?sid=257), those with a Mode of "E" are the encrypted channels.
On very windy days where the feed is (East mountains) the tower gets to shaking and the Yagi or directional antenna gets to moving around and the feed radio will lose the control channel and beep when it finds it again. Also it will get poor signal from time to time and the radio traffic will sound like crap. I have battled this problem for a year now and have worked most the problems out but when its really windy out here its not going to sound great.
Still trying to get settled into the new house. I need to get a longer coax cable for the antenna and get the antenna set up on the roof. I have been doing some testing and I think it will work just need to get some things and get on the roof and for some coax. I hope in the next few weeks