Where we are located, you could always just slightly hear a local radio station in the backgroud when we were on a standard phone. With the AudioCodes MP-114 hooked up and everything digital, it has become VERY loud, any suggestions?
Sounds as though your cabling may be unshielded and you are getting crossover signal from the radio station. Basically the cable is acting like a big antenae.
Are there any areas where the cable is significantly exposed to radio signals? Maybe a segment that is run outside on the roof or along a window? If so can you reroute it, replace it with shielded cable or maybe put in some filters?
Have you noticed any distortion or interferance in your normal network traffic?
It does sound like it may be the phone lines then.
You may want to contact the phone company since this problem degrades the service for which you are paying. They may provide the filters and installation free of charge. At the very least they should be able to direct you to filters that will work with their systems.
Sorry I don't have a brand name for you but you can get a variety of filters that phug into the back of the phones or PBXs at Radio Shack and other electronic stores.