You may want to check that someone doesn't have their radio set to Speaker. If it is, anything transmitted on that net will come over the radio's speaker, and you'll hear it if you're in a certain radius of the individual. You can know for sure, if you get close to the sound, and if you open broadcast on that specific net, you'll hear loud feedback from their speaker. Then you can tell them to set it to headphones, and if that's your problem, all will be well.