People don't realise they are 'broadcasting' because they subconciously raise their speaking voice in order to 'hear' themselves as they are speaking. In conversation, this is automatic, and we all moderate our voices to nromal level. On a land-line telephone, we are usually undoors, and background noise is minimal. Mobiles, used in the open air, with a lethal combination of bad singaling giving faint feedback, combined with external noise sources gives the famous 'shouted' conversations you hear everywhere. All mobile users should be forced to watch Dom Joly's 'Mobile Man' on 'Trigger Happy TV' - it would make them think twice before doing it again!