Why Mobile Phones are Annoying: Jakob Nielsen comments on a study of why overheard mobile conversations are considered so annoying. The study had actors fake regular conversations (between two people) and cell phone conversations, then surveyed the bystanders to find out how annoyed they were with what happened.
…even phone conversations in a normal voice received worse scores than face-to-face conversations. The worst problem seems to be that conversations on mobile phones are more noticeable than face-to-face conversations. This seems odd, since two people talking together project twice the amount of audio as one person talking on the phone.
Unfortunately, Monk and his colleagues don’t provide the final answer; more research is called for. But the problem seems to be that people pay more attention when they hear only half a conversation. It’s apparently easier to tune out the continuous drone of a complete conversation, in which two people take turns speaking, than it is to ignore a person speaking and falling silent in turns.