By NICK WINGFIELD

Published: December 2, 2011

The sound of someone gabbing on a cellphone is part of the soundtrack of daily life, and most of us have learned when to be quiet — there is no talking in “quiet cars” on trains, for example.

But the etiquette of talking to a phone — more precisely, to a “virtual assistant” like Apple’s Siri, in the new iPhone 4S — has not yet evolved. And eavesdroppers are becoming annoyed.

In part, that is because conversations with machines have a robotic, unsettling quality. Then there is the matter of punctuation. If you want it, you have to say it.

“How is he doing question mark how are you doing question mark,” Jeremy Littau of Bethlehem, Pa., found himself telling his new iPhone recently as he walked down the street, dictating a text message to his wife, who was home with their newborn. The machine spoke to him in Siri’s synthesized female voice.