"My experience has been hearing just a few notes that are similar to my phone's ring, my brain will fill in the rest," said David Laramie, a doctoral student at the Los Angeles campus of the California School of Professional Psychology, who is writing his dissertation about the effect of cellphones on behavior.

He plans to send questionnaires this summer to learn when and how often phantom rings happen and who is most likely to experience them. A few notes in the background of a television commercial can fool him, he said. Other times the culprit will be the sound effects in a song on the radio. "Another place I hear it is running water, so I sometimes hear it while I'm shaving," Mr. Laramie said.