Why people seem to be hearing phantom rings more often now is another question. The answers range from the paranoid to the vast exposure to cellphones in people's lives — there were 207 million wireless subscribers nationwide at the end of 2005, a nearly sevenfold increase in just a decade, according to the Cellular Telecommunications and Internet Association.

On blogs, some cellphone users wonder if an ominous agenda is at work when a phantom ring is triggered by a television or radio broadcast. A writer posting as Koan on forumgarden.com said that at first, songs played on the radio triggered a phantom ring. "Thing is, the high-pitched sounds, although a lot fainter, are still present during announcements now," Koan wrote. "What is this? Is it subliminal advertising ... or something else?"

Peter Arnell, the chief creative officer of the Arnell Group in New York and a major force in the marketing business, said that theory might not be far off the mark. While he said he has never been asked by a client to include sounds in an advertisement that would mimic a ringing cellphone, he thinks the increasing use of high-pitched, electronic tones is very much by design.

"People are using a sound trigger to control emotions," Mr. Arnell said. "The most controlling device in our life right now is a cellphone."

He suggested that a sound trick that sent confused listeners hunting for their cellphones might be especially effective for ads ending with a call to action. (An example is a directive to "Call this toll-free number now!")

"Hollywood has always known how to use sound to control emotions, right?" Mr. Arnell continued. "But this is newer to advertising. Sound effects have become the big deal on Madison Avenue."