The business of selling ring tones — or musical jingles that can personalize a mobile phone — is proving to be more than just a lot of hot air.

The market has already topped $1 billion globally and has been all the rage in Europe and Asia for several years. Sales in the United States are igniting, with young people leading the charge.

Thousands of customers have already downloaded ring tones mimicking flatulence noises since Modtones began offering them three weeks ago.

“It’s pretty impressive, considering there was no promotion and no press,” she said. “You stick it underneath someone’s chair and dial your own number and it’s a remote-controlled whoopie cushion.”

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