In 2006, a high-pitched ringtone known as the "Mosquito" ringtone was field-tested. While children could hear the sound loud and clear, most adults failed to detect it.

The ringtone was originally developed in England to deter teenagers from loitering near stores. It gained popularity among American kids as a school-friendly ringtone that allowed them to communicate discreetly. “They never know when people are calling you on your cell,” one child remarked.

Hearing specialists explained that high frequencies, often above 8,000 to 10,000 hertz, are the first to deteriorate with age, making the sound inaudible to most adults.

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