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"The third most powerful sound is just over 10 years old, and yet it had such a profound effect on our volunteers that as soon as they hear it, they remove their headsets and check their bags for their vibrating cell phone. When we switch our phone into silent mode, we think it cannot be heard. But the vibration has its own sound, and almost immediately the test subjects stopped whatever they were doing to attend to their phones. It’s hardly surprising that the Blackberry has been dubbed a CrackBerry—even President Obama is hooked."