Charge phones with your voice

Yesterday I stumbled upon the news that Sang-Woo Kim of Sungkyunkwan University found a way to charge your cell phone with converting noise to electricity. When I come upon such stories, we pass it around the office, we have a good laugh and get done with it. 

For starters the device that converts sound waves to electricity you must need a "microphone". The problem is that it generates so little electricity that it's not useful for anything but transmitting small amounts of data.
Then comes the source claiming that at the current state of their project they are producing 50 Milli volts from 100 decibels of noise, but they promise to do better in the future. Do you know how much 100 decibels amount to? Let's just say that a gasoline engine chainsaw produces noise in the range of 90-112 decibels. Yes, 100dB is that loud.