Source: ABC News, Eric Bland (9/16/10)
"Turning sound into a source of electrical power is possible."
"Just as speakers transform electric signals into sound, the opposite process—of turning sound into a source of electrical power—is possible," said Young Jun Park and Sang-Woo Kim, the two corresponding authors of a new article in the journal Advanced Materials.
"Sound power can be used for various novel applications, including mobile phones that can be charged during conversations and sound-insulating walls near highways that generate electricity from the sound of passing vehicles," the coauthors added. This process is based on materials known as piezoelectrics. When bent, a piezoelectric material turns that mechanical energy into electricity.
Lots of materials are piezoelectric: cane sugar, quartz and even dried bone creates an electrical charge when stressed. For decades, scientists have pumped electricity into piezoelectric materials for use in environmental sensors, speakers and other devices.
Over the last few years, however, scientists have made dramatic advances in getting electricity out of piezoelectric devices. Most of these devices, which are not yet available for consumer purchase, would generate power as a person walks, runs or, in this case, talks. The U.S. Army is even looking at partially powering some vehicles by channeling the physical impact of a bullet into a small electrical current.
The Korean scientists, however, want to harness a different kind of power source: sound waves. Their sound waves have produced a mild electrical current of about 50 millivolts, but the scientists continuing work to get a higher power output.