Air Date: Week of August 25, 2000

Cynthia Graber reports on how sound waves can keep our food cold.

Transcript

GRABER: Refrigeration has changed the way we eat. We can store food for long periods of time and ship it around the world. But it's come with a price. The chemicals used in refrigeration, chlorofluorocarbons, deplete the protective ozone layer. CFCs are being phased out, but the chemicals that are replacing them contribute to global warming. So scientists are looking at ways to refrigerate without chemicals. One option gathering increasing attention is sound. When sound waves are pushed through gases, the gases heat up as they compress, and when the gases expand they cool down. In a refrigerating system, a tube with thin plates of plastic can transfer the heating and cooling effects produced by sound waves. One end of the tube gets hot, the other end gets cool. Cool enough to keep food from spoiling. Scientists are now trying to make these sound fridges as energy-efficient as their chemical counterparts, and protect the atmosphere, too. And that's this week's technology update. I'm Cynthia Graber.