Two US scientists are working on ways to use sound to chill food thereby ending current reliance on harmful greenhouse gases for refrigeration.

Matt Poese and Steve Garratt of the Applied Research Laboratory at Penn State University are working to develop a small chiller cabinet that would be used to keep ice cream cool.

Using the fact that sound waves travel by compressing and expanding the gas they are generated in, Poese and Garratt are using sounds of 173 decibels to cool and heat metal plates in the path of the sound wave. A refrigerator can then be created by attaching heat exchangers to the end of the stack of plates that are put in the correct place inside a tube in which the sound wave is travelling.

The sounds are so loud that they are dangerous to humans - sounds of 165 decibels would make a person's hair catch fire from the heat caused by the friction that is created when air is undergoing such intense compression and expansion. In Poese and Garratt's fridge, however, the sounds are generated inside a pressurised gas locked inside the cooling system and cannot escape even if the fridge cracks open.

The research, which is being sponsored by ice cream makers Ben & Jerry's and Unilever, could also make fridges more reliable because a thermoacoustic fridge has fewer moving parts, reports BBC Online.