Acoustic energy system

Systems described may be used in shock or motion absorbing devices, acoustic lenses, loudspeaker enclosures, etc. For a loudspeaker enclosure a sealed bag 50 of flexible plastics film contains a folded woven support 54 carrying surgical cotton layers 58 on its faces. The support 64 and layers 58 are wetted with a mixture of water and low boiling point Freons (T.M.) and sealed in the bag 50 with air. The fibres and the water serve as heat sinks interacting with the acoustic energy and interchanging heat of vaporisation and condensation with the low boiling point liquid. The volumetric compliance of an enclosure containing such bags is significantly increased especially with a spatially distributed mass of fine fibres disposed in thin layers separated by communicating channels.