Abstract: A method of manufacturing acoustic panels comprising the steps of pouring a solidifiable liquid into a container, placing a porous layer of material onto the solidifiable liquid, solidifying the solidifiable liquid into a rigid layer, and removing the rigid layer and the porous layer from the container. The container has at least one form member extending from the bottom of the container upwardly. This form member extends upwardly into the porous layer. The solidifiable liquid is a slurry of cement. The container and the form member are magnetically attractive. The form member has a generally tapered cylindrical shape and rounded edges. The porous layer is a fibrous material.

Abstract: The present invention is an acoustic panel having a porous layer and a generally rigid layer affixed to each other. The generally rigid layer includes at least one passageway opening on one side of the rigid layer and extending through the rigid layer to the porous layer. The porous layer is a fibrous material. The rigid layer is a concrete-type material, such as vermiculite-cement plaster. This acoustic panel further comprises a generally rigid planar surface positioned adjacent to the porous layer. This generally rigid planar surface can comprise an insulating layer affixed to the other side of the porous layer and a structural layer fastened to the insulating layer. The insulating layer is a polyurethane foam board. The structural layer is a particle board.

Abstract: The invention sorts small particles by subjecting them to a charging and motivating field produced by a single positively charged electrode. The magnitude of the charge placed on the particle passing the electrode is a function of the observed particle parameters. Once the particle has been deflected in accordance with its observed parameter, the particle may be collected for further study.