Abstract: An underwater communicator comprising a transmitter for transmitting acoustical energy between mediums having differing impedance. The transmitter includes first and second ends. The first end is exposed to a first medium while the second end is exposed to a second medium. In the preferred embodiment, the transmitter is formed from a material having a substantially identical impedance to the second medium. An acoustical lens is positioned adjacent the first end of the transmitter. The acoustical lens has a substantially planar front face and a substantially concave shaped rear face. The acoustical lens includes a plurality of spaced vertically extending plates. The vertically extending plates form a substantially right angle with the front face of the acoustical lens. A plurality of spaced plates intersect the vertically extending plates and form an acute angle with the front face of the acoustical lens, thereby forming a plurality of inclined passageways.

Abstract: A method of making a solar collector panel comprises the steps of applying a quantity of solvent to one face of a synthetic foam sheet to form a pattern of solvent stripes on said face, allowing the applied solvent to etch a pattern of grooves having highly irregular surfaces, painting the surfaces of the grooves exposed by the action of the solvent with light-absorbing coloring matter, and securing a light-transmitting cover sheet to the remaining portions of said face. The cover sheet, when secured, conforms to the shape of the face prior to the solvent application step, whereby the grooves and the cover sheet together form channels for the flow of a heat transfer fluid such as water or air.