Abstract: An acoustic device has first and second conduits such that the first conduit has an inlet and an outlet, and the second conduit encloses a material that is different from the material in the first conduit, or encloses the same material as that in the first conduit but at a different pressure. The first and second conduits share a common wall that is made up of a flexible membrane that allows acoustic signals in the first and second conduits to be acoustically coupled together, thereby allowing acoustic signals in the first conduit to be altered to suppress, enhance, or change certain aspects of the acoustic signal without the use of electronics.

Abstract: A multiple phase stethoscope has a chest piece with a plurality of diaphragms and an equal plurality of sound compartments. Sound is carried from each of these compartments through a separate lumen, the plurality of lumens making up a tube assembly. The lumens are at least partially separated from each other by a flexible membrane which serves as a transducer to convert acoustic energy into mechanical motion, thus allowing the sound in the lumens to be combined. One of the lumens is open to the atmosphere through ear pieces, while the other lumen is sealed with a material and/or pressure different from the ambient environment. The geometry of the diaphragms, the compartments, and the lumens; the materials used for the flexible membrane in the lumens; and the pressure of the material in the lumens are all selected to enhance and/or attenuate at least a part of a frequency spectrum of the sounds.