Minnesota Mining and Manufacturing Company

3m Innovative Properties Company

Gary N Harvieux

Leland Ray Whitney

Charles A Marttila

Ronald W Gerdes

Thomas J Scanlan

Joseph G Mandell

David W Schilling

Michael W Dolezal

Enclosure 1 constructed of panels 20 which can be joined by tongue and groove or press fit spline 46 and groove 26 technique. Acoustic shielding is achieved by properly selected materials of construction, e.g. syntactic, cellular composites. The doorway 10 of the enclosure is closed by a door 210 penetrated only by a guide 175. The latch mechanism 170 and 340 seals the door against the door jamb 185 by means of cam rollers 316 which engage indentations 189 (which may have specialized cam surfaces or inclined surfaces) along the door frame. The latch mechanism can be actuated from either side of the door by mechanical means engaging the guide.

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A method of using a material as an acoustical barrier in an ambient medium. The material comprises microbubbles having average outer diameters of 5 to 150 microns, bound together at their contact points. The material is characterized by either a porosity of 20 to 60 percent, or by voids between the microbubbles which have characteristic diameter within an order of magnitude of the viscous skin depth of the ambient medium, as calculated at 1 kHz; an air flow resistivity of 0.5.times.10.sup.4 to 4.times.10.sup.7 mks rayls/meter, and an attenuation of sound comparable to mass law performance. The microbubbles can be sintered into direct contact with each other, or one of many types of binder material can be used to support the microbubbles within a composite material. The method may be practiced in an acoustical system comprising a sound source and the material, such as by placing a muffler comprising the material substantially in a direct path of a fluid; and also in applications requiring high specific stiffness and flexural strength.

Use of materials comprising microbubbles as acoustical barriers

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Woodbury, MN, United States of America

Gary N Harvieux