Abstract: A high performance hearing protection or communications earcup and seal is disclosed that takes advantage of the facts that a characteristic acoustic impedance mismatch at a boundary will reflect a large portion of impinging energy rather than absorb it, and the "pumping" action on an elastomeric boundary from cyclic acoustic pressure can be damped by placing damping materials adjacent to that boundary. The preferred embodiment of the hearing protection earcup seal of the instant invention interleaves damping materials between the plurality of concentric ring structures of the instant invention and places thinned edges on individual concentric ring structures to enhance seal conformation with obstacles such as eyeglass temple pieces. An elastomeric semi-annular tensile plate supports the concentric ring structures of the instant invention. Both the earcup and earcup seal of the instant invention are readily manufacturable with conventional tooling.

Abstract: A multi-technology acoustic energy barrier and absorber is disclosed that employs the teaching of U.S. Pat. No. 5,400,296 for a matrix material with at least two species of particles with differing characteristic acoustic impedances, in combination with the teaching of U.S. patent Pending Ser. No., 08/780,271, for an "Acoustic Absorption or Damping Material with Integral Viscous Damping," and with the principles underlying constrained-layer dampers.

Abstract: Acoustic absorption or vibration damping materials are produced by mixing at least two species of particles into a restricted amount of matrix material in order to produce an acoustic absorption or vibration damping material with tortuous passageways throughout the material. The tortuous passageways of the instant invention serve to: a) reduce acoustic reflectivity at the surface, b) provide channels within which the interfacing medium such as air can interact viscously, c) increase the surface area between interfacing media and, d) improve structural stiffness by adding thickness without adding weight. Particle species within the matrix material are differentiated by their acoustic impedances. A particle species of particular interest is crumb tire rubber from used tires. This material is inexpensive and its use in this application has the societal advantage of making productive use of a material that is currently polluting the environment.

Abstract: Acoustic absorption and vibration damping materials are produced by mixing electrically conductive particles or strands into a piezoelectric matrix material. The electrically conductive particles or strands act as small localized electrical short-circuits within the matrix material and effectively dissipate the electric charges produced by piezoelectric effect from the pressure of acoustic or vibrational energy as heat. All energy thus converted into heat is subtracted from the original acoustic or vibrational energy, resulting in acoustic absorption and/or vibration damping.

Abstract: A means of enhancing the acoustic attenuation and vibration damping of a material by embedding high characteristic acoustic impedance particles, low characteristic acoustic impedance particles, or both high and low characteristic acoustic impedance particles within the matrix of the material is disclosed. The mass of the resultant material may be very low while retaining excellent acoustic attenuation, vibration damping, and structural characteristics. When particles with mismatched characteristic acoustic impedances are embedded within the matrix of a material that can support shearing loads, propagating acoustic energy that encounters the particles of the instant invention is partially reflected in random directions. That is, the propagating energy is diffused. As the propagation vectors and modes of acoustic energy are effectively randomized, the probability of localized energy absorption and damping is increased.