Abstract: An active acoustics management system for the loudspeaker back-enclosure, including a first loudspeaker having a front side and a back side connected by side walls, the front facing in a first direction, is presented. An enclosure surrounds a portion of the first loudspeaker, such that the enclosure is open about the front side of the first loudspeaker and is closed about the side walls and the back side of the loudspeaker. A second loudspeaker is disposed within the enclosure behind the first loudspeaker, the second loudspeaker being oriented to output waveforms in the first direction, wherein the second loudspeaker is adapted to output waveforms in the first direction thereby to cancel at least some waveforms emanating from the back side of the first loudspeaker, using active control strategies.

Abstract: An acoustic metamaterial (AMM) passive impedance matching technique to enhance the acoustic performance of porous/poro-elastic sound absorbing materials is disclosed. An AMM passive matching device is implemented by achieving negative refractive index with double negative parameters, i.e., negative effective mass density and effective bulk modulus scheme, using various acoustic elements. The AMM technique consists of meta material architecture of acoustic inductive open tubes positioned strategically around the outside surfaces of the porous media and perforated screens inserted inside porous media to generate complex acoustic impedance load of the porous media; the inductance defined by a predetermined lengths of the open tubes. The device includes open tubes extending from the porous media to the outside ambient medium generating the desired reactive load over the broadband frequency region of the complex acoustic impedance of the porous media.

Abstract: An active acoustics management system for the loudspeaker back-enclosure, including a first loudspeaker having a front side and a back side connected by side walls, the front facing in a first direction, is presented. An enclosure surrounds a portion of the first loudspeaker, such that the enclosure is open about the front side of the first loudspeaker and is closed about the side walls and the back side of the loudspeaker. A second loudspeaker is disposed within the enclosure behind the first loudspeaker, the second loudspeaker being oriented to output waveforms in the first direction, wherein the second loudspeaker is adapted to output waveforms in the first direction thereby to cancel at least some waveforms emanating from the back side of the first loudspeaker, using active control strategies.

Abstract: An acoustic metamaterial (AMM) passive impedance matching device for headphone-type devices for matching the complex acoustic impedance load of a human ear to enhance acoustic performance of a headphone is disclosed. The device includes shunt compliance chambers stacked concentrically relative to one another from an upper end to a lower end. Each of the shunt compliance chambers includes side connecting inductive channels positioned annularly around a circumference of at least one of the shunt compliance chambers. The shunt compliance chambers define a predetermined volume of air. The inductive channels connect the shunt compliance chambers to the main headphone volume, generating an acoustic resistance and reactive impedance that matches the complex acoustic impedance load of the human ear canal. The AMM device also includes an inductive channel, as a design parameter, extending from the main headphone volume to the ambient air serving as an additional resistive and reactive load.

Abstract: An active acoustics management system for the loudspeaker back-enclosure, including a first loudspeaker having a front side and a back side connected by side walls, the front facing in a first direction, is presented. An enclosure surrounds a portion of the first loudspeaker, such that the enclosure is open about the front side of the first loudspeaker and is closed about the side walls and the back side of the loudspeaker. A second loudspeaker is disposed within the enclosure behind the first loudspeaker, the second loudspeaker being oriented to output waveforms in the first direction, wherein the second loudspeaker is adapted to output waveforms in the first direction thereby to cancel at least some waveforms emanating from the back side of the first loudspeaker, using active control strategies.

Abstract: An active acoustics management system for the loudspeaker back-enclosure, including a first loudspeaker having a front side and a back side connected by side walls, the front facing in a first direction, is presented. An enclosure surrounds a portion of the first loudspeaker, such that the enclosure is open about the front side of the first loudspeaker and is closed about the side walls and the back side of the loudspeaker. A second loudspeaker is disposed within the enclosure behind the first loudspeaker, the second loudspeaker being oriented to output waveforms in the first direction, wherein the second loudspeaker is adapted to output waveforms in the first direction thereby to cancel at least some waveforms emanating from the back side of the first loudspeaker, using active control strategies.

Abstract: A meta acoustic horn (MAHI) device for passive amplification of sound is described. The MAH audio amplifier device employs a deep sub-wavelength acoustic meta material horn design with high refraction index, which provides amplification of the sound over large audio frequency range. An array of sub-wavelength, zig-zag channels, contained in a horn-like micro channel is devised, to achieve amplification of sound. This is accomplished by varying the width and port opening of the channel in a fixed ratio, called MAH ratio, opening extending in a same, common, or substantially common direction. The sound emanating from a speaker enters the opening of the MAH channel and comes out amplified at the output port. The sound from the speaker is in all transmitted frequencies of, for example, a musical recording or the like. All frequencies of the original sound thereof are substantially propagated through the MAH channel, and are amplified.

Abstract: A method and apparatus comprising a composite panel and a number of structures to reduce noise radiation from the composite panel. The composite panel has a first face sheet, a second face sheet, and a core located between the first face sheet and the second face sheet. The number of structures is associated with the first face sheet. The number of structures has a mass with a configuration to reduce a speed of waves propagating in the composite panel such that noise radiating from the composite panel is reduced.

Abstract: A method and apparatus comprising a composite panel and a number of structures to reduce noise radiation from the composite panel. The composite panel has a first face sheet, a second face sheet, and a core located between the first face sheet and the second face sheet. The number of structures is associated with the first face sheet. The number of structures has a mass with a configuration to reduce a speed of waves propagating in the composite panel such that noise radiating from the composite panel is reduced.

Abstract: A method and apparatus comprising a composite panel and a number of structures to reduce noise radiation from the composite panel. The composite panel has a first face sheet, a second face sheet, and a core located between the first face sheet and the second face sheet. The number of structures is associated with the first face sheet. The number of structures has a mass with a configuration to reduce a speed of waves propagating in the composite panel such that noise radiating from the composite panel is reduced.

Abstract: A method and apparatus for reducing sound. A layer of material has holes extending from a first side of the layer of material to a second side of the layer of material. The holes are configured to provide a desired level of acoustic resistance to sound traveling through the layer of material. The layer of material is configured to be mounted to a platform.

Abstract: A method and apparatus comprising a composite panel and a number of structures to reduce noise radiation from the composite panel. The composite panel has a first face sheet, a second face sheet, and a core located between the first face sheet and the second face sheet. The number of structures is associated with the first face sheet. The number of structures has a mass with a configuration to reduce a speed of waves propagating in the composite panel such that noise radiating from the composite panel is reduced.

Abstract: A method and apparatus are present for reducing noise. The apparatus comprises a core and a face sheet. The core is configured to reduce a speed of shear waves traveling through the core. The face sheet is located over a first surface of the core and is configured to reduce a speed of bending waves traveling through the face sheet. A second surface of the core is configured for attachment to a surface of a structure.

Abstract: An apparatus comprises a core having a first surface configured for attachment to a surface of a structure, a face sheet located over a second surface of the core, a number of cavities within an interior of the core, and a number of ports for the number of cavities. The number of ports provides communication between the number of cavities within the interior of the core and the exterior of the core. The number of cavities and the number of ports are configured to reduce noise traveling through the core.

Abstract: A passive piezoelectric damping system dissipates mechanical energy propagating through a structure by tuning a shunt inductance to a non-resonant mode of the structure. The damping system includes a piezoelectric element coupled to the structure, where the piezoelectric element converts the mechanical energy into electrical energy. The electrical energy has a reactive component. The damping system further includes a shunt circuit connected to the piezoelectric element for balancing the reactive component of the electrical energy with a shunt inductance. The shunt inductance is tuned to a non-resonant mode of the structure to reduce airborne noise transmission through the structure.

Abstract: A passive piezoelectric damping system dissipates mechanical energy propagating through a structure by tuning a shunt inductance to a non-resonant mode of the structure. The damping system includes a piezoelectric element coupled to the structure, where the piezoelectric element converts the mechanical energy into electrical energy. The electrical energy has a reactive component. The damping system further includes a shunt circuit connected to the piezoelectric element for balancing the reactive component of the electrical energy with a shunt inductance. The shunt inductance is tuned to a non-resonant mode of the structure to reduce airborne noise transmission through the structure.