Acoustic Metamaterials LLC

The Boeing Company

Mcdonnell Douglas Corporation

Acoustix Vr Inc.

Gopal Prasad Mathur

Michael Leslie Hand

Leanne L Lehman

Buddhadev Chakrabarti

Cliff L Chin

A method for designing and making an acoustic meta material back enclosure with a band gap tube for a loudspeaker having predefined dimensions of the enclosure is described. The method includes identifying a resonant frequency of the enclosure, as well as a baseline speaker output within a predefined range of frequencies. The method further includes defining a desired frequency range, within the predefined range of frequencies, within which it is desired to increase the speaker output, and identifying a naturally occurring band gap frequency range for the enclosure. Parameters of an acoustic meta material (AMM) band-gap tube, to be inserted into the enclosure for porting thereof, are calibrated to improve speaker output in the desired frequency range, based on the identified band gap frequency range. The enclosure is then ported using AMM band-gap tube in accordance with the calibrated parameters.

Loudspeaker system having an acoustic meta material enclosure

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. The AMM open tubes and the resistive perforated screens generate conjugate acoustic impedance that matches the complex acoustic impedance.

Meta material porous/poro-elastic sound absorbers

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.

Methods and systems for modifying acoustics of a loudspeaker back enclosure using active noise control

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.

Metamaterial acoustic impedance matching device for headphone-type devices

An acoustic meta material (AMM) spiral device for passive amplification of sound is described. The AMM amplifier device employs at least one deep sub-wavelength spiral design with high refraction index, based on an exponential spiral shape. The AMM spiral amplifier is used to focus on low frequency sound amplification and to cover broadband frequency range. Sound emanating from a speaker travels into a spiral channel until reaching the apex of the spiral. When twin spirals are used, the sound then enters a second spiral for radiating into open air.

Acoustic meta material passive spiral audio amplifier and a method to make the same

An Acoustic meta material (AMM) device for passive amplification of sound is described. The AMM amplifier device employs a deep sub-wavelength resonator design with high refraction index, which uses resonant amplification of the bass sound. An array of sub wavelength, single frequency channels are used, each resonating and amplifying at a different frequency in the bass frequency range. This is accomplished by having many different channels, each with an opening extending in a same, common, or substantially common direction. Thus, sound emanating from a speaker in a first direction continues in this direction until reaching and entering the openings of the plurality of channels. The sound from the speaker is in all transmitted frequencies of, for example, a musical recording or the like. However, only a specific frequency and/or harmonics thereof are substantially propagated through each channel.

Passive acoustic meta material audio amplifier and the method to make the same

An acoustic metamaterial passive impedance matching device for use in matching the acoustic impedance of a loudspeaker is disclosed. The device includes a baffle having an upper end and a lower end, plates stacked concentrically from the upper end to the lower end, slots positioned between the plates, a side channel extending annularly around a circumference of at least one of the plates, and a spoke interconnecting the plates. Each of the plates includes a central region including perforations. Each of the slots is positioned between two adjacent plates. The side channel defines a chamber including a height greater than the height of the plates and an interior volume enclosing a predetermined volume of air. The side channels and the perforated plates generate an acoustic impedance that matches the complex conjugate acoustic impedance of the loudspeaker to deliver maximum acoustic power. The side channels may include open ends, closed ends, or both for providing an inductive or reactive capacitance.

Metamaterial passive impedance matching device for a loudspeaker

A metamaterial loudspeaker diaphragm is disclosed. The diaphragm includes a cone structure having a periodic arrangement of two dissimilar materials, e.g., soft and hard, in an alternating periodic pattern to achieve an anisotropic structure, which results in passive amplification of the sound. The anisotropic cone structure includes a baseline cone material and a different, compatible second material. The cone includes a body having a conical cross-section, an interior side, an exterior side, and concentric circles of material alternating between a soft material and a rigid material. Circumferential grooves disposed within the concentric circles include rigid material. Concentric circles including rigid material line the interior side of the body. Substantially all the soft material of the concentric circles is disposed on the exterior side of the cone. Spokes disposed on the exterior side of the cone extend from a base toward a vertex of the cone.

Metamaterial loudspeaker diaphragm

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.

Meta acoustic horn system for audio amplification and the method to make the same

Holographic sound is recorded and reproduced by way of a single monaural recording per left and right ear recorded. This is accomplished by determining the phase shift of frequencies recorded after dividing the sound into discrete frequencies in a recording device having resonators, each resonating at a different frequency, placed in a circular arrangement and divided into discrete channels by non-resonant material. The resonators are placed in a pseudo-randomized arrangement within the recording device and the circle of resonators is in front of a microphone which records the sound monaurally. Playback is then by way of arranging speakers or transducers into micro perforated sheets which amplify the sound, the arrangement of speakers/transducers around a central point. The sound is then played back directionally based on the position where the sound originally was recorded from and the position of the particular transducer around the central point.

Acoustic holographic recording and reproduction system using meta material layers

An active acoustic meta material system with micro-perforated sheets embedded between porous layers and air gaps, around the output region in front of a speaker, perpendicular to the direction of wave propagation of the sound is disclosed. Sound input is split into two frequency ranges by an active controller, such that a higher frequency range is sent to a traditional speaker which outputs sound via a diaphragm which vibrates in response to electromagnetic signals generated based on the sound input. The sound waves in the lower frequency range are sent to piezoelectric or other type of motion-creating transducers which are mounted to an outer housing or casing containing a plurality of meta material sheets with insulative layers between each meta material sheet. The combination of meta material sheets and insulation layers are calibrated to focus and amplify the vibrational waves which are outputted by the transducers.

Growing community of inventors

Trabuco Canyon, CA, United States of America

Gopal Prasad Mathur