One-way sound transmission devices include a planar, acoustically reflective substrate having an aperture that is traversed by an elastic membrane. On one face of the substrate, two resonators are symmetrically spaced apart from the membrane at a first distance, configured to enable constructive interference between the resonators and the membrane. On the opposite face of the substrate, two other resonators are symmetrically spaced apart from the membrane at a second, greater, distance, configured to enable destructive interference between the resonators and the membrane.

An acoustic imaging metamaterial is provided for obtaining edge detection information of a tangible object. The acoustic imaging metamaterial includes a longitudinally extending phononic crystal substrate that defines a first major surface and a second major surface opposite the first major surface. A first structurally rigid grating layer is disposed adjacent the first major surface, and a second structurally rigid grating layer is disposed adjacent the second major surface. In various aspects, the first and second structurally rigid grating layers are identical in shape and dimensions, and are aligned with one another. The acoustic imaging metamaterial is configured to redirect, confine, and/or manipulate an incident acoustic wave resulting in a high contrast image used for extracting edge detection information of the tangible object. The background medium fluid of the system can be air or a fluid such as water.

Methods and systems for estimating diffraction effects during sound propagation in a scene, which include generating, for each distance value from distance values, a subpath between a first point of the scene and a second point of the scene passing through a third point of the scene which is at a distance from a path between the first point and the second point equal to the distance value. Furthermore, for each generated subpath, a transmission value related to a degree of occlusion of the subpath by objects in the scene is determined. Also, a diffraction amplitude response is determined using a first transmission value determined for a first subpath generated for a first distance value from the distance values and a second transmission value determined for a second subpath generated for a second distance value from the distance values.

Methods and systems for estimating diffraction effects during sound propagation in a scene, which include generating, for each distance value from distance values, a subpath between a first point of the scene and a second point of the scene passing through a third point of the scene which is at a distance from a path between the first point and the second point equal to the distance value. Furthermore, for each generated subpath, a transmission value related to a degree of occlusion of the subpath by objects in the scene is determined. Also, a diffraction amplitude response is determined using a first transmission value determined for a first subpath generated for a first distance value from the distance values and a second transmission value determined for a second subpath generated for a second distance value from the distance values.

A sound absorbing unit includes: a perforated plate that is a plate member having a plurality of holes; a first cavity extending in a first direction, the first cavity allowing sound waves to enter through a plurality of holes present in a first region of the perforated plate; and a second cavity extending substantially parallel to the first direction, the second cavity allowing sound waves to enter through a plurality of holes present in a second region of the perforated plate. The first cavity and the second cavity are arranged in a second direction perpendicular to the first direction. A surface of the perforated plate is orthogonal to neither the first direction nor the second direction. The first cavity and the second cavity have different lengths in the first direction.

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.

A device for superscattering a target acoustic wave may include a body having an outer surface, at least one resonator being defined within the body and extending to an opening defined within the outer surface and configured to cause the superscattering of the target acoustic wave impinging upon the body, and a motor connected to the body and configured to selectively rotate the body.

An apparatus and method are provided for a drone elimination muffler to attenuate drone exhibited by engine exhaust systems. The drone elimination muffler comprises a hollow canister having a length and a diameter, and a tuned port comprising a first end connected to the canister and a second end connected to the exhaust system. The canister operates in concert with the tuned port as a dampener configured to substantially attenuate exhaust drone, or resonance, at one or more frequencies of engine operation. A valve is configured to switch the drone elimination muffler between a closed state in which the exhaust system operates without acoustic influence due to the drone elimination muffler, and an open state in which the drone elimination muffler directly influences the acoustic properties of the exhaust system.

An apparatus and method are provided for a drone elimination muffler to attenuate drone exhibited by engine exhaust systems. The drone elimination muffler comprises a hollow canister having a length and a diameter, and a tuned port comprising a first end connected to the canister and a second end connected to the exhaust system. The canister operates in concert with the tuned port as a dampener configured to substantially attenuate exhaust drone, or resonance, at one or more frequencies of engine operation. A valve is configured to switch the drone elimination muffler between a closed state in which the exhaust system operates without acoustic influence due to the drone elimination muffler, and an open state in which the drone elimination muffler directly influences the acoustic properties of the exhaust system.

This invention refers to the energy sector and can be applied in heating systems, in particular in water heaters or boilers; in disposal systems operating on associated gas flaring. The pulsating combustion device comprises a combustion chamber and, connected thereto, an air and fuel gas supply unit and a flue duct. Said flue duct comprises at least one resonance pipe connected to the combustion chamber and at least two Helmholtz resonators located successively downstream of the at least one resonance pipe. Each of said resonators consists of a flue chamber and a flue pipe arranged downstream thereof, and natural resonance frequency of each of the Helmholtz resonators is less than combustion pulsation frequency. The invention allows to increase the pulsating combustion device efficiency with a simultaneous reduction of the noise level.