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.

A wild game call includes a bugle tube and a damper. The bugle tube includes a first end with a first aperture, a second end with a second aperture, and a wall extending from the first end to the second end. The wall defines an interior volume, and the first aperture and the second aperture provide access to the interior volume such that a flow path is defined through the bugle tube from the first end, through the second end, and out the second end. The bugle tube includes a metal and is configured to generate sound waves by vibrating responsive to air flowing along the flow path. The damper surrounds the outer surface of the wall of the bugle tube between the first end and the second end and may reduce unwanted ringing while improving the sound of the bugle call.

Elastic metamaterial designs are provided, such as an acoustic radiator or sound partition, with non-spherical shapes or apertures defined in unit cells of an elastic medium. A method for making the same includes determining a set of boundary conditions for a plurality of non-spherical shapes/apertures defined in the elastic medium, and using a gradient-based algorithm to optimize a porous media model domain for the elastic medium, where porosity is related to size dimensions of the non-spherical shape/aperture and an anisotropic elastic modulus is related to an angle of orientation of the non-spherical shape/aperture. The method may include optimizing an objective function, and obtaining a grayscale design that relates to the porosity and the anisotropic elastic modulus. Reaction diffusion equations may be used with the grayscale design to obtain a pattern for the non-spherical shapes/apertures. Methods of manufacturing may include multi-material additive manufacturing techniques.

The present disclosure relates to devices, systems, and methods for controlling and/or augmenting acoustic sounds emitted from flight vehicles, such as unmanned aerial vehicles (UAVs). For example, while in flight, a UAV may emit a characteristic sound or tone (or a plurality of such tones), which may be a result of propeller and/or motor noise. To mitigate such noise from UAVs, disclosed embodiments may include acoustic resonators that may provide additional tones to complement the sounds or tones emitted from the UAV. Namely, the acoustic resonators may be shaped, adjusted, or otherwise controlled to emit additional tones that form pleasing intervals in combination with the characteristic tone(s) from the UAV.

The present disclosure relates to devices, systems, and methods for controlling and/or augmenting acoustic sounds emitted from flight vehicles, such as unmanned aerial vehicles (UAVs). For example, while in flight, a UAV may emit a characteristic sound or tone (or a plurality of such tones), which may be a result of propeller and/or motor noise. To mitigate such noise from UAVs, disclosed embodiments may include acoustic resonators that may provide additional tones to complement the sounds or tones emitted from the UAV. Namely, the acoustic resonators may be shaped, adjusted, or otherwise controlled to emit additional tones that form pleasing intervals in combination with the characteristic tone(s) from the UAV.

Systems for magnetoacoustically transferring sound across an acoustic barrier include first and second acoustic resonators positioned on opposite sides of the barrier. Each of the first and second resonators includes an attached magnet. Via magnetic coupling between the magnets, an acoustic oscillation at the first resonator induces an oscillation of the same frequency at the second resonator. Thus sound waves absorbed at the first resonator are magnetically transferred across the barrier to the second resonator, from which they are emitted.

Passively controlled acoustic metamaterials allow transmission of low amplitude acoustic (sound) waves having a resonance frequency and reflect waves having a substantially different frequency. Such materials also reflect waves having the resonance frequency when those waves have an amplitude exceeding a threshold. High amplitude resonance waves cause a resonance membrane contained in unit cells of the metamaterial to contact a rigid structure that is positioned at a longitudinal constraint distance from the resonance membrane in each unit cell. Such contact changes the resonance frequency of the membrane, thereby causing reflection of high amplitude waves. Actively controlled acoustic metamaterials include a ferromagnetic layer on the membrane and an electromagnetic positioned in each unit cell. Activation of the electromagnetic displaces the membrane and thereby shifts the resonance frequency of the membrane, on demand.

A novel fire control and extinguishing method intended for a Fire Suppression System. This system can be mounted statically, deployed from a vehicle, or incorporated into a complete unmanned vehicle (autonomous or remotely operated) using an electrical system or thermoacoustic means to generate acoustic waves to accomplish fire control and/or fire suppression. This approach eliminates the need for a vehicle to carry chemical flame retardants/extinguishers, or other traditional fire combating means, resulting in an impactful environmental footprint reduction and a marked specific efficiency improvement. The acoustic wave is generated through thermoacoustic or mechanical means using a linear actuator of magnet-and-coil, piezoelectric, or magnetostrictive construction and operating near mechanical, electrical, and acoustic resonance to reduce system power and mass.

A novel fire control and extinguishing method intended for a Fire Suppression System. This system can be mounted statically, deployed from a vehicle, or incorporated into a complete unmanned vehicle (autonomous or remotely operated) using an electrical system or thermoacoustic means to generate acoustic waves to accomplish fire control and/or fire suppression. This approach eliminates the need for a vehicle to carry chemical flame retardants/extinguishers, or other traditional fire combating means, resulting in an impactful environmental footprint reduction and a marked specific efficiency improvement. The acoustic wave is generated through thermoacoustic or mechanical means using a linear actuator of magnet-and-coil, piezoelectric, or magnetostrictive construction and operating near mechanical, electrical, and acoustic resonance to reduce system power and mass.

An acoustic absorber includes a chamber formed from walls with a resistive portion providing the only communication between the chamber volume and ambient air. In some examples chamber walls enable selection or adjustment of chamber volume or resistive area, thereby altering the acoustic absorption spectrum below 250 Hz. In some examples the chamber volume contains fibrous filler material exhibiting no airflow resistance or acoustic absorption. Density and heat capacity of the fibrous filler material results in the chamber volume exhibiting compressibility of air within the chamber, for at least acoustic frequencies up to about 50 Hz, that is larger than adiabatic compressibility of air. That larger compressibility results in an increased acoustic absorption coefficient, for at least acoustic frequencies up to about 50 Hz, 50% to 100% larger than that of an identical chamber entirely characterized by the adiabatic compressibility of air.