6results about How to "Sound absorption frequency bandwidth" patented technology

The invention discloses a helicopter ducted tail rotor noise reduction lining for low-frequency line spectrum noise suppression, and belongs to the technical field of helicopter ducted tail rotor noise reduction. Ducted tail rotor noise belongs to multi-line spectrum harmonic noise, and noise energy is reduced along with increase of frequency, that is, the noise energy is concentrated in first two-order harmonic waves. And on the other hand, the ducted tail rotor is low in rotating speed and small in blade number, so that the noise frequency is low. The micro-perforated plate composite folding back cavity is used as the sound absorption unit, and two sound absorption resonance frequencies of the sound absorption unit coincide with the first two orders of harmonic noise of the tail rotor through parameter design, so that the thickness of the whole sound absorption unit is reduced, and meanwhile, the low-frequency multi-line-spectrum noise reduction performance is achieved; the weight cost is reduced, and the tail rotor noise is effectively restrained.

The invention discloses a broadband sound-absorbing Helmholtz resonator. The broadband sound-absorbing Helmholtz resonator comprises a cavity, a sound-absorbing layer, a sound-absorbing layer and a sound-absorbing layer, the one or more partition plates are arranged in the cavity and divide the space in the cavity into a plurality of cavities, every two adjacent cavities are separated through one partition plate, and the partition plates are provided with communicating structures for communicating the two adjacent cavities; and the multiple neck pipe bodies communicate with the multiple cavities in a one-to-one correspondence mode, the multiple neck pipe bodies communicate with a pipeline system to be subjected to noise reduction in parallel, and the sectional areas of the multiple neck pipe bodies are different and / or the volumes of the multiple cavities are different. According to the broadband sound absorption Helmholtz resonator provided by the embodiment of the invention, good sound absorption capability can be kept in a continuously changing frequency range, and the broadband sound absorption Helmholtz resonator has the advantages of wide sound absorption frequency band, wide applicability and the like.

The present invention discloses a muffler device suitable for an integrated stove, comprising a first muffler sheet arranged on both sides of an air inlet of the integrated stove, a second muffler sheet arranged on both sides of a volute of a fan of the integrated stove, and a third muffler sheet arranged at a back plate in a fan compartment of the integrated stove. The upper parts of the first muffler sheet and the second muffler sheet both adopt a micro-perforated plate resonance sound absorption structure with a built-in multi-slit resonance cavity, and the lower part of the second muffler sheet and the third muffler sheet both adopt a micro-perforated plate resonance sound absorption structure. The present invention makes full use of the oil fume air inlet of the integrated stove and the space of the fan compartment, while achieving efficient muffler, maintaining the original oil fume absorption effect of the integrated stove, being resistant to high temperatures, easy to clean, and having good commercial application prospects.

The utility model discloses an axial flow fan with a noise reduction device. The axial flow fan comprises a transition plate, an axial flow fan body, a supporting frame, a foaming aluminum plate, a protective cover and a ventilation plate. The protective cover covers the transition plate to form a cavity, and an axial flow fan, a supporting frame and a foaming aluminum plate are arranged in the cavity; the axial flow fan is installed on the transition plate, the ventilation plate is installed at the bottom of the protective cover, the supporting frame is installed on the transition plate, the foaming aluminum plate is installed on the supporting frame, forms an annular structure and is attached to the ventilation plate, and the foaming aluminum plate and the ventilation plate form a sound absorption cover. A gap is reserved between the foaming aluminum plate and the protective cover, and an air resonant cavity is formed after the gap is sealed through a sealing medium. According to the axial flow fan with the noise reduction device, the air resonant cavity small hole plate is a through hole type foaming aluminum plate, and the small hole diameter, the porosity and the plate thickness can be selected according to noise reduction index requirements; the air resonant cavity is a sealed cavity, can improve the noise reduction frequency band width and the noise reduction effect, and has the advantages of being compact in structure, high in adaptability, high in maintainability and the like.

The present invention discloses an acoustic superstructure cell, an acoustic superstructure gradient aperture cell and a sound absorbing structure. The acoustic superstructure cell comprises a micro-perforated plate and a polygonal labyrinth cavity arranged with a plurality of partitions. The top of the polygonal labyrinth cavity is fixedly connected to the lower surface of the micro-perforated plate, and the bottom of the polygonal labyrinth cavity is a solid. The sound wave enters the structure from the first hole on the micro-perforated plate, and forms a resonance cavity with the first hole and the first layer of the labyrinth cavity, and forms a sound absorbing cavity with the second hole and the labyrinth cavity thereafter. The broadband and thin sound absorbing structure is composed of a plurality of acoustic superstructure gradient aperture cells closely laid. The acoustic superstructure gradient aperture cell is composed of a plurality of acoustic superstructure cells closely arranged in the same row without spacing. The broadband and thin sound absorbing structure can not only realize continuous broadband sound absorption, but also reduce the thickness of the structure without changing the sound absorption effect, thereby overcoming the shortcomings of the prior art sound absorbing structure, which has a narrow sound absorption band, a large structure thickness and poor engineering applicability.