42results about How to "Reduce sound radiation" patented technology

A device for active noise reduction has a chamber, which is arranged laterally in relation to a gas flow, and a chamber opening constructed in one wall of the chamber. In the area of the chamber opening, a deflection device is adjustably arranged. The deflection device, in a first position, at least partially directs the gas flow running by the chamber opening into the chamber, in order to compress air there, and, in a second position, directs the gas from the chamber to the gas flow, in order to release the gas inside the chamber. The resulting alternating pressure inside the chamber is radiated through the chamber opening as sound and overlays the disturbing sound.

The invention supplied a method that can decline echo without reducing vibration of the board or diaphragm, but instead with the superficial of the board or diaphragm being densely covered with chase and gaping place.

The invention proposes a closed cavity type PVDF thin-film loudspeaker. The closed cavity type PVDF thin-film loudspeaker comprises a main structure and an impedance converter; the main structure comprises a PVD thin film, a sound absorbing material layer and a glass fiber reinforced plastics back cavity; the PVDF thin film has double-sided electrodes; the double-sided electrodes respectively leadout external electrodes; the PVDF thin film and the double-sided electrodes are subjected to insulation encapsulation, and parts of the external electrodes are exposed during the insulation encapsulation; an open surface of the glass fiber reinforced plastics back cavity is a cambered surface with a rectangular projection, and the PVDF thin film after being subjected to the insulation encapsulation is sealed and fixedly connected with the edge of the open surface of the glass fiber reinforced plastics back cavity through a sealant; the sound absorbing material layer is fixed inside the glassfiber reinforced plastics back cavity body, and the sound absorbing material layer is not in contact with the PVDF thin film; and the main structure is connected with an external standard power amplifier through the impedance converter. The closed cavity type PVDF thin-film loudspeaker provided by the invention can effectively improve the sound radiation efficiency of the PVDF thin-film loudspeaker and reduce the sound radiation behind the PVDF thin-film loudspeaker, so as to solve the problems of the driving difficulty of the PVDF thin-film loudspeaker, the poor low frequency effect and the noise pollution behind the loudspeaker.

The invention relates to a multi-stage piston compressor which comprises a compressor unit (1) having a plurality of air-cooled cylinders (10a-10c), the crankshaft (8) of said compressor unit being housed in a crankcase (6) and driving a motor unit (3) that is flange-mounted on an end face (2) on said compressor. On the opposing end face (4) of the compressor unit (1), a cooler unit (5) is arranged, mounted on said compressor unit and driven by the crankshaft (8), the integrated axial fan wheel (9) of said cooler unit blowing the generated cooling air substantially outwards along the compressor unit (1) and, in order to conduct cooling air externally in the region of said compressor unit (1), at least one air guide housing (7) which extends at least partially radially around the crankcase (6) in a curved manner being mounted on said cooler unit (5) on the air inlet side and being mounted on the compressor unit (1) crankcase (6) on the air outlet side such that the axial air flow which is generated by said axial fan wheel (9) is at least partially taken in by the air guide housing (7) and at least partially guided around the crankcase (6) in the radial direction so as to reach at least one cylinder (10a) arranged on the air outlet side of said air guide housing (7).