A centrifugal fan noise-lowering structure includes a frame having an upper and a lower cover and a sidewall, which together internally define a receiving space communicable with an air inlet and an air outlet of the frame; a stator assembly located in the receiving space and fixedly mounted on the lower cover; and a rotor assembly correspondingly assembled to the stator assembly. The receiving space is internally defined a high pressure zone and a low pressure zone. The upper cover is provided with an airflow passage, which has an inlet located at a position corresponding to the high pressure zone, and an outlet located at a position corresponding to the low pressure zone. With the airflow passage, air in the high pressure zone can be guided to jet out to the low pressure zone to thereby reduce noise produced by the centrifugal fan during its operation.

An electronic system includes a fan module, an embedded controller, an error microphone, an active noise cancellation controller, and a micro speaker module. The error microphone is configured to output an error signal by detecting the noise level during the operation of the electronic system. According to the error signal and the fan information provided by the embedded controller, the active noise cancellation controller calculates the narrow-band noises associated with the actual single-blade fundamental frequency noise and the actual BPF fundamental frequency noise generated by the fan module, and drives the micro speaker module accordingly for providing a noise cancellation signal. The error signal may be reduced to zero by adaptively adjusting the noise cancellation signal for canceling the noises generated during the operation of the electronic system.

A vehicle heater includes a heater housing (12′), through which heating air to be heated can flow, with a heating air inlet area and with a heating air outlet area. A burner unit is arranged in the heater housing. A combustion air blower (46′) is arranged in the heater housing for delivering combustion air to the burner unit. A heat exchanger unit is arranged in the heater housing (12′). Heating air flowing through the heater housing (12′) can flow around the heat exchanger unit. A combustion air intake muffler (76) is arranged essentially in the heater housing (12′). A muffler housing (78) made in one piece with the heater housing (12′) is associated with the combustion air blower (46′).

A silencer assembly especially designed for attachment to the exhaust port of vacuum pumps and which adapts to the pumps pressure changes to regulate the outlet flow. The silencer features a perforated housing having an inner channel which connects to the discharge port of the vacuum pump and a valve assembly having a spring-loaded ball for dynamically regulating the fluid flow through the perforated housing. Once the pressure of the flow from the pump is high enough to compress a spring by pushing on a rubber ball which acts as a valve, a channel opens inside the silencer and the air can be vented through the radially distributed perforations on the housing. As the air escapes, the noise caused by the flow is reduced.

A centrifugal fan includes: a fan, blades; and a scroll casing housing the fan, the scroll casing including a discharge portion, and a scroll portion including a side wall, a circumferential wall, and a tongue portion. In the circumferential wall, at a first end between the circumferential wall and the tongue portion, and at a second end between the circumferential wall and the discharge portion, a distance between an axis of the rotational shaft and the circumferential wall is equal to a distance between the axis of the rotational shaft and a standard circumferential wall, and is greater than or equal to the distance between the first end and the second end of the circumferential wall, the circumferential wall including a plurality of extended portions between the first end and the second end of the circumferential wall.

The motor support (16) comprises an inner ring (20) able to receive an element of the motor and an outer ring (22) able to be fastened to a housing, and a means (24) of decoupling between the two coaxial rings (20; 22) comprising a plurality of pads (46) of elastomer material that are interposed between the inner ring (20) and the outer ring (22). Each pad (46) is substantially “H”-shaped in form. The two arms (46int, 46ext; 461, 462) of the «H» are separated by a distance B. Each arm (46int, 46ext; 461, 462) has a width D measured in the radial direction. The web (46a) of the “H” has a width A measured in the orthoradial direction. The ratio A/B B is greater than or equal to 1.4, and the ratio A/D is greater than or equal to 2.

A heat dissipation fan includes a fan blade assembly. The fan blade assembly includes a plurality of fan blades and a plurality of silencers connected to the plurality of fan blades and evenly arranged along a rotation direction of the plurality of fan blades. A center of gravity of the plurality of silencers coincides with a rotation center of the heat dissipation fan. At least some fan blades of the plurality of fan blades have different contact surfaces with air.

A respiratory therapy device comprising at least one fan unit for generating a respiratory airflow for carrying out respiratory therapy. The fan unit comprises a housing and at least one fan wheel rotatably mounted in the housing. Respiratory air is transported through a channel formed inside the housing, which housing comprises at least one structural element, which reduces the sound emission.

A compressor includes a rotation shaft which rotates around an axis, an impeller which press-feeds a fluid from one side in an axial direction toward an outward side in a radial direction by rotating together with the rotation shaft, a casing which surrounds the rotation shaft and the impeller and in which an exit flow channel for introducing a fluid press-fed from the impeller is formed, and an acoustic liner which is provided so as to face the inside of the exit flow channel in the casing. The acoustic liner has a plurality of open hole portions which are arranged with intervals therebetween, and acoustic spaces which communicate with the open hole portions and are independently provided for the respective open hole portions.

An air-sending device includes a housing including an inlet air passage communicating with an air inlet and an outlet air passage communicating with an air outlet, a first partition plate partitioning an interior of the housing into the inlet air passage and the outlet air passage, a bell mouth disposed around an opening defined in the first partition plate, and an impeller disposed over the first partition plate across the bell mouth and having a rotation axis that extends in a direction that intersects the first partition plate. The impeller suctions air into the inlet air passage from the air inlet, and blows out air from the air outlet through the outlet air passage. The inlet air passage guides air from the air inlet to the opening along the first partition plate, and has an air-passage wall.