A fan system is used for dissipating heat of an electronic device. The fan system includes a fan, a hollow structure, and a control circuit. Sound waves made by the fan are transmitted to an interior of the hollow structure when the fan is operating. The control circuit is connected to the hollow structure and is configured to control deformation/deformations of the hollow structure according to a state/states of the fan and/or the electronic device, which change a volume of the interior of the hollow structure for making a resonance frequency of the hollow structure being approximate to a rotation speed of the fan or being the same as the rotation speed of the fan.

A motor-fan assembly includes an assembly housing which supports a motor assembly and a working fan assembly having a working fan rotated by the motor assembly which draws in and exhausts working air. The motor-fan assembly also includes a cooling fan assembly which provides a cooling fan rotated by the motor assembly that draws in and exhausts cooling air. The assembly housing has at least one of an inlet insert and an outlet insert through which working air or cooling air passes. The inserts are removable from the assembly housing.

The present invention discloses volute for a centrifugal fan, which comprises a volute tongue having an inner wall; wherein, the volute tongue has an enclosed noise-reducing chamber, the volute tongue has a plurality of holes for allowing the air flow to enter into the noise-reducing chamber; and a sound collector and a speaker are disposed in the noise-reducing chamber. In the present invention, during the use of the centrifugal fan, a gas flow can enter the cavity through the holes on the inner wall. The sound collector can acquire a noise signal and transmit it to a controller, and the controller calculates a noise-reduced audio signal according to the acquired signal and then controls the speaker to play the corresponding reduced noise according to the noise-reduced audio signal, so that the active noise reduction is realized. With such a structure, the vortex at the volute tongue is eliminated, thus the fan noise is reduced and the fan efficiency is improved.

A compressor includes a compressor housing containing a compressor wheel and defining an inlet duct that leads air into the compressor wheel, and a wheel shroud located adjacent the blade tips and extending upstream from the blades. An annular space is defined between the wheel shroud and an inner surface of the inlet duct. The wheel shroud defines a bleed port that extends into the annular space to bleed a portion of the air entering the compressor wheel into the annular space to be recirculated back into the main flow. A noise attenuator for attenuating compressor blade passing frequency noise is formed as a blind slot located opposite the bleed port and extending for a length L from the radially inner surface of the inlet duct toward the radially outer surface of the inlet duct.

The expandable hand-held fan having noise making means integrated thereon comprises a fan that when folded shut resembles a miniature baseball bat. Upon extending the fan, advertising indicia is printed thereon, and may be associated with sports team, logo, etc. The fan includes noise making means upon the fan, and produces noise upon movement of air across the noise making member.

Methods and systems are provided for a noise mitigating device for a turbocharger compressor. In one example, the noise mitigating device includes a set of perforated rings arranged in a recirculation passage of a compressor casing treatment. The rings of the set of perforated rings may be oriented so that apertures of one ring are offset from apertures of one or more adjacent rings, forcing air to flow through the apertures via a non-linear path while deflecting at least a portion of sounds waves generated in the compressor.

An air-sending device includes a fan and a grille provided downstream of the fan in a direction of airflow generated by the fan. The grille includes a first grille that includes a plurality of first bars spaced from each other, and a second grille that includes a plurality of second bars spaced from each other. The plurality of second bars are more densely arranged than the plurality of first bars. The second grille is provided upstream of the first grille in the direction of the airflow generated by the fan, and spaced from the first grille to face the first grille.

Blowers having noise reduction features are provided. A blower may include a main body defining an airflow path therethrough, the main body extending between and defining an inlet end and an outlet end. The blower may further include an inlet muffler provided at the inlet end. The inlet muffler includes a plurality of inlet ports, each of the plurality of inlet ports including a peripheral surface defining a port aperture therethrough. At least one of the plurality of inlet ports further includes a damper material provided on the peripheral surface of the at least one inlet port and further defining the port aperture therethrough.

A silencer for vacuum pumps which allows only for unidirectional flow and which reduces the noises caused by the air discharged at the exhaust of said pump. The silencer features baffles to divert and disrupt the flow and an umbrella check valve to ensure the unidirectionality of the discharge flow.

A compressor unit includes a compressor, an electric motor which is lined with the compressor along the horizontal direction and drives the compressor, and a sound shielding member which reduces noise generated by the compressor. The sound shielding member has a shape of surrounding the compressor on a first side, a second side and a third side of the compressor and exposing the electric motor, the first and second sides being in a depth direction perpendicular to a lined direction in which the compressor and the electric motor are lined, and the third side being opposite to another side of the compressor where the electric motor is located in the lined direction.