Abstract: An object is to provide a silencing system that can achieve both high ventilation performance and high soundproof performance, can silence a plurality of pieces of resonant sound, and has high general-purpose properties since the silencing system does not need to be designed according to a tubular member. The silencing system includes one or more silencers that are disposed in a tubular member provided to penetrate a wall separating two spaces, and satisfies “0<Re[Bn]<1” and “Im[Bn]>0” in a case where a standardized effective modulus of elasticity in an interior space of the tubular member in which the silencers are disposed is denoted by Bn.

Abstract: A ventilation assembly and methods of forming the same includes a ventilation grille having reducing acoustic bodies configured to attenuate sound of the ventilation assembly. Arrangement of the acoustic bodies can form phononic crystal to attenuate sound and can be tuned to desired sound bands to reduce sounds.

Abstract: This invention provides a noise reduction system for in-wall HVAC systems. The noise reduction system can be constructed as a box structure that can be attached to an exterior wall of a dwelling where the box structure overlaps the intake air vent and the exhaust air vent of the in-wall HVAC system. For new or remodeled construction, the noise reduction system may be built into the dwelling's exterior wall so that the amount of noise reduction system's protrusion beyond the flat surface of the exterior wall is minimized. For additional noise reduction, the noise reduction system can incorporate active and/or passive noise reduction features.

Abstract: An asymmetric butterfly plate for a steam turbine exhaust hood includes a non-symmetrical curvilinear profile having a first section that extends to a second section through a vertex. The first section has a first curvilinear profile and the second section has a second curvilinear profile that is distinct from the first curvilinear profile.

Abstract: A fan with a sound deadening box has in its body a double inlet centrifugal fan and an inlet-port sound absorber formed between the fan and a body air inlet. The fan further includes a casing-inlet-port-side air passage and triangular prism shaped first inlet-port-sound-absorber air passage. With this structure, the fan has a low pressure loss, a low input, high static pressure, and a low level of airflow collision noise.

Abstract: A sound attenuator for low frequencies in an air-conditioning duct of paper mills includes a sound attenuator frame insertable in the air-conditioning duct. At least one attenuator member operating according to the plate resonator principle has a first resonator plate, a framework, whereto the first resonator plate is attached by its inner surface, and a second plate, which is essentially parallel to the first resonator plate. The second plate is attached to the framework by its inner surface, whereby the second plate, the framework and the first resonator plate delimit at least one attenuator unit. The first resonator plate, attached to the framework, is a steel plate and is attached to the framework by laser welding and the framework comprises a pressure balancing opening.

Abstract: A system and method for reducing noise in an automotive heating, ventilation, and cooling system is described. A noise attenuation device using radial vanes upstream of a flow discontinuity, such as a bend in the ducting, and downstream of a blower fan is used to reduce noise.

Abstract: A low noise method and apparatus with the apparatus including a hood for mounting over an exhaust outlet duct to capture a fluid stream and then redirect the fluid stream to a fluid outlet in the hood through the use of smoothly curving duct that maintains the fluid flowing therethrough in a laminar flow condition with the inlet and outlet positioned such that there is no line of sight between the exhaust outlet duct and the fluid outlet duct in the hood.

Abstract: A muffler arrangement includes muffler elements arranged in rows which are oriented in each case transversely to a direction of flow. The muffler elements themselves are oriented in each case longitudinally in relation to the direction of flow. The distance between two adjacent muffler rows in this case amounts to approximately at least four times, or at least six times, the distance between two adjacent muffler elements of the equidistantly arranged muffler elements of a muffler row and/or the flow off edges of the muffler elements of at least one muffler row have guide plates. Equipping of the muffler elements of the last muffler row in the direction of flow may be dispensed with.

Abstract: The present invention discloses a parallel fan. The parallel fan includes an integrally formed fan frame having plural pairs of locating windows and a plurality of fans being respectively mounted in the plural pairs of locating windows. The parallel fan has an external single pair of power lines. Each pair of locating windows includes an inlet and an outlet for respectively enabling the fan to inhale from the inlet and discharge from the outlet.

Abstract: The open grille structure normally directly in front of a condenser coil is replaced with an acoustical barrier which is moved forward of the condenser coil. In moving the acoustical barrier forward, space results at the top, bottom and sides of the unit which can be used to provide inlet openings for inlet air. Acoustical absorption material lines the structure defining the air flow path to the coil. The modified air flow path results in a modified sound path which results in sound attenuation.

Abstract: An active noise control system for a three-dimensional space, including noise detecting means, sound generating means, noise control effect detecting means and a control device consisting of a phase of a wave signal fed from the noise detecting means wherein a plurality of noise control effect detecting means and sound generating means are disposed at a distance shorter than a wavelength of the noise to be controlled, and input signals of the respective sound generating means and output signals of the respective noise control effect detecting means are fed through filters, separately, to control the sound for active noise control. In case of an air conditioner, the noise control effect detecting means are disposed at positions where an air stream flowing through the air conditioner is not obstructed thereby.