A novel design for desiccant air dryer pneumatic mufflers includes a core comprising a perforated inner tube with baffles attached to the outside surface of the inner tube. The inner tube is positioned in the interior of an outer tube, and a cap is positioned on one end of both tubes. The interior portion of the cap is solid so that it blocks the flow of air at the end of the inner tube, forcing the air to flow through the perforations in the inner tube and into the outer tube. The perimeter of the cap is perforated so that the air exits the muffler.

A soundproof system includes a tube structure having one or more opening ends and a soundproof structure having an opening portion or a radiation surface. The following Expression (1) is satisfied in a case in which a phase difference between sound incident on the soundproof structure and sound re-radiated from the soundproof structure is defined a phase difference as θ1; for one or more maximum values of the pressure of sound formed in the tube structure, a distance between the opening portion or the radiation surface and a position where the sound pressure has a maximum value in the tube structure is L; a wavelength of the incident sound is λ; and a phase difference θ2 is defined as 2π×2L/λ:
|θ1−θ2|≤π/2  (1). The soundproof system with a small size can obtain high transmission loss in a wide band.

A ventilation component includes a circumferential wall. At least a part of the circumferential wall is formed by the wall portion, which includes the inner layer and the outer layer. The inner layer contains fibers and has permeability, and the outer layer is provided on the radially outer side of the inner layer and has elasticity. The wall portion forms a vibration system including the inner layer as a mass portion and the outer layer as a spring portion. The vibration system has a partially varying natural frequency.

A noise reduction structure for a ventilation treatment device and the ventilation treatment device are provided. The noise reduction structure comprises a first micropore plate; the first micropore plate has a first plate surface and a second plate surface which are opposite to each other, the first plate surface is used for forming a first chamber; the second plate surface is used for forming an air passage such that air in the air passage flows along the second plate surface; the first micropore plate has a plurality of first micro-vias through which the first chamber communicates with the air passage. The noise reduction structure is wide in noise reduction frequency band, may effectively reduce aerodynamic noise in the air passage, and improves the satisfaction degree of a patient using the ventilation treatment device.

An exhaust muffler has an outer cylinder into which an exhaust gas from an engine is introduced and a muffling member made of a foamed ceramic material. The outer cylinder has an inner cylinder through which the exhaust gas passes, a part of the muffling member is supported by an outer wall of the inner cylinder via a holding member. The inner cylinder includes, in an area where the inner cylinder overlaps with the muffling member with respect to axial direction of the inner cylinder, a porous wall portion formed with communication holes communicating an inside and an outside of the inner cylinder. The holding member is arranged at a position where it does not overlap with a part of the porous wall portion, so that muffling effect is enhanced, and the muffling member having a low resistance to impact forces can be supported stably by the inner cylinder.

An exhaust pulse balance chamber comprising a circular collar, mid-section that bulges at its center, skirt, and right and left legs, all of which are sealed to the exterior environment and in fluid communication with one another. The outer diameter of the skirt increases in width but not in depth from the proximal end of the skirt to the distal end of the skirt, which is configured to receive the right and left legs. Each leg is bent at a 30-degree angle relative to the central longitudinal axis of the exhaust pulse balance chamber. The invention includes a method of using the exhaust pulse balance chamber to convert a vehicle from a dual-in, single-out exhaust system to a dual-in, dual-out exhaust system.

A noise suppressing heat exchanger (also referred to as heat sink) includes a plurality of heat dissipating fins formed with baffles. The baffles suppress noise from a fan by slowing air flow and creating internal reflections within the heat exchanger that reflect noise away from the air flow path, absorbing sound energy and potentially setting up standing waves which dissipate noise via destructive interference. Other embodiments may be described and/or claimed.

A muffler for receiving exhaust gas from a combustion engine comprises a shell, first and second inlet pipes each having outlets providing exhaust gas to a mixing chamber within the shell, a first chamber and a second chamber positioned within the shell and a pair of communication pipes each including an inlet receiving exhaust gas from the mixing chamber. Each communication pipe includes an outlet providing exhaust to the second chamber. Each of the communication pipes further includes a Helmholtz opening positioned downstream of the mixing chamber. The Helmholtz openings are open to the first chamber.

Described herein are noise attenuating ducts and vehicles using these ducts for environmental control systems. A duct comprises an exoskeleton structure and a sound-absorbing structure, disposed within and conforming to the exoskeleton structure. The exoskeleton structure provides external mechanical support to the sound-absorbing structure thereby helping to maintain the tubular shape of the sound-absorbing structure. This external support does not interfere with the airflow inside the sound-absorbing structure. Furthermore, the external positioning of the exoskeleton structure allows the integration of various support mounting features for the installation of the duct in a vehicle. In some examples, the exoskeleton structure comprises a plurality of enclosed openings to reduce the weight of the exoskeleton structure and provide additional flexibility. Furthermore, additive manufacturing of the exoskeleton structure allows achieving a monolithic structure with various features and characteristics described above.

An apparatus is provided for an aircraft propulsion system. This apparatus includes an acoustic panel and a mount. The acoustic panel includes a perforated face skin, a back skin, a perforated intermediate layer, a first cellular core and a second cellular core. The first cellular core includes a first section and a second section. The first section is between and is connected to the perforated face skin and the perforated intermediate layer. The second section is between and is connected to the perforated face skin and the back skin. The second cellular core is between and is connected to the perforated intermediate layer and the back skin. The mount is attached to the back skin along the second section.