Abstract: A method for manufacturing a sound-absorbing panel with a sandwich structure for reducing noise impact of an aeronautic engine includes providing a first skin of a thermoplastic polymeric material, making a plurality of micro-holes through the first skin by mechanical punching of the first skin, securing the first skin to a central layer by arranging a structural adhesive layer between the first skin and the central layer and/or by a thermal weld between the first skin and the central layer, and securing the central layer to a second skin by arranging a structural adhesive layer between the central layer and the second skin and/or by a thermal weld between the central layer and the second skin.

Abstract: An acoustic attenuation structure for a gas turbine engine includes a periodic structure having a first unit cell, the first unit cell having a first central body and a first axial tube disposed on the first central body and a second axial tube disposed on the first central body, opposite the first axial tube, each of the first axial tube and the second axial tube being in fluid communication with one another through the first central body.

Abstract: Disclosed are a speaker and a portable terminal, where the speaker includes: an active vibrating unit, including a first vibrating diaphragm vibrating for radiating a sound, and a voice coil assembly for fixing and driving the first vibrating diaphragm; a passive vibrating unit, including a second vibrating diaphragm and driven by the active vibrating unit to vibrate; and a magnetic circuit system, acting with the voice coil assembly to drive the first vibrating diaphragm of the active vibrating unit to vibrate, where the magnetic circuit system is arranged between the first vibrating diaphragm and the second vibrating diaphragm, a first acoustic cavity is defined between the magnetic circuit system and the first vibrating diaphragm, and a second acoustic cavity is defined between the magnetic circuit system and the second vibrating diaphragm.

Abstract: Compressor head fixing device, a compressor and a refrigeration device. The compressor head fixing device includes a cylinder block and a cylinder head cover, the cylinder head cover being connected to the cylinder block by a fastener, the cylinder block being provided with a compression chamber and an assembly hole configured to fix the fastener; a noise reduction chamber, provided on the cylinder block; and a communication passage, provided in the cylinder block and the cylinder head cover, and being in communication with the assembly hole, the noise reduction chamber and the compression chamber. The compressor head fixing device has a compact structure, a length of the exhaust passage is shortened and the exhaust pressure is reduced.

Abstract: A serrated stethoscope tube is disclosed herein. The serrated stethoscope tube includes a tubular body portion, the tubular body portion having an exterior surface and an interior surface, the interior surface being oppositely disposed relative to the exterior surface, and the interior surface of the tubular body portion having a plurality of channels formed therein for reducing sound wave refraction and/or reverberation.

Abstract: A stethoscope and binaural assembly are disclosed herein. The stethoscope includes a stethoscope chestpiece assembly and a binaural assembly including a first ear tube, a second ear tube, and an acoustic tube connected to the first and second ear tubes, the first ear tube being flexibly connected to the second ear tube by at least one spring member disposed inside the acoustic tube, a portion of the at least one spring member being located proximate to a sound transmission junction of the acoustic tube, the binaural assembly further including a junction blockage prevention member, the junction blockage prevention member configured to prevent one or more internal sound passageways of the sound transmission junction of the acoustic tube from becoming blocked or partially blocked by the at least one spring member when the first and second ear tubes are flexed outwardly away from one another by a user.

Abstract: A vehicle comprising: an internal combustion engine having a cylinder and an exhaust manifold for collecting exhaust gases expelled from the cylinder; an exhaust system configured to channel exhaust gases along a flow path from the exhaust manifold to an exhaust outlet, the exhaust system comprising an exhaust component configured to cause an alteration to engine-generated sound pulses passing through the exhaust component; and a sound bypass device comprising a sound inlet port at a first location on the exhaust system before a first exhaust component along the flow path and a sound outlet port at a second location on the exhaust system after the first exhaust component along the flow path, the sound bypass device being configured to transmit engine-generated sound pulses from the sound inlet port to the sound outlet port whilst preventing flow of exhaust gases from the sound inlet port to the sound outlet port.

Abstract: A car having: two front wheels; two rear wheels; a bottom wall, which delimits a lower surface, which faces a road surface and, in use, is brushed by an air flow flowing under the car; an internal combustion engine; and an exhaust system, which is coupled to the internal combustion engine and is provided with an exhaust duct, which originates from the internal combustion engine and has an end chamber, which ends with an outlet opening, through which exhaust gases are released into the atmosphere. The end chamber of the exhaust duct has at least one movable partition, which can be moved to different positions so as to change the width of the outlet opening. The movable partition delimits a lower surface of the end chamber, which faces the road surface and, in use, is brushed by the air flow flowing under the car.

Abstract: A method for producing an alveolar soundproofing structure in which a portion of a membrane of a diaphragm including an acoustic outlet is inserted into a hole of a perforated membrane which covers a cell of the alveolar structure, and the diaphragm is pressed into the cell with the perforated membrane becoming deformed and is fixed at that location. It also relates to the alveolar structure. Such a method enables different types of diaphragms to be inserted into different configurations of cells and enables the diaphragm to be fixed therein, in accordance with the sound frequencies to be processed.

Abstract: A recreational vehicle and an air conditioner therefor are provided. The air conditioner includes an indoor cover defining an indoor portion and an outdoor portion with an outdoor heat exchanger and an outdoor fan disposed in the outdoor portion and an indoor heat exchanger and an indoor fan disposed in the indoor portion. The air conditioner also includes an indoor panel defining an air inlet and an air outlet. An acoustic insert includes a solid top wall and at least one permeable side wall. The acoustic insert is positioned between the indoor panel and the indoor fan, whereby the acoustic insert dampens sound transmitted through the indoor panel.

Abstract: A sound absorbing structure includes a panel having a first side and a second side and at least one acoustic scatterer coupled to a first side of the panel. The panel may be at least partially transparent. The at least one acoustic scatterer has an opening and at least one channel. The at least one channel has a channel open end and a channel terminal end with the channel open end being in fluid communication with the opening. The panel may be utilized to separate an interior space from an exterior space.

Abstract: Frequency adjustable quarter-wavelength resonators have a movable end wall defined by a surface of a sphere that is moved within the resonator tube. The sphere can be ferromagnetic, enabling it to be moved by magnetic interactions with moving external magnetic elements, or by a variable external magnetic field, controlled by power modulation to external electromagnets. The resonators can optionally be helical or otherwise curved, and the spherical shape of the structure forming the end wall enables it to navigate curves in the resonator tube.