Abstract: A noise reduction device includes: a first waveform acquisition unit configured to acquire, based on a reference signal that is obtained by detecting vibration at a first position of an exhaust duct of a gas turbine, a first waveform representing vibration of the exhaust duct; an unbalanced motor configured to apply, at a second position of the exhaust duct, vibration at a target frequency designated for the exhaust duct; a second waveform acquisition unit configured to acquire, based on a measurement signal obtained by measuring a rotation pulse of the unbalanced motor, a second waveform representing rotation of the unbalanced motor; a setting unit configured to set the target frequency based on the first waveform; and a correction unit configured to correct the target frequency, to achieve a predetermined phase difference between the first waveform and the second waveform.

Abstract: A sound pressure generator includes a tube portion having a flow path extending in a tube axial direction; a rotor having a columnar shape with a column axis extending in a direction intersecting the tube axial direction in the flow path, the rotor configured to generate sound pressure by rotating about the column axis; and a drive unit configured to drive the rotor, wherein a cross-sectional shape of the rotor sectioned across the column axis includes a pointed first tip, a pointed second tip, and a long axis along which the first tip and the second tip are aligned.

Abstract: This signal processing device comprises: an acquisition unit for acquiring an acoustic signal; a measurement unit for measuring an acoustic level of the acoustic signal for every one of first frequency bands, which are a plurality of frequency bands of a preset first bandwidth; a calculation unit that, on the basis of the plurality of acoustic levels of the first frequency bands, identifies an acoustic feature quantity indicating the separation degree from normal acoustic levels of second frequency bands, which are a plurality of frequency bands of a second bandwidth that is wider than the first bandwidth; a first determination unit for determining whether the acoustic levels measured for every one of the first frequency bands are a first threshold value or greater; and a second determination unit for determining whether the acoustic feature quantity is a second threshold value or greater.

Abstract: A silencing device includes: a flow path forming plate having a flow path forming surface for forming a wall surface of a flow path through which fluid flows; and a cavity defining portion for defining a cavity on the reverse surface side of the flow path forming plate, the reverse surface being located on the reverse side of the flow path forming surface. The flow path forming plate has formed therein a plurality of fine through-holes which are configured to provide communication between the flow path forming surface and the reverse surface and which has a diameter from 0.01 mm to 0.5 mm.

Abstract: A centrifugal compressor includes one or more impellers, a casing which covers the one or more impellers, and a silencer. The casing includes a radial passage which guides a gas flowing out from a final stage impeller to a radially outer side, and an outlet scroll passage which communicates the radial passage with an outlet. The silencer includes a perforated plate in which a plurality of acoustic holes are formed, and a space forming body which forms an acoustic space connected to the plurality of acoustic holes. A first surface of the silencer opposite to a surface of the perforated plate defining the acoustic space forms at least part of an inner surface of the casing which defines the outlet scroll passage.

Abstract: A silencing device includes: a flow path forming plate having a flow path forming surface for forming a wall surface of a flow path through which fluid flows; and a cavity defining portion for defining a cavity on the reverse surface side of the flow path forming plate, the reverse surface being located on the reverse side of the flow path forming surface. The flow path forming plate has formed therein a plurality of fine through-holes which are configured to provide communication between the flow path forming surface and the reverse surface and which has a diameter from 0.01 mm to 0.5 mm.

Abstract: An object is to provide a decompression device including a plurality of stages of orifice plates disposed in a flow passage, which generates less noise in response to sonic feedback phenomenon and gas-column resonance. A decompression device 10A includes: an upstream orifice plate 14 disposed in a duct 12 forming a flow passage for a fluid F; and a downstream orifice plate 16 disposed in the flow passage and downstream of the upstream orifice plate 14. A jet-flow interference part 22A is disposed only partially on an outlet rim portion of an orifice 18 on the upstream orifice plate 14 and configured to interfere with a jet flow discharged from the orifice 18. Positions of Karman vortices e are differentiated in a duct axial direction between regions with and without the jet-flow interference part 22A to reduce generation of noise.

Abstract: Provided are: a muffler that can suitably obtain an attenuation effect of a sound wave; and a muffling device including the same. The muffler is installed on a wall surface of a pipe conduit where a gas flows. The muffler includes: a front surface exposed to an inner surface of the pipe conduit; a bottom surface facing the front surface; and a side surface disposed between the front surface and the bottom surface and covering a space between the front surface and the bottom surface. The front surface is formed with a plurality of through-holes, and the number of through-holes arrayed in a gas flow direction is one or two, and the number thereof arrayed in a direction orthogonal to the gas flow direction is 10 or more.

Abstract: Provided are: a muffler that can suitably obtain an attenuation effect of a sound wave; and a muffling device including the same. The muffler is installed on a wall surface of a pipe conduit where a gas flows. The muffler includes: a front surface exposed to an inner surface of the pipe conduit; a bottom surface facing the front surface; and a side surface disposed between the front surface and the bottom surface and covering a space between the front surface and the bottom surface. The front surface is formed with a plurality of through-holes, and the number of through-holes arrayed in a gas flow direction is one or two, and the number thereof arrayed in a direction orthogonal to the gas flow direction is 10 or more.

Abstract: An object is to provide a decompression device including a plurality of stages of orifice plates disposed in a flow passage, which generates less noise in response to sonic feedback phenomenon and gas-column resonance. A decompression device 10A includes: an upstream orifice plate 14 disposed in a duct 12 forming a flow passage for a fluid F; and a downstream orifice plate 16 disposed in the flow passage and downstream of the upstream orifice plate 14. A jet-flow interference part 22A is disposed only partially on an outlet rim portion of an orifice 18 on the upstream orifice plate 14 and configured to interfere with a jet flow discharged from the orifice 18. Positions of Karman vortices e are differentiated in a duct axial direction between regions with and without the jet-flow interference part 22A to reduce generation of noise.

Abstract: An object is to provide a heat exchanger including a resonance-prevention baffle plate disposed between a plurality of heat transfer tubes, the resonance-prevention baffle plate being obtainable and mountable readily and at lower cost. A heat exchanger 10 disposed in a flow passage of combustion gas of a boiler or the like includes: a plurality of heat transfer tubes 14 disposed in parallel and spaced from one another, an axial direction of each heat transfer tube intersecting with the combustion gas g, inside a duct wall 12 forming the flow passage of the combustion gas g; and a resonance-prevention baffle 16 having a plate shape and disposed along the combustion gas g and between the heat transfer tubes 14, the resonance-prevention baffle including a metal foil sheet 18.