Abstract: A compressor has first and second enmeshed rotors: rotating about first and second axes. The first rotor is supported by a bearing system carried by a bearing case. The bearing case has at least a first port to a discharge plenum. A first sound-absorbing material is positioned within the first port.

Abstract: A compressor has first (26) and second (28; 30) enmeshed rotors rotating about first (500) and second (502; 504) axes to pump refrigerant to a discharge plenum (42). The compressor includes a muffler system (200) comprising a sound absorbing first element (232) and a sound absorbing second element (236). The second element at least partially surrounds the first element and defines a generally annular flow path portion (230) between the first element and the second element. A wall (250) at least partially surrounds the second element. A space (259) optionally containing a sound absorbing third element (261) surrounds the wall.

Abstract: A compressor has first and second enmeshed rotors: rotating about first and second axes. The first rotor is supported by a bearing system carried by a bearing case. The bearing case has at least a first port to a discharge plenum. A first sound-absorbing material is positioned within the first port.

Abstract: A liner assembly includes a plurality of aligned passages providing a large open area combined with openings much smaller than a length of the passages. The plurality of passages are disposed parallel with each other and include an opening transverse to incident sound waves. The passages are separated by walls and are blocked at an end distal from the openings. Sound waves incident on a face of the liner enter the passages and are dissipated by viscous losses. Sound energy is further dissipated as thermal energy to the walls of the passages. The long narrow passages provide the desired visco-thermal losses for sound energy in a broad frequency range.

Abstract: A compressor has first (26) and second (28; 30) enmeshed rotors rotating about first (500) and second (502; 504) axes to pump refrigerant to a discharge plenum (42). The compressor includes a muffler system (200) comprising a sound absorbing first element (232) and a sound absorbing second element (236). The second element at least partially surrounds the first element and defines a generally annular flow path portion (230) between the first element and the second element. A wall (250) at least partially surrounds the second element. A space (259) optionally containing a sound absorbing third element (261) surrounds the wall.

Abstract: An elevator cab ceiling (22) includes an upper ceiling panel (26), a lower ceiling panel (28), and a ventilation channel (30) extending between the upper ceiling panel (26) and the lower ceiling panel (28). The ventilation channel (30) extends at an oblique angle relative to the upper ceiling panel (26) and separates space between the upper (26) and lower (28) ceiling panels into an upper cavity (32) and a lower cavity (34). A plurality of partitions (36) are formed within at least one of the upper (32) or lower (34) cavities. In one example, an acoustically resistive element (42) extends at least partially along a portion of the ventilation channel (30). The plurality of partitions (36) and the acoustically resistive element (42) cooperate to reduce noise levels transmitted into an elevator cab (10) via the ventilation channel (30).

Abstract: A cooled acoustic liner useful in a fluid handling duct includes a resonator chamber 52 with a neck 56, a face sheet 86, and a coolant plenum 80 residing between the face sheet and the chamber. Coolant bypasses the resonator chamber, rather than flowing through it, resulting in better acoustic admittance than in liners in which coolant flows through the resonator chamber and neck. In one embodiment, the liner also includes a graze shield 88. Openings 40, 38 penetrate both the face sheet and the shield to establish a relatively low face sheet porosity and a relatively high shield porosity. The shielded embodiment of the invention helps prevent a loss of acoustic admittance due to fluid grazing past the liner. Another embodiment that is not necessarily cooled, includes the resonator chamber, low porosity face sheet and high porosity shield, but no coolant plenum for bypassing coolant around the resonator chamber.

Abstract: A liner assembly includes a plurality of aligned passages providing a large open area combined with openings much smaller than a length of the passages. The plurality of passages are disposed parallel with each other and include an opening transverse to incident sound waves. The passages are separated by walls and are blocked at an end distal from the openings. Sound waves incident on a face of the liner enter the passages and are dissipated by viscous losses. Sound energy is further dissipated as thermal energy to the walls of the passages. The long narrow passages provide the desired visco-thermal losses for sound energy in a broad frequency range.

Abstract: An active acoustic wall has sound-pressure detectors provided within respective cells so that a detected signal acts to oscillate an oscillation plate in the cell. A porous material on a surface is thereby provided with a high sound absorption coefficient over a wide frequency range. A space between a porous material or a perforated plate 1 on the surface and a back material fixed on a back side is divided into a plurality of sections so as to form cells 10 containing an air layer or a porous sound-absorbing material. Oscillation plates 6 are arranged within respective cells 10 so as to be driven for oscillation by oscillation-plate driving units 5. Sound-pressure detectors 7 are provided close to the porous material 1 in the cell 10 so that a detected signal is inputted to a signal-processing unit 8. The signal processing unit 8 outputs a signal to the driving unit 5 for oscillating the oscillation plate 6 such that an output of the sound-pressure detector is minimized.

Abstract: The sound attenuating device of the present invention is a bulk layer connected to a support member which forms a plurality of Helmholtz resonators. This invention is particularly useful in a vehicle where the bulk layer attenuates high frequency noise, i.e. above about 1000 Hz, while the resonators can be tuned across the device to absorb at different lower frequencies in different areas of the device.

Abstract: An acoustic sensing means such as a microphone or a thin-film sensor is located in a flowing medium. To prevent the sensing of flow generated noise, the sensing means is separated from the flowing medium by at least three stages of shielding. In a preferred embodiment, the sensing means is located within a foam shield which is located in a frame covered by a fabric shield and which is, in turn, located in a second frame covered by a second fabric shield. A spandex fabric is suitable for use in the present invention.

Abstract: An active noise control system includes sensors 16,26 which detects noise 114 and provides electronic signals to an active noise control (ANC) controller 20. The controller provides electronic anti-noise signals to a speaker 24 which is connected to, and provides acoustic anti-noise into, a plurality of active resonators 120-124. The resonators 120-124 are disposed successively along the propagation direction of the noise 114 and provide time-delayed anti-noise acoustic output signals each of which attenuates a portion of the noise 114. The phasing of the anti-noise signals from the resonators 120-124 may be accomplished by acoustic and/or electronic time delays.

Abstract: A flashback resistant burner for lean fuel/air mixtures includes apparatus for mixing a primary fuel and combustion air to form a noncombustible fuel/air mixture. Means are provided for accelerating the noncombustible fuel/air mixture to a velocity higher than the flame speed of a combustible mixture of the primary fuel and air. Means are further provided for mixing a secondary fuel with the accelerated noncombustible fuel/air mixture to form a combustible fuel/air mixture that has an equivalence ratio less than 1. Means are then provided for burning the combustible fuel/air mixture.

Abstract: A lined duct is divided into two parallel branches by means of a rigid partition. The phase speed of the fundamental mode in each branch depends on the liner configuration and can differ markedly from the free-space phase speed. When the liners in the two branches are not the same, the corresponding phase speeds will be different and a relative phase lag between the waves in the two branches results. This, in turn, leads to interference between these wave components (and their reflections) both at the exit and entrance of the parallel branch pair. This interference can be exploited for the purpose of obtaining a low-frequency attenuation which is substantially larger than the attenuation of the unpartitioned duct.