Abstract: An air-conditioning unit includes an air-conditioning case, a blower, and a cooling heat exchanger disposed at a position upstream of the blower. The blower includes a rotational shaft and a suction opening. The cooling heat exchanger includes a facing portion that overlaps with the suction opening in the axial direction and a non-facing portion that does not overlap with the suction opening in the axial direction. The air-conditioning case includes a projected region that is virtually formed by projecting the facing portion toward an upstream side of the air-conditioning case along the axial direction. The air-conditioning case defines introducing openings at positions outside of the projected region. At least a first one of the introducing openings is located on a side of the projected region opposite to at least a second one of the introducing openings.

Abstract: An air conditioner includes an air conditioning case, a blower fan, and a facing wall portion. The air conditioning case configures an air passage through which air to be blown into an interior flows. The blower fan is disposed inside the air conditioning case. The facing wall portion is disposed on an air flow upstream side of the blower fan to face a suction port of the blower fan. The air conditioning case has a facing surface that faces the facing wall portion and in which through holes are formed. The air conditioning case has a closed space formed therein on an opposite side of the facing surface with respect to the air passage and communicating with the air passage via the through holes. The through holes and the closed space form a resonator having a predetermined resonance frequency.

Abstract: A fan inspection jig includes a jig assembly having multiple spring abutment pillars for holding two sides of a fan (or a series fan) to make the fan or the series fan positioned in a suspending position. A vibration sensor is disposed in at least one of the spring abutment pillars of two sides of the fan for measuring a vibration signal of the fan in operation.

Abstract: An acoustical/vibrational noise reduction system may include a plurality of divider walls spaced from each other, generally parallel to each other, and generally parallel to a direction of transmission of acoustical and vibrational noise from a source of acoustical and vibrational energy and an information handling resource. The acoustical/vibrational noise reduction system may also include a plurality of baffle fins mechanically coupled to the plurality of divider walls, generally perpendicular to the plurality of divider walls, and substantially non-parallel to the direction of transmission of acoustical and vibrational noise from the source of acoustical and vibrational energy and the information handling resource.

Abstract: Sound-attenuating heat exchangers and methods of utilizing the same are disclosed herein. The sound-attenuating heat exchangers include an aerodynamically shaped layer, a base, an intermediate layer, and a cooled fluid containment body. The aerodynamically shaped layer defines an aerodynamically shaped surface, an opposed intermediate layer-facing surface, and a plurality of apertures. The intermediate layer defines a shaped layer-facing surface and an opposed base-facing surface. The base defines a base surface. The intermediate layer-facing surface at least partially defines a sound-attenuating volume. The base surface at least partially defines an elongate cooling conduit. The sound-attenuating volume is distinct from the elongate cooling conduit and the intermediate layer at least partially fluidly isolates the sound-attenuating volume from the elongate cooling conduit. The cooled fluid containment body at least partially defines a cooled fluid containment conduit.

Abstract: A section for a gas turbine engine according to an example of the present disclosure includes, among other things, a rotor having a hub carrying a plurality of blades, the hub rotatable about a longitudinal axis, and a seal extending outwardly from the hub to establish a sealing relationship with a plurality of vanes distributed about the longitudinal axis. A flow guide assembly is secured to an engine static structure such that a flow path is defined between the hub and the flow guide assembly. The flow path has an inlet portion defined along the seal and an outlet portion, and the flow guide assembly includes an acoustic liner that extends along the flow path.

Abstract: A flow stabilizer adapted to be disposed in an outlet passage of a rotary valve includes a main body having an axis, a first end, and a second end. A first shell is disposed at least partially within the main body, and the first shell includes an axis, a first end, and a second end. A second shell is disposed at least partially within the main body and at least partially within the first shell, and the second shell includes an axis, a first end, and a second end. The axis of the first shell is angled relative to the axis of the main body and the axis of the second shell is angled relative to axis of the main body.

Abstract: A grille is provided at a lower end portion of an air inlet, and covers a central portion of the air inlet to form an inlet opening between an outer peripheral edge of the grille and an opening edge of the air inlet in plan view. A plate member extends along an inner surface of the air inlet, and provided inside the air inlet such that an upper edge of the plate member is located more inward than a lower edge of the plate member. The upper edge of the plate member is located above the lower end of the air inlet. The lower edge of the plate member surrounds an outer periphery of the grille in plan view.

Abstract: An SCR exhaust aftertreatment device of an internal combustion engine, containing an injector for injecting a reductant, a mixing unit and an SCR catalytic converter disposed immediately downstream in the direction of exhaust flow, wherein the mixing unit exhibits a swirl element and an impact element positioned upstream of the swirl element in the direction of exhaust flow, whereby the swirl element is configured of two guide elements disposed inside one another and swirl vanes for creating a swirling motion are disposed in an inner guide element and swirl vanes, which create a counterswirling motion, are disposed between the inner guide element and the outer guide element.

Abstract: A high performance hair dryer with a low level of noise emission and greater energy efficiency due to improvements on the aerodynamic performance. The hair dryer has a functional core with specific aerodynamic features. Between the core and the external casing, material for thermal-acoustic insulation can be inserted. Within the core, a conventional or mixed type impeller can be inserted.

Abstract: The systems and methods described herein provide a quiet, light-weight, and portable system and apparatus for providing positive air pressure to a patient. The systems may include a housing with an inlet port, a vibrationally isolated blower unit positioned in an inner chamber, and an outlet port for delivery of the pressurized air from the blower unit. The inlet port and outlet port may each have a tube with dimensions that are defined in relation to the inner chamber so as to reduce the overall noise output of the system.

Abstract: A turbocharger (1) having a turbine housing (2), a compressor housing (3) which has a compressor outlet (20), and a silencer (21) which is arranged on an end region (22) on the compressor outlet (20) and which has a silencer housing (23) in which an insert part (25) is arranged so as to form at least one buffer chamber (24) which is connected via at least one opening (26) to an air-guiding duct (27). The opening (26) has an edge (28) with a radially inner corner (29) which is designed so as not to have a sharp edge.

Abstract: Disclosed are devices that include spark or particle arresting, features and muffler features. The disclosed devices may include: (a) an upstream inlet receiving exhaust gas flow; (b) a downstream outlet discharging exhaust gas flow; (c) a cylindrical body disposed between the upstream inlet and downstream outlet; and (d) a particle trap having an opening for collecting particulate matter in the exhaust gas flow, the particle trap disposed downstream of the cylindrical body on a wall of the device. The cylindrical body of the devices typically includes an annular channel permitting axial flow of gas therethrough from an upstream end of the annular channel through a downstream end of the annular channel. The downstream end of the annular channel may be configured to have openings for discharging exhaust gas flow and imparting a spiral flow to the discharged gas flow.

Abstract: An engine blower includes: an engine; a fan that is rotated by the engine; a volute case that houses the fan therein and includes an air intake port; and a sponge cover with which an exterior of the air intake port of the volute case is covered.

Abstract: A sound-proofed helicocentrifugal fan includes a helicocentrifugal propeller associated with a motor, housed in a casing formed by a central piece and respective end pieces, which pieces are perforated with holes distributed over the entire surface except for the area around the propeller. A sound-absorbing blanket surrounds the casing, and an outer casing is disposed around the entire assembly.

Abstract: A rotary reciprocating acoustic transducer for producing sound in response to an applied electrical signal has a ported tubular housing having a generally cylindrical chamber with an interior lumen which is generally symmetrical about a central axis and opposing first and second linear reciprocating electrodynamic motors mounted over the tubular housing member's first and second open end, with a reciprocating rotatable transducer vane assembly with first and second rotating vanes projecting radially away from a central, axially aligned shaft driven by the first and second linear reciprocating motors.

Abstract: A vectorized jet fan device for ventilation which is capable of directing high speed air stream discharged from the fan by a small angle at a higher flow speed for the primary purposes of efficiently meeting and utilizing space clearance and improving aerodynamic performance. The inventive device includes a splitter, through which an end silencer and a silencer is securely connected to the end of a fan. The splitter is formed so that the end silencer of a smaller diameter than the silencer can be fittingly engaged at a small degree of angle from the longitudinal axis of the fan.

Abstract: A blower for an HVAC system of a motor vehicle. A fan is supplied with airflow by a duct having a bend adjacent to the fan that causes a low-pressure region at a face of the fan. A baffle is located immediately adjacent to the fan face and collocated with at least a portion of the low-pressure region to impede airflow through the face of the fan at that location. The baffle acts to reduce unwanted low frequency noise and improves the mechanical efficiency of the fan. The baffle covers a circular segment of the fan face and may have sound-suppressing features, such as ridges formed on at least one surfaces.

Abstract: An electronic system includes a component that heats up during operation and an acoustic dampening air moving assembly. The acoustic dampening air moving assembly includes air moving blades, a motor, a support structure and a housing. The motor is attached to the air moving blades to rotate the air moving blades. The support structure supports the motor and the air moving blades within the housing. The housing and the support structure at least partially include a material selected for its acoustic dampening characteristics. The acoustic dampening air moving assembly moves air to the component to cool the component. The selected material dampens acoustic vibrations within the electronic system.

Abstract: Exemplary embodiments are directed to a cooling apparatus for cooling a power electronic device, the apparatus including at least one panel that is adapted to be thermally connected to a heat source in order to receive heat from the heat source. The panel is also adapted to be thermally in contact with an air flow in order to transfer heat from the panel. The panel includes at least one hole between a first side of the panel and a second side of the panel. The hole is adapted to attenuate a vibrating air pressure generated by an acoustic noise source and carried by the air.

Abstract: An exhaust system (1) for an internal combustion engine, in particular of a motor vehicle, has at least one exhaust tract (2), which has at least one exhaust pipe (3) which conducts exhaust gas, and has at least one active silencer (5). The active silencer (5) has a silencer housing (6) and at least one electro-acoustic converter (7), which is arranged in the silencer housing (6). At least one connection pipe (8) connects the silencer housing (6) fluidically to the exhaust pipe (3). The thermal loading of the converter (7) can be reduced if a sound propagation path (9) formed for the propagation of airborne noise in the connection pipe (8) is impermeable to thermal radiation (16) emanating from the exhaust gas in the exhaust pipe (3).

Abstract: A blower assembly including a motor, an impeller and a volute that is configured such that an inlet chamber of the volute and an outlet chamber of the volute are divided from one another by an airtight membrane and the membrane is configured to allow the transmission of pressure waves between the inlet and outlet chambers.

Abstract: An acoustic dampening sleeve for electronic equipment and a method of making the same is disclosed. An enclosure for abating noise generated therein includes a housing having a structure defining an internal chamber that has ventilation openings for the ingress and egress of cooling air. The structure cooperates with equipment disposed therein to define intake and exhaust plenums. Air outside the structure passes through the housing ingress opening, into the intake plenum, through the equipment, into the exhaust plenum, and exits the structure through the housing egress opening. The ingress and/or egress openings include baffles. The baffles comprise a resilient material defining openings in fluid communication with the internal chamber and a space outside the housing. The baffles are disposed to prevent or reduce a line of sight between the inside of the structure and the outside of the structure while maintaining open vent channels between the baffles.

Abstract: An acoustic baffle for reducing noise of a centrifugal fan includes a base for mounting with a fan outlet and a projection extending from the length of the base at a back side of the base and curving away from a top surface of the base. The projection continuously tapers along at least one side from an area proximate the base to an apex. The apex aligns with a fan tangency point, and the apex or a trough of the projection aligns with a midpoint of the outlet, when the acoustic baffle is installed in the outlet. The acoustic baffle effects a gradual variation in radial and tangential airflow at the blower outlet, to reduce fan blade passage tone.

Abstract: The invention relates to a blower arrangement for gas. The blower arrangement comprises a blower with a blower housing, at least one gas-inlet opening formed in the blower housing and gas-outlet opening, and at least one rotary-driven blower wheel arranged in the blower housing. Furthermore, the blower arrangement has at least one silencer device with at least one gas guiding element, wherein the gas-guiding element comprises a plurality of silencer openings and is designed as a gas guiding pipe. The gas guiding pipe varies its cross section along its longitudinal extension and has a wall, which is designed to be wave-like along the longitudinal extension of the gas guiding pipe. The silencer device also comprises at least one silencer chamber, which is in flow connection with the silencer openings and is arranged at least in sections laterally behind the gas guiding element.

Abstract: Silencing equipment provided with one or more flow channels through which cooling air flows has a flow channel forming member that forms the flow channel, and an acoustic absorbent member that is fixed to the flow channel forming member. A resonance type silencer is formed on a wall surface of the flow channel by providing a cavity for the resonance type silencer in the acoustic absorbent member and an aperture for the resonance type silencer in a portion of the flow channel forming member. The resonance type silencer sets a frequency of noise necessary to be reduced based on a peak frequency of noise generated by a fan. The silencing equipment further has a slide member which slides by a slide mechanism to adjust the area of the top of the aperture. The silencing equipment for electronic devices capable of cooling heat generating sections thereof with air has a small and simple structure and can improve a silencing effect by blowing air.

Abstract: A low-profile, compact fan coil ceiling unit with closely coupled silencers includes a heating and cooling section, a closely coupled inlet silencer, and a closely coupled outlet silencer. The inlet silencer has a rectangular housing with a downwardly facing entry opening and a side facing exit opening attached to the inlet end opening of the heating and cooling section. The outlet silencer has a rectangular housing with a downwardly facing exit opening and a side facing entry opening attached to the outlet end opening of the heating and cooling section. Baffles to control the flow of air and reduce noise in the inlet silencer and the outlet silencer are provided.

Abstract: A method and system for reducing or eliminating banding in a rendering device caused by pressure pulsations from a blower. The pressure pulsation frequency resulting from a plurality of pressure pulsations propagated from a blower can be reduced by forming an obstruction device at an outlet of the blower. Total airflow and total pressure propagated by the blower are maintained by modifying or removing an existing restrictor plate thereby reducing acoustic noise associated with the pressure pulsations in a xerographic cavity.

Abstract: A muffler unit for a fume extractor hood includes an active noise suppression system, at least one loudspeaker, and at least two microphones connected to a control unit, and a passive noise suppression system having sound-absorbent material disposed between the microphones. The muffler unit further includes a conduit with upper fixing element and lower fixing element designed to be removably fixed to a motor unit and to a conveyor plate of the hood.

Abstract: A device for reducing sound from an air treatment unit includes, in one embodiment, an air treatment system, including a wall mount HVAC unit with a supply air opening and a return air opening. A supply air sound reducer is provided in communication with the supply air. The supply air sound reducer includes a housing defining a supply interior provided with sound reducing material. The sound reducing material is overlaid with a layer of perforated material. A return air sound reducer is provided in communication with the return air opening. The return air sound reducer includes a housing defining an interior return volume provided with sound reducing material applied to one or more inside surfaces of the interior return volume and a layer of perforated material disposed over the sound reducing material. Mid-structure including sound reducing material is disposed in each of the supply and return air assemblies.

Abstract: A rotor windage noise damping system for an induction motor cooling vent A duct having a duct airflow path has a proximal end opening in communication with the cooling vent and the distal end opening is for communication with ambient air. The duct includes a plurality of baffles. The baffles are oriented in a generally parallel mutually spaced symmetrical or asymmetrical array relative to each other and the duct airflow path. Dimensions for baffle array symmetry or asymmetry, parallel spacing, baffle thickness and baffle inset from one of the duct openings are chosen to restrict distance between adjacent baffles to less than a wavelength of windage noise at selected propagation frequencies, yet provide for sufficient cooling airflow through the duct. The duct may be tuned to dampen selected propagation frequencies by changing the baffle array.

Abstract: An apparatus and method for attenuating the sound generated by a fan powered terminal unit or other equipment in an HVAC (heating, ventilating, and air conditioning) system is described. The apparatus utilizes internal geometry to minimize noise due to air disturbances and aerodynamic effects within the apparatus. Specifically, a silencer is described comprising a casing having an inlet and an outlet; a condensate deflector positioned at the inlet to the casing; at least one baffle being operable to attenuate noise in a gas flowing through the silencer; and an air pathway through the silencer, defined by positions of the condensate deflector and the at least one baffle within the casing. The air pathway is angled or curved to substantially minimize the line-of-sight pathway from the inlet to the outlet.

Abstract: The invention relates to a blower arrangement for gas. The blower arrangement comprises a blower with a blower housing, at least one gas-inlet opening formed in the blower housing and gas-outlet opening, and at least one rotary-driven blower wheel arranged in the blower housing. Furthermore, the blower arrangement has at least one silencer device with at least one gas guiding element, wherein the gas-guiding element comprises a plurality of silencer openings and is designed as a gas guiding pipe. The gas guiding pipe varies its cross section along its longitudinal extension and has a wall, which is designed to be wave-like along the longitudinal extension of the gas guiding pipe. The silencer device also comprises at least one silencer chamber, which is in flow connection with the silencer openings and is arranged at least in sections laterally behind the gas guiding element.

Abstract: A heating or cooling system comprising a powered fan held in a duct assembly. The powered fan generates acoustic noise when blowing air. The system also comprises an acoustic wave modulator held in the duct assembly. The acoustic wave modulator has one or more fins and is configured to reduce turbulence of the air traveling through the duct assembly.

Abstract: An air conditioner includes a cabinet configured to define an outer appearance of the air conditioner. The air conditioner also includes a front panel coupled to the cabinet and having an intake hole. The air conditioner further includes a fan assembly positioned within the cabinet and configured to guide a flow of air in the cabinet. The air conditioner further includes an intake panel configured to move to open or close the intake hole in response to a control signal. In addition, the air conditioner includes at least one noise reducing part positioned in the intake panel and configured to reduce a noise having at least one frequency bandwidth.

Abstract: An exemplary fan assembly includes a fan and a muffler. The fan includes an air outlet. The muffler is disposed at the air outlet of the fan. The muffler includes a base plate. The base plate defines vents therein and blades thereon corresponding to the air outlet of the fan. The blades extend from the base plate toward the fan. An electronic device incorporating the fan assembly is also provided.

Abstract: A noise suppression characteristics adjustment method includes adjusting noise suppression characteristics of a noise suppressor, which includes a muffler having a reflection plate for reflecting sound from the cooling fan, the reflection plate being provided at a position in the cooling duct confronting an intake plane of the cooling fan and formed substantially parallel to the intake plane. A sound-absorbing part of the muffler is provided on the reflection plate. A distance d between the reflection plate and the intake plane is set such that d<c/(2×f) where f is a sound-absorption frequency of the muffler and c is a speed of sound. The muffler is located inside the cooling duct. A through-hole is provided in the reflection plate. The through hole includes a plurality of through-holes. A resonance frequency of the resonator sound absorber is adjusted by blocking at least one of the plurality of through-holes.

Abstract: Disclosed herein is a sound absorbing system used for an electronic device that has enhanced noise reduction capabilities, while maintaining the cooling performance of the device and without increasing the size of the device. A disk array has multiple fans installed on each of the right and left sides of its front section. A frame that houses a sound absorbing system is placed in the middle of an airflow path through which air passes from the fans. Two sound absorbers are arranged inside the frame such that each of the sound absorbers faces the right-side or left-side fans. Airflow paths through which air passes from the fans are located in the space between the two sound absorbers. The airflow paths are partitioned by an acoustic board such that each of the airflow paths does not have parallel side faces. The frame, the sound absorbers, the acoustic board, and the airflow paths constitute the sound absorbing system.

Abstract: A filter bank is provided. The filter bank includes a housing having a front face and a back face. Air flows along an air flow path from the front face to the back face. A filter layer is held in the housing. The filter layer is oriented between the front and back faces such that air flows through the filter layer before discharging from the back face. An attenuation layer is positioned within the housing to attenuate sound as the sound propagates between the front and back faces. The attenuation layer is oriented to extend along the air flow direction.

Abstract: In order to provide sound absorbing structure capable of reducing the noise of electronic equipment while maintaining the cooling capability of the electronic equipment, there is provided sound absorbing structure in which a plurality of penetrating openings are provided by arranging a plurality of acoustic materials having a predetermined shape at predetermined intervals in a flow channel of cooling fluid from a blower, and the plurality of acoustic materials are arranged so that the sound vertically incident on a penetrating plane of the penetrating openings from the blower does not directly go out of the electronic equipment.

Abstract: A sound attenuation canopy for reducing levels of sound passing through an opening comprises a sound absorbing member. The sound absorbing member is comprised of a flexible sound absorbing material and has a first end, a second end and an intermediate portion extending between the first end and the second end. The first end is configured to attach to a periphery of the opening at a first location, the second end is configured to attach to a periphery of the opening at a second location and the intermediate portion is configured to be spaced apart from the opening. When the first end and the second end of the sound absorbing member are attached to the periphery of the opening, at least one side opening is at least partially defined by the intermediate portion and the perimeter of the opening, and a sound transmission flow path through open space between the opening and the side opening comprises at least one change of direction greater than 45 degrees.

Abstract: A noise suppression characteristics adjustment method includes adjusting noise suppression characteristics of a noise suppressor, which includes a muffler having a reflection plate for reflecting sound from the cooling fan, the reflection plate being provided at a position in the cooling duct confronting an intake plane of the cooling fan and formed substantially parallel to the intake plane. A sound-absorbing part of the muffler is provided on the reflection plate. A distance d between the reflection plate and the intake plane is set such that d<c/(2×f) where f is a sound-absorption frequency of the muffler and c is a speed of sound. The muffler is located inside the cooling duct. A through-hole is provided in the reflection plate. The through hole includes a plurality of through-holes. A resonance frequency of the resonator sound absorber is adjusted by blocking at least one of the plurality of through-holes.

Abstract: A fan system includes a rotor supported for rotation about a fan axis. The rotor has a central hub and a plurality of blades each extending outwardly from the hub to a tip. The rotor blades define a rotor plane perpendicular to the fan axis. A first acoustic resonator has an opening disposed on a first side of the rotor plane and a second acoustic resonator has an opening disposed on a second side of the rotor plane. The acoustic resonators are configured to provide a dipole resonator system operable to at least partially reduce a blade pass frequency tone in an upstream and a downstream direction simultaneously.

Abstract: A computer system includes a chassis with a fan installed therein, a cover plate adapted to be attached to the chassis, and a noise absorber attached to the cover plate. The fan is capable of generating an amount of air flow for cooling at least a component in the chassis. The noise absorber includes a plurality of protrusions facing the fan and capable of damping the air flow that impacts the cover plate and decreasing an acoustic noise level of the computer system.

Abstract: A cooling system includes a plurality of fans and a fan bracket accommodating the fans. Each fan comprises a fan intake and a fan outlet. The fan bracket defines a plurality of air inlets and a plurality of air outlets therein. The fan bracket is provided with a fan guard in each air outlet and a plurality of noise-reducing holes in the fan guard. The air inlets of the fan bracket communicate with the fan intakes and the air outlets of the fan bracket communicate with the fan outlets, respectively. Airflow generated by the fans through the fan outlets comprises a portion exiting through the noise-reducing holes.

Abstract: A noise suppressor for an apparatus having a cooling fan and cooling duct includes a muffler including a reflection plate for reflecting sound from the cooling fan, the reflection plate being provided at a position in the cooling duct confronting the intake plane of the cooling fan and formed substantially parallel to the intake plane. A sound-absorbing part of the muffler is provided on the reflection plate, and a distance d between the reflection plate and the intake plane is set such that d<c/(2×f) where f is the sound-absorption frequency of the muffler and c is the speed of sound.

Abstract: In an appliance, such as a cyclonic vacuum cleaner, a motor is arranged to drive an impeller fan located in a motor and fan unit. The rotation of the impeller may cause nuisance tones to be generated. A silencing arrangement is provided to control such noise and includes a plurality of discrete passive silencers in the form of tube silencers arranged in a first set and a second set. The tube silencers have open end portions arranged to face the fan and the silencers of the first set are spaced from the silencers of the second set in both axial and radial directions. This combination gives the same effect as an array of closely spaced tube silencers—however, by spacing the silencers in two directions, fluid is allowed to flow freely.

Abstract: A muffling device has a muffling piece that is placed in an airflow path and muffles sound caused by airflow, and a drive unit that performs one of rotation and movement of the muffling piece.

Abstract: An apparatus and method for attenuating the sound generated by a fan powered terminal unit or other equipment in an HVAC (heating, ventilating, and air conditioning) system is described. The apparatus utilizes internal geometry to minimize noise due to air disturbances and aerodynamic effects within the apparatus. Specifically, a silencer is described comprising a casing having an inlet and an outlet; a condensate deflector positioned at the inlet to the casing; at least one baffle being operable to attenuate noise in a gas flowing through the silencer; and an air pathway through the silencer, defined by positions of the condensate deflector and the at least one baffle within the casing. The air pathway is angled or curved to substantially minimize the line-of-sight pathway from the inlet to the outlet.

Abstract: Embodiments of the present invention relate to a system and method for noise suppression. Specifically, embodiments of the present invention include a resonator configured to suppress noise from an electric fan. The resonator may comprise an enclosure having an outer perimeter, a major opening through the enclosure and defining an inner perimeter of the enclosure, a minor opening disposed along the inner perimeter, and a chamber coupled to the minor opening within the enclosure between the inner and outer perimeters.