Abstract: The invention provides an apparatus and method for stimulating a borehole of a well. The invention provides an apparatus that generates low-frequency seismic type elastic waves that propagate to the geologic formation and in order to enhance the movement of fluids in the geologic formation toward a well. The apparatus may operate automatically driven by a power source that may be located on the ground surface. The regime of operation may be determined by user input. Operation of the apparatus may carried out while production of a natural resource is ongoing.

Abstract: An apparatus for damping acoustic waves that includes a volume of fluid having actively excited acoustic waves, an enclosure disposed in the volume of fluid including delimiting surfaces which define a cavity, at least one of the delimiting surfaces being permeable to the fluid, such that fluid may be exchanged between the cavity and the volume, and at least one sound producer disposed proximate the cavity to actively excite the actively excited acoustic waves in the fluid disposed in the cavity such that acoustic waves are damped in the volume.

Abstract: A method, system and computer program product are provided for implementing dynamic noise elimination. A system frame includes a plurality of acoustical sensory devices monitoring the system for problem frequencies. The system frame includes a plurality of tubes. When the tube is open, airflow is allowed. When identified tubes are closed, quarter-wavelength attenuation is provided for a frequency in a range of frequencies, based upon a length of the tube when closed. Each of the plurality of tubes is selectively controlled to be operable open or closed at a particular length, responsive to identified problem frequencies.

Abstract: An arrangement for the active vibration compensation of an x-ray emitter includes a counteracting vibration generation unit arranged outside of the x-ray emitter for reducing a vibration produced during operation of the x-ray emitter. The counteracting vibration generation unit is actively connected to the x-ray emitter and generates a counteracting vibration that is phase-shifted by 180 degrees relative to the vibration. By attaching active counteracting vibrators in the vicinity of the vibration generator, vibrations generated by the x-ray emitter are directly reduced at the source. A further transfer of vibrations to other system parts such as a C-arm 6 is reduced and/or prevented.

Abstract: In a exhaust device for an vehicle internal combustion engine, an exhaust pipe (20) of an engine (11) branches at a branching point (B) into a downstream-side first branch pipe (32) and a downstream-side second branch pipe (33). A first silencer (36) is attached to the first branch pipe (32), and a second silencer (37) is attached to the second branch pipe (33). The first branch pipe (32) and the second branch pipe (33) are different in at least one of bending rigidity and mass so that when the first branch pipe (32) and the second branch pipe (33) are vibrated in a specific vibration frequency range, vibrations of the two branch pipes (32, 33) cancel out each other at the branching point (B).

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: An electronic device includes an enclosure for the electronic device and a duct extending from an interior to an exterior of the enclosure to exhaust airflow from the enclosure. The electronic device further includes an active noise control mechanism. The active noise control mechanism includes an internal sensor, an external sensor, and an acoustic wave generator. The internal sensor is arranged within the enclosure to sense a noise and generate an internal sensor output, and the external sensor is arranged outside of the enclosure to detect sounds and generate an external sensor output. Based on the internal sensor output and the external sensor output, the acoustic wave generator generates an acoustic wave within the duct to reduce the noise.

Abstract: Method for influencing noise, wherein a noise source (16), in particular an engine in a motor vehicle, generates the noise with a substantially periodically variable excitation, and wherein a reference variable which is characteristic of the noise source, in particular an engine speed, is present at predetermined successive supply instants (ti), comprising the method steps; reading out at least a first value (Ni?1) of the reference variable at a first supply instant (ti?1) and a second predetermined value at a second supply instant (ti); generating the reference signal (12) at at least one instant (t) between the second supply instant (ti) and a third supply instant (ti+1) as a function of the first and second values that were read out; and sending the reference signal (12) to a device for actively influencing noise (11), which generates activation signals (13) for at least one actuator (14) as a function of the reference signal (12), wherein the at least one actuator (14) emits compensation sound, which inte

Abstract: A region of air is manipulated to reflect, absorb, or redirect sound energy to prevent the sound energy from reaching a listener separated from the sound source by the region of air. The region of air may be manipulated by directing ultrasonic sound waves with a sound pressure level of at least 140 decibels at the region of air.

Abstract: An exemplary embodiment of the present invention provides a silencer. The silencer includes an enclosure with a first airflow path configured to allow air to pass through the enclosure and attenuate noise entering the enclosure. The enclosure also includes an opening configured to provide a second airflow path if the first airflow path is obstructed.

Abstract: A noise control system is directed to the path along which the noise is transmitted from the source of the noise being generated to the receiver of the noise in the passenger compartment of an automotive vehicle. The noise control system is deployed in a box structure, such as the dual bulkhead of the dashboard of the vehicle, to provide a constrained volume within which engine noise can be controlled. The dual bulkhead plenum houses an active noise control apparatus, such as a speaker or a vibrating device, between the bulkheads to be operable with a control algorithm to generate sound that can control the noise or vibrations generated by the engine. The plenum can also be treated with passive noise control materials, such as viscoelastic damping materials, acoustical foam or heavy vinyl barrier and foam to block airborne sound and vibrations, in addition to the active noise control.

Abstract: A method for fabricating an acoustic metamaterial may include providing a planar pattern of springs arranged in columns and rows and separated from each other by interconnection nodes, providing a planar pattern of mass units separated from each other by a distance corresponding to a distance between the interconnection nodes, providing an array of vertically oriented springs separated from each other by the distance between the interconnection nodes, and aligning and joining the planar pattern of springs, the planar pattern of mass units and the array of vertically oriented springs to form a layer of unit cells.

Abstract: A standing wave attenuation device is installed in a cabin of a vehicle so as to reduce a standing wave caused by external noise such as road noise. The standing wave attenuation device provides a closed loop including a feedback comb filter with a feedback loop, a microphone, a speaker, and a delay element. The delay element adjusts the phase of the output signal of the feedback comb filter such that the time needed for one-time circulation of a signal through the feedback loop matches a half period of the standing wave. An original sound including the standing wave is picked up by the microphone and subjected to processing so that the speaker produces a sound wave with the inverse phase against the phase of a sound wave constituting the standing wave, so that the standing wave is canceled out by the sound wave emitted from the speaker.

Abstract: Some embodiments of the present invention provide a system that attenuates noise from a fan exhaust of a computer system. During operation, the system monitors the noise from the fan exhaust and calculates a frequency spectrum of the noise from the monitored noise. Next, the system generates an antiphase spectrum from the frequency spectrum and generates a flow of air which exhibits a property of the antiphase spectrum. Finally, the system directs the flow of air into the fan exhaust so that the noise is attenuated by a reduction of turbulence in the fan exhaust by the flow of air.

Abstract: A noise control system operable within a box-like structure provided by the dual bulkhead plenum of the vehicle dashboard positioned within the transfer path along which the noise is being transmitted from the source of the generated noise to the receiver of the noise in the passenger compartment of an automobile. The plenum is divided into discrete chambers into each of which is provided smart materials affixed to the walls of the plenum to be operable for selectively changing a property characteristic of the chambers to vary the acoustic resonance of the plenum and change the effectiveness of controlling the transmission of noise energy therethrough. A controller is coupled to the smart materials to change said property characteristic of the smart material in response to noise cancellation requirements.

Abstract: Disclosed is a refrigerator having a noise reduction structure. According to the refrigerator, a branch pipe for reducing the intensive noise occurring from an impeller part is provided to a discharge pipe connected so that the refrigerant is discharged in a direction of a condenser from the impeller part. Therefore, the traveling sound wave of the noise traveling along the discharge pipe and the reverse sound wave traveling toward the branch pipe provided to the outer periphery of the discharge pipe meet each other, so that the both sound waves are cancelled to reduce the noise.

Abstract: A microphone for use in windy environments. The microphone uses a transducer to flood the environment outside the microphone with a high frequency (such as an ultrasonic) acoustic field. The sounds desired to be detected are mixed with the high frequency carrier, and can then be received by the microphone with less wind noise. The microphone then demodulates the desired sound signals from the high frequency carrier. The microphone can be configured in a special emitter-receiver configuration that also reduces interference from engine noise.

Abstract: The invention relates to an active noise cancellation device. The invention proposes a device and a method used to cancel the noise in an exhaust gas channel of a vehicle A noise signal is received form the exhaust gas channel, using a sound sensor, a frequency signal which has same amplitude as of noise signal but opposite phase, is generated, the generated frequency signal is acoustically mixed with the noise signal in the exhaust gas channel, using a sound converter, there by reducing the noise in the exhaust gas channel. The device also takes into account the reflection of the sound caused by an obstacle near the exhaust gas channel. A distance measuring device which is external to the active noise cancellation device provides the information about the distance between the obstacle and the exhaust gas channel. Based on the distance, the frequency signal is suitably modified to reduce the effect of sound reflections caused by the obstacle.

Abstract: A device for damping of vibrations for an item of equipment comprising a structure to which a first element and a second fragile element having to be protected from the vibrations are coupled. The device comprises first piezoelectric transducer means inserted between the structure and the first element and charged with converting energy of vibration of the structure into electric energy, at least one sensor coupled to the structure and arranged to deliver measurement signals representative of vibrations, control means electrically supplied by the electric energy generated and charged with deducing at least one amplitude of movement to compensate at least partially for the vibration, and to deliver control signals representative of each determined amplitude, and second piezoelectric transducer means inserted between the structure and the second element and charged with converting the control signals into movement to damp at least partially for the second element the vibrations.

Abstract: A thermal management system (101), comprising (a) a synthetic jet actuator (103), and (b) a processor (107) in communication with the synthetic jet actuator, the processor being adapted to receive programming instructions, and being further adapted to modify the operation of the synthetic jet actuator in response to the programming instructions.

Abstract: A noise control system is operable within a box-like structure provided by the dual bulkhead plenum of the vehicle dashboard positioned within the transfer path along which the noise is being transmitted from the source of the generated noise to the receiver of the noise in the passenger compartment of an automobile. The plenum is divided into discrete chambers into each of which is provided a counter noise generating apparatus to create a counteracting noise offsetting the noise generated at the source. The acoustic resonance of the chambers amplifies the noise control energy. The geometry of the individual chambers can be varied to optimize the packaging and sound control or shaping strategy. The sound energy permitted to pass through the plenum to the driver's side of the passenger compartment can be tuned to be different than the noise received in the passenger's side.

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 method and apparatus for providing simultaneous enhancement of transmission loss and absorption coefficient using activated cavities is presented. A layer of material is provided, and a backing plate having a plurality of cavities on the top surface of said backing plate, is disposed adjacent a top surface of said layer of material. A screen is disposed along the top surface of said cavities on said backing plate and at least one cavity includes an actuator disposed within the cavity and a control system receiving a signal from the microphone and receiving a signal from the accelerometer and providing a drive signal to the actuator to provide an acoustic output to provide simultaneous insertion loss and absorption which serves to minimize a linear combination of the signal from the microphone and the signal from the accelerometer.

Abstract: A system for reducing an acoustic load of a fluid flow includes a first pipe. The first pipe includes a first end and a second end and a first aperture and a second aperture, the first and second apertures being intermediate the first and second ends. A second pipe includes a first end and a second end and a third aperture intermediate the first and second ends. The second pipe is connected at its first end to the first pipe at the first aperture. A bypass pipe includes a first end connected to the second aperture of the first pipe and a second end connected to the third aperture of the second pipe. A method of reducing an acoustic load of a flow in a standpipe connected to a first pipe configured to carry a main flow includes providing a bypass flow from the first pipe to the standpipe.

Abstract: A noise and vibration reduction system for an engine affixed to a body and a method for reducing vibrations in the body produced by that engine during operation. The present invention is particularly related to noise and vibration reduction in auxiliary power units installed on long-haul trucks and similar types of transportation vehicles. The primary noise and vibration reduction components of the present invention include an air intake silencer, a vibration tuner, and an engine speed limiter.

Abstract: An exemplary embodiment of the present invention provides a computer system. The system includes an enclosure configured to house a plurality of electronic devices. The system also includes a fan coupled to the enclosure and configured to provide a flow of cooling air through the enclosure to cool the electronic devices. The system also includes a first airflow path configured to allow the cooling air to exit the enclosure and attenuate noise generated in the enclosure. The system also includes an auxiliary outlet configured to provide a second airflow path if the first airflow path is obstructed.

Abstract: Methods and apparatus for providing a sound suppressor device including a first plate, a second plate in opposition to the first plate, and a connector between the first and second plates such that the first plate, the second plate, and the connector define a sealed cavity containing a gas at a pressure, wherein the device has a resonant frequency selected to vibrate out-of-phase with respect to a noise source for suppressing noise from the noise source while the noise source and the device are immersed in a liquid.

Abstract: The present invention to an active muffler for an exhaust gas system of an internal combustion engine, in particular in a motor vehicle, includes a multi-shell housing having a pot-shaped top shell and a pot-shaped bottom shell, a funnel-shaped sound conducting body, which is inserted into the bottom shell and has a connection passing through the bottom shell and out of the housing, a loudspeaker, which is situated in the top shell and is attached to a flange section of the sound conducting body at a distance from the connection, such that a free inside cross section of the sound conducting body surrounded by the flange section is closed with an airtight seal, and a bypass through which an interior space of the top shell is connected to an interior space of the bottom shell so they communicate.

Abstract: An active noise control apparatus and an active noise control system for reducing noise using an active vibrator, such that edges ? of the vibrator (i.e. genesis locations of a bending moment of force caused by the vibrator) agree with positions ? on a distribution of the bending moment of force caused by noise vibration of a panel, and such that the edges ? of the vibrator are aligned with the positions ? on the panel where a sign, of the distribution of the bending moment of force over the panel caused by the noise vibration, reverses. As a result, a control vibration approximate to the noise vibration can be excited. Accordingly, when the vibrator is fixed by agreeing the edges ? of the vibrator with the positions ? determined by noise frequency desired to be reduced, noise due to a target noise frequency can be effectively reduced.

Abstract: A flexible membrane is attached to an internal wall of the fairing of a flight vehicle. The membrane is inflated with gas to achieve a shape that couples with and thereby attenuates the first acoustic resonance occurring within the volume enclosed by the fairing. A sensor senses the varying ambient atmospheric pressure during flight. A pressure regulating system includes an inflation valve and pressure relief valve. Based on the sensed ambient atmospheric pressure, this system adjusts the membrane's gauge pressure throughout the flight trajectory to maintain the desired coupling gauge pressure. Acoustic blankets can also be attached to the internal walls of the fairing to abate resonances having frequencies greater than 500 Hz. Inflating the membrane with helium enhances the attenuation otherwise obtained. Multiple membranes can be individually tuned to respectively attenuate multiple acoustic resonances.

Abstract: An aircraft includes a cabin in which at least part of the space is demarcated by trim panels and the cabin is provided with a system for the active control of ambient noise. Each trim panel is either an active panel including actuators powered by the active noise control system or a passive panel without such actuators. In addition, the trim panels of the cabin of the one type, either active or passive, are mechanically interchangeable with a panel of the other type, either passive or active, respectively. Power supply wiring for active panels is installed in the aircraft, this wiring being capable of powering all active panels which could be installed, whether said active panels are actually installed or whether interchangeable passive panels are installed. Finally, a power supply system for the active panels is installed in the aircraft and connected to the power supply wiring of the active panels.

Abstract: In one embodiment, a fan is used to generate airflow through a computer chassis to a fan air inlet. An audible frequency component of the airflow is identified and selected. A sound wave is generated having a generated frequency equal to the selected audible frequency component of the airflow. The generated sound wave is introduced into the airflow with the generated frequency out of phase with the audible frequency component of the airflow. The magnitude of the generated frequency may be selected as a function of fan speed and/or air sensed pressure within the airflow. The frequency, phase, and magnitude of the generated sound wave may be selected and enforced by a baseboard management controller.

Abstract: An electronic apparatus includes a drive for recording/reproducing a recording medium, and a sound absorbing member having a Helmholtz resonator for insulating sounds at a predetermined frequency among sounds generated by the drive.

Abstract: A method of controlling noise from a six cylinder engine that can selectively use in separate operating modes either three cylinders, four cylinders, or all six cylinders, is provided that uses a noise cancellation system to provide a cancellation sound at a first frequency representative of the engine operating mode. When the vehicle changes, for example, from a three cylinder utilization mode to six cylinder utilization mode, the method extends the provision of the noise cancellation sound, at a frequency representative of three cylinder operation, beyond the time when three cylinder mode is changed to six cylinder mode. As a result, a residual “pop” noise associated with the vehicle exhaust, that is traditionally heard during the transition period is cancelled and no longer noticeable. The method also includes implementation of a waiting time before a providing cancellation sounds of different frequencies, to avoid amplitude mismatch.

Abstract: A fan noise control apparatus is provided to facilitate the reduction of noise. According to the preferred embodiments, an acoustically transparent portion is provided to permit noise from one source to pass through to interact and cancel with another noise.

Abstract: In a method and a device for canceling the noise in an exhaust gas channel of a vehicle, a noise signal is received from the exhaust gas channel using a sound sensor, and a frequency signal which has the same amplitude and the opposite phase as the noise signal is generated. The generated frequency signal is acoustically mixed with the noise signal in the exhaust gas channel using a sound converter, there by reducing the noise in the exhaust gas channel. In addition, the temperature in the exhaust gas channel is calculated based on the received sound signal.

Abstract: In a disk array apparatus, by taking note of a first sound of a specific frequency which is a noise element of original sounds generated from a fan, a second sound whose phase is inverted to that of the first sound is generated by a structure of a cooling air flow path passing through the fan, and the second sound is synthesized with the first sound on the cooling air flow path, thereby reducing the noise. For example, an exhaust duct is located on a fan unit in an upper part of the apparatus, two flow paths extending to an exhaust port are formed in an internal structure of the exhaust duct, and the two flow paths are designed so that the difference in the flow path length therebetween becomes equivalent to half wavelength of the specific frequency.

Abstract: A method for attenuating the low-frequency noise generated at the outlet (18) of an exhaust line (14). A signal representing the noise to be attenuated is defined; a first high-frequency acoustic wave (F1) is emitted from a first transducer (22) into an attenuation region (26) of the exhaust line (14), the first acoustic wave having a carrier frequency higher than 50 kHz; and a second high-frequency acoustic wave (F1+?fcb) is emitted by a second transducer (24) into the attenuation region (26) of the exhaust line, the second acoustic wave having the carrier frequency of the first high-frequency acoustic wave (F1) and containing a low-frequency counter-noise signal (?fcb) which is out of phase with the signal representing the noise to be attenuated.

Abstract: A silencing device disposed to the outside of a fan 2 that discharges air from the interior of a device 1 to the outside. The silencing device includes a reflection plate 6 provided substantially normal to the rotation axis 2a of the fan 2, and a right-angled parallelepiped shaped duct 4 that guides air from the fan 2 to the outside of the device 1. The reflection plate 6 is disposed at the other end of the duct 4, an air discharge slit 7 is formed in at least one of the four sides of the reflection plate 6, and the distance from the fan 2 to the reflection plate 6 satisfies the relationship L=(?/2)×n. n is a natural number, and ? is the wavelength of the maximum component from among the wavelength components that constitutes the sound generated by the fan 2.

Abstract: An air induction silencer assembly includes an acoustic interference member disposed within a conduit. The acoustic interference member is tuned to acoustically cancel a selected noise energy frequency. An acoustic absorbing member is also disposed within the conduit. The acoustic absorbing member converts noise energy within the conduit into heat energy to attenuate noise energy within the air induction silencer assembly. The air induction silencer assembly connects to a flexible conduit that includes an inlet portion, an outlet portion, and a flexible joint that connects the inlet portion and the outlet portion together. The flexible joint includes a rolling lobe and a rolling surface. The rolling lobe moves along the rolling surface when the inlet portion moves relative to the outlet portion.

Abstract: Edges ? of a vibrator, that is, genesis locations of a bending moment of force caused by a vibrator, agree with positions ? on a distribution of the bending moment of force caused by noise vibration of a panel, where the sign of the distribution of bending moment of force is reversed. As a result, control vibration approximate to the noise vibration can be excited. Accordingly, when the vibrator is fixed by agreeing the edges ? of the vibrator with the positions ? determined by noise frequency desired to be reduced, noise due to a target noise frequency can be effectively reduced.

Abstract: The invention relates to an active noise cancellation device. The invention proposes a device and a method used to cancel the noise in an exhaust gas channel of a vehicle A noise signal is received form the exhaust gas channel, using a sound sensor, a frequency signal which has same amplitude as of noise signal but opposite phase, is generated, the generated frequency signal is acoustically mixed with the noise signal in the exhaust gas channel, using a sound converter, there by reducing the noise in the exhaust gas channel. The device also takes into account the reflection of the sound caused by an obstacle near the exhaust gas channel. A distance measuring device which is external to the active noise cancellation device provides the information about the distance between the obstacle and the exhaust gas channel. Based on the distance, the frequency signal is suitably modified to reduce the effect of sound reflections caused by the obstacle.

Abstract: The present invention to an active muffler for an exhaust gas system of an internal combustion engine, in particular in a motor vehicle, includes a multi-shell housing having a pot-shaped top shell and a pot-shaped bottom shell, a funnel-shaped sound conducting body, which is inserted into the bottom shell and has a connection passing through the bottom shell and out of the housing, a loudspeaker, which is situated in the top shell and is attached to a flange section of the sound conducting body at a distance from the connection, such that a free inside cross section of the sound conducting body surrounded by the flange section is closed with an airtight seal, and a bypass through which an interior space of the top shell is connected to an interior space of the bottom shell so they communicate.

Abstract: A method of controlling noise from a six cylinder engine that can selectively use in separate operating modes either three cylinders, four cylinders, or all six cylinders, is provided that uses a noise cancellation system to provide a cancellation sound at a first frequency representative of the engine operating mode. When the vehicle changes, for example, from a three cylinder utilization mode to six cylinder utilization mode, the method extends the provision of the noise cancellation sound, at a frequency representative of three cylinder operation, beyond the time when three cylinder mode is changed to six cylinder mode. As a result, a residual “pop” noise associated with the vehicle exhaust, that is traditionally heard during the transition period is cancelled and no longer noticeable. The method also includes implementation of a waiting time before a providing cancellation sounds of different frequencies, to avoid amplitude mismatch.

Abstract: Method for influencing noise, wherein a noise source (16), in particular an engine in a motor vehicle, generates the noise with a substantially periodically variable excitation, and wherein a reference variable which is characteristic of the noise source, in particular an engine speed, is present at predetermined successive supply instants (ti), comprising the method steps; reading out at least a first value (Ni?1) of the reference variable at a first supply instant (ti?1) and a second predetermined value at a second supply instant (ti); generating the reference signal (12) at least one instant (t) between the second supply instant (ti) and a third supply instant (ti+1) as a function of the first and second values that were read out; and sending the reference signal (12) to a device for actively influencing noise (11), which generates activation signals (13) for at least one actuator (14) as a function of the reference signal (12), wherein the at least one actuator (14) emits compensation sound, which interfe

Abstract: Some embodiments of the present invention provide a system that attenuates noise from a fan exhaust of a computer system. During operation, the system monitors the noise from the fan exhaust and calculates a frequency spectrum of the noise from the monitored noise. Next, the system generates an antiphase spectrum from the frequency spectrum and generates a flow of air which exhibits a property of the antiphase spectrum. Finally, the system directs the flow of air into the fan exhaust so that the noise is attenuated by a reduction of turbulence in the fan exhaust by the flow of air.

Abstract: In a method and a device for canceling the noise in an exhaust gas channel of a vehicle, a noise signal is received from the exhaust gas channel using a sound sensor, and a frequency signal which has the same amplitude and the opposite phase as the noise signal is generated. The generated frequency signal is acoustically mixed with the noise signal in the exhaust gas channel using a sound converter, there by reducing the noise in the exhaust gas channel. In addition, the temperature in the exhaust gas channel is calculated based on the received sound signal.

Abstract: The present invention relates to an active muffler for an exhaust gas system of an internal combustion engine, in particular in a motor vehicle, having at least one antinoise generator for applying antinoise to the exhaust gas, whereby the antinoise generator has a diaphragm drive with which it is coupled via at least one coupling element in a thermally conducting and noise-reducing manner to an outside wall of the muffler, which is in contact with the environment.

Abstract: A device for actively reducing sound transmission, provided with a first and second wall (3, 5) enclosing an inner space (1, 2), wherein at least the second wall (5) is provided with actuators (6), for instance eletromagnetic actuators and/or piezoeleteric elements, wherein the said inner space is provided with at least one inner wall (4) to divide this space into at least two layers of air (1, 2), which inner wall (4) is arranged such that the layers of air (1, 2) are in fluid connection with each other.

Abstract: A sound generator for a vehicle is provided, including a hollow drum having a sound radiation panel structurally and acoustically coupled thereto. The drum has an aperture formed in an outer wall thereof. The drum is adapted to be in fluid communication with an air conduit of the vehicle. The sound radiation panel covers at least a portion of the aperture and is adapted to radiate sound energy to at least one of an engine compartment and an interior of the vehicle. A vehicle system including the sound generator and a method for manufacturing the sound generator are also provided.