Abstract: A sealed intake air system incorporates a positive connection seal interface between the air filter and the airbox with captive fasteners to provide a positive connection between the air filter and the one-piece airbox.

Abstract: A loudspeaker arrangement includes an air-tight, rigid, thermo-conductive enclosure (103) with an aperture (115) and an outer surface, and a loudspeaker (101) air-tightly mounted in the aperture (115) to form a locked acoustic volume within the enclosure (103). The arrangement further includes a multiplicity of thermo-conductive fins (112) attached to or integrated in the enclosure (103) at the outer surface thereof. The multiplicity of fins (112) is distributed over the outer surface of the enclosure (103).

Abstract: A process for producing noodle strips in which a dough sheet is slit into noodle strips using a rotary slitting device comprising at least a pair of cutting blade rolls, scraping members and air flow supply means. The dough sheet is passed through the cutting blade rolls, to thereby slit the dough sheet into noodle strips; the noodle strips are peeled off from the cutting blade rolls using the scraping members, to thereby separate into upper and lower noodle strip bundles; and air flow is supplied to the slit noodle strips from the air flow supply means. There is provided a process capable of stably realizing generally straight noodle strips with no strong longitudinal waves even in a mass production line.

Abstract: Engine order cancellation (EOC) systems generate feed forward noise signals based on the engine or other rotating shaft RPM and use those signals and adaptively configured W-filters to reduce the in-cabin SPL by radiating anti-noise through speakers. An EOC system may include a signal analysis controller for detecting non-stationary events, such as speech, based on parameters sampled from a current frame of error signals output from microphones positioned in various locations of a vehicle passenger cabin. Upon detection, the signal analysis controller may mitigate the effects of the non-stationary event to prevent the EOC system from boosting noise or contributing to a speech-like post-echo in the passenger cabin. For example, if speech is detected in a frame, then the adaptation can be frozen for that frame. Alternatively, the signal analysis controller may adaptively subtract voice signals out of the error microphone signal.

Abstract: Provided is a silencer including: an expansion chamber having a cuboid shape; a first pipe for being coupled to a noise source, the first pipe being coupled to an approximate center of a first surface of the expansion chamber; and a second pipe coupled to an approximate center of a second surface of the expansion chamber adjacent to the first surface. The expansion chamber has an internal space and a partition in the internal space, the partition is disposed upright on a third surface of the expansion chamber opposed to the second surface of the expansion chamber to extend from the third surface toward the second surface, and the second pipe has a central axis substantially included in the partition.

Abstract: An audio system includes a speaker configured to emit sound. The speaker is contained in an enclosure, the enclosure forming a front cavity and a rear cavity that are on opposite sides of the speaker. The enclosure includes: at least one output port configured to output a first portion of the sound from the front cavity and at least one rear port configured to output a second portion of the sound from the rear cavity. The second portion of the sound is substantially out of phase with the first portion. The audio system has an equivalent acoustic volume (Vas) greater than ten times a volume of the front cavity and greater than ten times a volume of the rear cavity.

Abstract: A gas turbine engine comprises a fan rotor having fan blades received within an outer nacelle, and the outer nacelle having an inner surface. The outer nacelle is secured to an inner portion through a mount flange at a first axial location. An acoustic treatment extends inwardly of the outer portion of the nacelle and across the axial location of the mount flange and further inwardly toward the fan blades.

Abstract: The curved flow channel with built-in lattice structure provided by the present application is configured with the lattice structure disposed at the outer inside wall of the curved section away from a center of curvature of the curved section. Through geometry and distribution design of the lattice structure, flow rate and flow direction of fluid impacting the lattice structure can be altered, which achieves the purpose of flow rate redistribution in the curved flow channel and produces a downstream flow field with uniform distribution.

Abstract: An air inlet device for a cooling device of an electric vehicle, having an air inlet duct with a duct wall delimiting a duct volume and at least one duct opening for the admission of ambient air for guiding to the cooling device. An acoustic device for pedestrian protection is arranged in the duct wall in a flow-neutral manner with respect to the flow of ambient air, with a speaker device for generating a protective noise.

Abstract: Systems and methods for reducing noise or vibration generated by an internal combustion engine are described. An engine controller is arranged to operate the working chambers of the engine in a cylinder output level modulation manner. A noise/vibration reduction unit actively control of a device that is not a part of the powertrain. The device is controlled in a feed forward manner to alter an NVH characteristic of the vehicle in a desired manner based at least in part on a characteristic of the cylinder output level modulation operation of the engine.

Abstract: A vehicle exhaust system includes a first exhaust gas path and a second exhaust gas path. At least one valve is positioned within the first exhaust gas path and an active noise control system is associated with the second exhaust gas path. An example method includes, providing the first exhaust gas path with a first tailpipe having a first outlet and the second exhaust gas path with a second tailpipe having a second outlet separate from the first outlet. The valve and the active noise control system are controlled simultaneously to control noise generated by the vehicle exhaust system.

Abstract: A noise-cancellation system for a headphone (HP) that comprises a speaker (200, 210) for emitting a speaker signal, a microphone (300, 310, 320, 330) for receiving a microphone signal and a proximity sensor (400, 410) for a receiving a proximity signal comprising quantitative information on the distance of the an object (OBJ) from the proximity sensor (400, 410) has a signal processing device (100). The signal processing device (100) is designed to generate a compensation signal based on the microphone signal, wherein the generation of the compensation signal comprises filtering with an adjustable filter characteristic. The compensation signal is combined with an audio signal in order to generate the speaker signal. The filter characteristic is adapted based on the distance.

Abstract: An automotive vehicle includes an internal combustion engine that generates exhaust gas and an exhaust system that expels the exhaust gas from the vehicle via at least one of a first exhaust conduit and a second exhaust conduit. A disturbance sensor is installed within a cabin of the vehicle, and is configured to detect a disturbance within the cabin and to output a disturbance signal indicative of the disturbance. An exhaust valve has a plurality of positions and adjusts an amount of the exhaust gas delivered to the first and second exhaust conduits. The automotive vehicle further includes an electronic hardware controller in signal communication with the at least one disturbance sensor and the exhaust valve. The controller adjusts the position of the exhaust valve based on the disturbance signal to reduce the disturbance within the cabin.

Abstract: A loudspeaker system is provided that includes a loudspeaker that is arranged in a baffle between a passenger compartment of a vehicle and the outside of the passenger compartment. The loudspeaker is configured to radiate an acoustical signal to the passenger compartment. The loudspeaker system further includes active noise control system wherein a microphone is acoustically coupled to the loudspeaker via a secondary path, and the loudspeaker is electrically coupled to the microphone via an active noise control filter.

Abstract: A system (70) for actively controlling sound propagating through exhaust systems (40) includes a controller (90), a sound generator (30), in fluid communication with an exhaust system (40), and an actuator (20), inside the sound generator and receiving a controller control signal for generating sound inside the sound generator to reduce sound inside the exhaust system. The controller identifies an increased exhaust pressure inside the exhaust system based on signals output by an error microphone (50), a temperature sensor (51), an impedance measuring bridge (52), a bus system (53), or a water sensor (54). The controller interrupts a generation of the control signal and/or interrupts an output of the control signal to the at least one actuator and/or reduces a level of the control signal output to the at least one actuator by at least 30% or at least 60% upon determining a presence of an excessive exhaust gas pressure.

Abstract: An internal combustion engine comprising: a plurality of cylinders; at least one intake manifold, which receives fresh air from the outside; a plurality of intake channels, each connecting a cylinder to the intake manifold; and an intake sound amplification device, which is provided with an amplification pipe, an insulating element sealing the amplification pipe in a tight manner, a plurality of amplification channels, each originating from a corresponding intake channel, and an amplification manifold, which, on one side, is connected to all amplification channels and, on the other side, is connected to the amplification pipe.

Abstract: Disclosed is a method of decreasing pressure fluctuation induced on a surface of a hull due to propeller cavitation by using real-time vibration information and adjusting rotation angles of two propellers of a twin-propeller ship.

Abstract: A sound generator system for motor vehicles having a housing having a central axis, the housing at least partially delimiting a sound chamber, and having at least one loudspeaker located inside the housing, wherein a first sound-conducting connecting piece having a central axis M1 is acoustically coupled to the housing, the first sound-conducting connecting piece extending the sound chamber in a direction R1 along the central axis M1. At least one second sound-conducting connecting piece having a central axis M2 is acoustically coupled to the housing, the second sound-conducting connecting piece extending the sound chamber in a direction R2 along the central axis M2, wherein direction R1 differs from direction R2.

Abstract: A turbine engine nozzle can include a primary outer wall extending from an engine core area to an annular wall terminus that surrounds an engine tail cone, to form a core nozzle. The turbine engine nozzle also includes a single engine core cowl extending from the engine core area to an annular cowl terminus to form a core compartment vent nozzle. The core compartment vent nozzle exhausts air from a core compartment in a trailing edge between the single engine core cowl and the primary outer wall.

Abstract: A quiet zone generation technique for acoustic/audio signals is proposed for mitigation of selected noise or interferences over limited areas in free space by injecting the very acoustic noise, interference, or audio feedback signals via iterative processing, generating quiet zones dynamically. This creates undesired noise-free quiet zones. Optimization loops operating iteratively to electronically process cancellation signals consist of three interconnected functional blocks: (1) an acoustic injection array, consisting of pick-up arrays to obtain the interference signals, beam forming networks for element weighting and/or re-positioning, and array elements for noise injections, (2) a diagnostic network with strategically located probes, and (3) an optimization processor with cost minimization algorithms to calculate element weights for updating.

Abstract: A method of generating a drive signal for a loudspeaker in an exhaust system of an engine of a vehicle or inside or outside a passenger cell includes providing a predetermined source signal for a desired additional sound in a time domain comprising a plurality of signal components of different frequencies; analyzing the source signal based on a phase of the source signal and/or a phase of at least one oscillation in the source signal; identifying a phase of engine noise and/or a phase of at least one oscillation existing in engine noise; shifting the phases of the source signal and/or the oscillation existing in the source signal based on phases identified in engine noise and/or in oscillation existing in engine noise, the relationship of phases of individual oscillations of the source signal among each other being preserved; and generating the drive signal based on the phase-shifted source signal.

Abstract: According to one embodiment, an electronic apparatus detects an abnormality of at least one of a first fan for a first device in a first housing and a second fan for a second device in a second housing, and includes a receiver and circuitry. The receiver receives a first signal of a first sound collected by a first microphone and a second signal of a second sound collected by a second microphone. The first sound includes a sound produced by a shaft or a bearing of the first fan. The second sound includes a sound produced by a shaft or a bearing of the second fan. The circuitry detects an abnormality of one of the first and second fans by at least using the first sound and the second sound included in the first and second signals.

Abstract: An acoustic liner may include a core with a plurality of resonator chambers, a perforated top sheet coupled to the core, and a backskin coupled to the core. A thermoacoustic speaker including nanomaterials may be coupled to at least one of the core, the backskin, and the perforated top sheet. A voltage may be applied to the thermoacoustic speaker. The thermoacoustic carbon nanotube speaker may create a dynamic excitation within a resonator chamber in the core. The dynamic excitation may change the liner acoustic impedance to achieve optimum noise attenuation over a wide range of frequencies or engine operating conditions.

Abstract: An exhaust treatment device includes first and second substrates positioned in parallel within a housing. A baffle plate supports the substrates, an inlet tube and an outlet pipe, and defines a portion of a first chamber. First ends of the substrates and a second end of the inlet tube is in fluid communication with the first chamber. A partition supports the substrates, the inlet tube and the outlet pipe and defines a portion of a second chamber separate from first chamber. Second ends of the substrates and a second open end of the outlet pipe is in fluid communication with the second chamber. All of the exhaust flows in a first direction through the inlet tube, reverses direction through the substrates and reverses direction again to flow through the outlet pipe.

Abstract: An analog-to-digital converter (ADC) may include capability to sense and/or compensate for undesired effects when receiving input from a microphone. For example, a sense node may be provided between differential inputs, and that sense node separated from the differential inputs by two or more switches. The sense node may allow for a measurement of an average voltage of the differential inputs. The average voltage may be obtained activating the switches to sample the sampling capacitors coupled to the differential inputs. That average voltage may be used as common mode (CM) data. A controller may receive the CM data, along with differential mode (DM) data, and use the CM and DM data to determine undesired effects, such as DC or AC mismatch at the microphone interface. The controller may then generate a signal for applying compensation to the differential inputs to reduce or eliminate the undesired effects.

Abstract: Aerial vehicles may be operated with discrete sets of propellers, which may be selected for a specific purpose or on a specific basis. The discrete sets of propellers may be operated separately or in tandem with one another, and at varying power levels. For example, a set of propellers may be selected to optimize the thrust, lift, maneuverability or efficiency of an aerial vehicle based on a position or other operational characteristic of the aerial vehicle, or an environmental condition encountered by the aerial vehicle. At least one of the propellers may be statically or dynamically imbalanced, such that the propeller emits a predetermined sound during operation. A balanced propeller may be specifically modified to cause the aerial vehicle to emit the predetermined sound by changing one or more parameters of the balanced propeller and causing the balanced propeller to be statically or dynamically imbalanced.

Abstract: A blading for a turbine, in particular a gas turbine, is disclosed. The blades of the blading in a section near the tip have a distribution ratio (t/l) of at least 0.70, in particular at least 0.9, and/or at most 0.97, in particular at most 0.95. A downstream flow angle (?) is at most 167°, in particular at most 165°, and at least 155°, in particular at least 160°. In addition, or alternatively, an acceleration ratio (w2/w1) is at least 1.4, in particular at least 1.5.

Abstract: A sound enhancement system of an engine of a vehicle includes a vibration sensor disposed on the casing of the engine to generate an electrical signal indicative of the engine sound. A signal processor is connected to the vibration sensor to process the electrical signal-indicative of the engine sound and generate an output audio signal. A speaker is disposed in the vehicle compartment and connected to the signal processor to receive the output audio signal and generate an enhancement sound of the engine sound.

Abstract: A mobile communication device is provided in the present disclosure. The mobile communication device includes a prompting module, a detecting module, a determining module and a control module. The prompting module includes a speaker and a vibrator. The detecting module is configured for detecting a vibrating noise corresponding vibration of the vibrator. The determining module is configured for determining whether the vibrating noise is less than a threshold value. The control module is configured for controlling an operation state of the speaker according to a determining result of the determining module. The present disclosure further provides a prompting method of the mobile communication device.

Abstract: Provided is an imaging apparatus that performs sound processing suitable for each type of AF operation according to a lens f-number so that recorded sound is clear and contains little noise. The imaging apparatus includes a lens, a microphone for recording sound, and a filter configured to reduce noise contained in an output signal of the microphone. The noise reduction level of the filter is controlled according to the lens f-number so that the noise reduction level of the filter is increased when the lens f-number is large than when the lens f-number is small.

Abstract: One embodiment of the present invention provides a system that manages the acoustic noise produced by a device. During operation, the system receives a set of acoustic characteristics for the device. The system then uses these acoustic characteristics to estimate the acoustic noise being generated by the device. Next, the system uses the estimated acoustic noise to adjust a setting in the device to manage the acoustic noise produced by the device.

Abstract: Offset cartridge microphones are provided that include multiple unidirectional microphone cartridges mounted in an offset geometry. Various desired polar patterns and/or desired steering angles can be formed by processing the audio signals from the multiple cartridges, including a toroidal polar pattern. The offset geometry of the cartridges may include mounting the cartridges so that they are immediately adjacent to one another and so that their center axes are offset from one another. The microphones may have a more consistent on-axis frequency response and may more uniformly form desired polar patterns and/or desired steering angles by reducing the interference and reflections within and between the cartridges.

Abstract: According to an aspect of the invention, an image forming apparatus includes an apparatus body, a sound absorbing device utilizing a Helmholtz resonator, and a hinged exterior cover operable to open and close relative to the apparatus body. The hinged exterior cover is a hinged cover configured to pivot about a pivot shaft arranged at a lower end portion of the hinged exterior cover. At least a part of the hinged exterior cover has a multiplex structure made by overlaying a plurality of plate-like members on one another. The sound absorbing device is formed by utilizing space between two plate-like members of the plurality of plate-like members making up the multiplex structure as a cavity of the Helmholtz resonator.

Abstract: An echo cancellation system that detects and compensations for differences in sample rates between the echo cancellation system and a set of wireless speakers based on a frequency-domain analysis of estimated impulse response coefficients. The system tracks the real and imaginary number components of the coefficients, and determines a “rotation” of the coefficients over time caused by a frequency offset between the audio sent to the speakers and the audio received from a microphone. Based on the rotation, samples of the audio are added or dropped when echo cancellation is performed, compensating for the frequency offset.

Abstract: A sound generator (1) for an exhaust system (2) of an internal combustion engine of a motor vehicle (3) includes a housing (4), with an electroacoustic converter (5) having a membrane (6) separating a housing rear volume (9) from a housing front volume (10). A connection pipe (11) connects the front volume (10) of the sound generator (1) to an exhaust gas-carrying exhaust gas line (12) fluidically and acoustically. To reduce the risk of damage to the membrane (6), for example, in case the housing (4) becomes flooded, a pressure equalization line (15) is connected by a proximal end (16) to the housing (4) on the outside and is connected fluidically with the rear volume (9) through an opening (18) in the housing. A distal end (17) of the pressure equalization line (15) is at a spaced location from the housing (4).

Abstract: A method of controlling flutter of a fan nozzle includes, for a given design of a fan nozzle, determining a vibration mode that causes a flutter characteristic of the fan nozzle and, in response to the determined vibration mode, establishing a wall thickness distribution of at least one wall of the fan nozzle to include local thick portions and local thin portions that alter the flutter characteristic.

Abstract: Apparatuses and methods to attenuate acoustic waves are provided. The method may include shifting the phases of a plurality of portions of the acoustic waves and merging the portions of the acoustic waves after phase shifting. Because, for example, the phases of the acoustic waves may be out-of-sync when being merged, the acoustic waves may be attenuated. A muffler incorporating the method of attenuating acoustic waves can include a plurality of acoustic paths, each of which may have different acoustic impedance and/or length. The acoustic paths may help the acoustic waves have out-of-sync phases after the acoustic waves passing through the acoustic paths, resulting in acoustic wave attenuation.

Abstract: A passive acoustical filter includes a first opening to receive ambient sound, a second opening to output filtered sound, and a first low pass filter element coupled between the first opening and the second opening. The first low pass filter element includes a first expansion chamber filled with a material in which a speed of sound is lower than a speed of sound in air.

Abstract: Techniques involve attenuating noise from engine exhaust from an engine. For example, an apparatus includes a first tube having an input end which receives the engine exhaust from the engine, and an output end which outputs the engine exhaust. The apparatus further includes a second tube which encircles the output end of the first tube. The second tube has an exhaust end through which the engine exhaust outputted by the output end of the first tube is allowed to escape, and a resonator end which is opposite the exhaust end. The apparatus further includes a reverse resonator disposed at the resonator end of the second tube. The reverse resonator defines a reverse resonator chamber and a reverse resonator chamber diameter which is larger than a second tube diameter defined by the second tube.

Abstract: The invention relates to a system for generating anti-noise in an exhaust-gas line (9) of a vehicle, comprising a first electro acoustic transducer (11) for generating a first acoustic signal based on an electric control signal, and being in communication with the exhaust-gas line via an acoustic line (4, 7), with the first acoustic signal entering the exhaust line in form of anti-noise after having passed the acoustic line, a second electro acoustic transducer (13) for generating an electric measurement signal representing a second acoustic signal, and being in acoustic communication with the exhaust-gas line (9) at the anti-noise coupling region, a control unit (21) for generating the control signal based on the measurement signal, and a parameterizing unit (29) for determining a conforming phase parameter and a conforming magnitude parameter for the control function used by the control unit (21) based on the transient response of the control unit.

Abstract: A controlled noise source is for attachment to an exhaust pipe of a vehicle. The noise source comprises an axially compliant member that couples to the exhaust pipe such that an enclosed internal volume of the axially compliant member is in fluid communication with the interior of the exhaust pipe. A dynamic driver is coupled to the axially compliant member. The dynamic driver oscillates the axially compliant member so as to vary the internal volume of the axially compliant member and thereby introduce controlled pressure waves to the interior of the exhaust pipe that counteract sound produced by the engine.

Abstract: The present invention relates to an active sound absorber (3) for an exhaust system (1) of an internal combustion engine, preferably of a motor vehicle, comprising a housing (7), a connecting pipe (8) for the acoustic and fluidic connecting of the housing (7) with the exhaust system (1), an active membrane (10) which in the housing (7) separates a front volume (12), fluidically connected with the connecting pipe (8), from a back volume (13), and an actuator (11) for vibration stimulation of the active membrane (10). A risk of damage by condensate in the back volume (13) can be reduced by at least one condensation line (14), which fluidically connects the back volume (13) with the front volume (12), in which vapor contained in the exhaust gas condenses, and which directs the condensate which occurs to the front volume (12).

Abstract: A method for controlling an anti-sound system includes measuring sound within an exhaust system of a vehicle, calculating a control signal based on the measured sound, calculating a thermal load to be expected of the at least one loudspeaker of the anti-sound system during operation with a control signal based on a mathematical model of a thermal behavior of the loudspeaker and/or a mechanical load to be expected of the at least one loudspeaker of the anti-sound system based on a mathematical model of a mechanical behavior the loudspeaker, comparing the calculated thermal and/or mechanical load with a specified maximum load, operating the loudspeaker with the control signal, if the calculated thermal and/or mechanical load is smaller than or equal to the maximum load, and changing the spectrum of the control signal, in order to receive a corrected control signal, if the calculated load is greater than the maximum load.

Abstract: A sound generator 103 for an anti-noise system for influencing sound waves propagating in exhaust systems or intake systems of vehicles driven by an internal combustion engine includes a loudspeaker basket 123, a membrane 122 supported by the loudspeaker basket 123, a permanent magnet 121 supported by the loudspeaker basket 123, a voice coil 126 supported by a voice coil carrier 125 and a membrane stop 150. The voice coil 126 is located within a constant magnetic field generated by the permanent magnet 121. The voice coil carrier 125 is supported by the membrane 122. The membrane stop 150 is located on the loudspeaker basket 123 adjacent to the membrane 122. The membrane stop 150 includes a projection 151 extending towards the membrane 122. An anti-noise system using the sound generator and a vehicle using the anti-noise system are also provided.

Abstract: A synthetic jet muffler includes an exit end, a propagation path for conducting a first sound wave emitted by a synthetic jet generator to the exit end, and a shroud for conducting a second sound wave emitted from the synthetic jet generator in a direction opposite to the first sound wave to the exit end, wherein the shroud is disposed so that the first and second sound waves travel different distances to effect noise cancellation at the exit end.

Abstract: An active noise control (ANC) system may be implemented to both sides of a fan, such that both directions of the noise emitting are treated to reduce the overall noise. The impact on airflow is minimal, and the technique is very effective in a broad range of low frequencies. Passive sound-absorbing materials may be included for attenuation of high frequencies. The resulting quiet fan produces a low level of noise compared to any other device based on fan, which produces the same capacity of airflow. The quiet fan may be incorporated in any mechanical system which requires airflow induction such as: computers, air conditioners, machines, and more.

Abstract: High- or medium-voltage equipment comprising an induction-activated portion, a tank surrounding the active portion and filled with a dielectric fluid, such as oil, and passive acoustic reduction means for reducing acoustic waves coming from the active portion and propagating in the dielectric fluid. According to the invention, the passive means create an interference field that divides the propagated waves into two groups of waves of opposite phase that interfere with each other in a zone that is at a distance from the walls of the tank so as to at least limit the amplitude of the waves before they make contact with said walls. The equipment provides an effective solution for significantly reducing the noise that is propagated by the dielectric fluid medium.

Abstract: An improved exhaust fan housing, and exhaust fan assembly so characterized, is generally provided. The exhaust fan housing includes a first cylindrical or conical element, a second cylindrical element interior of the first cylindrical element, and a plurality of hollow vanes traversing an annular fluid passage chamber delimited thereby and uniting the first and second cylindrical elements. A central drive chamber, delimited by the second cylindrical element, is in fluid communication with ambient air exterior of the first cylindrical element via the hollow vanes. Each hollow vane is characterized by spaced apart wall segments which unitingly terminate so as to delimit a leading edge for each hollow vane, each of the spaced apart wall segments having a free end or a closed end delimiting first and second trailing edges for the hollow vanes.

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 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.