In a structure for mounting resonators to a duct, the duct including openings is provided with a plurality of duct-side mounting pieces, and the resonators formed separately from the duct and including communication ports coupled to the openings are provided with a plurality of resonator-side mounting pieces that are mounted to the duct-side mounting pieces. Coupling portions of the duct and the resonators are configured to ensure turning the resonators when the resonators are mounted to the duct. On the plurality of duct-side mounting pieces disposed with intervals in a peripheral direction of the coupling portions, mounting surfaces are formed to be opposed to turning directions of the resonators when mounting the resonators to the duct, the resonator-side mounting pieces being abutted against and mounted to the mounting surfaces. Accordingly, it is possible to turn the resonators when mounting them to the duct and improve attachment work.

An acoustic wave gate is provided. The gate includes one or more layers of metamaterial configured to be in a first state and a second state and configured to change from the first state to the second state when electrical and/or magnetic energy is applied thereto. The gate also includes at least one source configured in operational communication with the one or more layers and configured to supply at least one of electrical and magnetic energy to the one or more layers. The one or more layers are configured to (i) prevent the passage of acoustic energy through the one or more layers when in the first state and (ii) permit the passage of acoustic energy through the one or more layers when in the second state, wherein the one or more layers are configured to be stimulated in phase with the acoustic energy.

An acoustic wave gate is provided. The gate includes one or more layers of metamaterial configured to be in a first state and a second state and configured to change from the first state to the second state when electrical and/or magnetic energy is applied thereto. The gate also includes at least one source configured in operational communication with the one or more layers and configured to supply at least one of electrical and magnetic energy to the one or more layers. The one or more layers are configured to (i) prevent the passage of acoustic energy through the one or more layers when in the first state and (ii) permit the passage of acoustic energy through the one or more layers when in the second state, wherein the one or more layers are configured to be stimulated in phase with the acoustic energy.

A sound attenuating baffle mounts within the duct section of an air distribution HVAC system, a ventilation system, or other air movement system for either air or gas streams, in which the duct section can be mounted directly to a fan or incorporated into a transmission duct. The sound attenuating baffle is typically oriented in the flow direction through the duct, and includes an outer casing containing sound absorbing material therein. An internal mass layer formed of a sound barrier material is suspended within the sound absorbing material which fills the outer casing. The mass layer increases the low frequency sound attenuation of the sound attenuating baffle.

A curved phononic waveguide. In some embodiments, the curved phononic waveguide includes a sheet including a plurality of standard reflectors and a plurality of divergent reflectors. Each of the standard reflectors is associated with a respective grid point of a grid defined by a plurality of intersecting lines, each grid point being a respective intersection of two of a plurality of intersecting lines, the grid being locally periodic to within 5%, and having a local grid spacing. Each of the standard reflectors has a center separated from the respective grid point of the standard reflector by at most 1% of the grid spacing. The divergent reflectors define a waveguide among the standard reflectors, each of the divergent reflectors being an absent reflector or a reflector that is smaller than one of the standard reflectors.

An acoustic echo canceller (AEC) uses a simulated echo from an adaptive filter to cancel an actual echo from a real environment. The echo cancellation is optimal when the adaptive filter response accurately matches the environment response. This can be achieved by changing coefficients of the filter in a step-wise fashion until the filter is converged on a configuration that provides optimal results. The convergence of the filter can be negatively affected by interference due to a double talk event or by an event in which the environment is changed. The disclosed AEC is configured to respond to these disruptive events by adjusting a step-size of the adaptive algorithm used to change the coefficients.

An acoustic echo canceller (AEC) uses a simulated echo from an adaptive filter to cancel an actual echo from a real environment. The echo cancellation is optimal when the adaptive filter response accurately matches the environment response. This can be achieved by changing coefficients of the filter in a step-wise fashion until the filter is converged on a configuration that provides optimal results. The convergence of the filter can be negatively affected by interference due to a double talk event or by an event in which the environment is changed. The disclosed AEC is configured to respond to these disruptive events by adjusting a step-size of the adaptive algorithm used to change the coefficients.

A system and method for converting a passive protector earmuff to a communication and/or active noise reduction (ANR) headset include mounting active components to a frame subassembly configured for insertion into the passive earcup to divide the earcup volume into a front cavity without additional passive leak paths and a back cavity having a volume that improves speaker/driver power efficiency with a resistive vent to atmosphere. An earcup having an external shell includes a frame configured for positioning within the external shell and having a first support adapted to contact an interior of the shell and a second circumferential support cooperating with a seal to contact an ear seal plate of the earcup to form the front and back cavities. The frame may support a speaker between the front and back cavity, and secure circuitry within the back cavity.

A muffler includes a first chamber, a second chamber, an extender tube, a reverse flow tube, and a separation chamber. The first chamber is coupled to an exhaust inlet of the muffler. The extender tube is coupled to the first chamber and the second chamber. The exhaust gas flows from the first chamber to the second chamber through the extender tube in a first direction. The reverse flow tube coupled to the second chamber. The exhaust gas flows through the second chamber from the extender tube to the reverse flow tube in a second direction different than the first direction. The separation chamber that provides spatial separation between the first and second chamber.

A muffler includes a first chamber, a second chamber, an extender tube, a reverse flow tube, and a separation chamber. The first chamber is coupled to an exhaust inlet of the muffler. The extender tube is coupled to the first chamber and the second chamber. The exhaust gas flows from the first chamber to the second chamber through the extender tube in a first direction. The reverse flow tube coupled to the second chamber. The exhaust gas flows through the second chamber from the extender tube to the reverse flow tube in a second direction different than the first direction. The separation chamber that provides spatial separation between the first and second chamber.