An acoustic band-pass filter assembly includes an inlet, a microphone configured to receive acoustic energy from the inlet, and a plurality of resonator chambers disposed in series between the inlet and the microphone and configured to transmit acoustic energy between the inlet and the microphone. Each of the plurality of resonator chambers has a different cross-sectional area.

An acoustic band-pass filter assembly includes an inlet, a microphone configured to receive acoustic energy from the inlet, and a plurality of resonator chambers disposed in series between the inlet and the microphone and configured to transmit acoustic energy between the inlet and the microphone. Each of the plurality of resonator chambers has a different cross-sectional area.

An acoustic structure for beaming soundwaves from a first direction toward a second direction, may include a plurality of phononic crystals. The plurality of phononic crystals have an outer border, an internal cavity and a channel extending between the outer border and the internal cavity, wherein the channel defines an opening within the outer border. The phononic crystals are disposed such that the opening faces the second direction. Soundwaves from the first direction are beamed to the second direction by the plurality of phononic crystals.

The invention relates to a method for improving the sound quality of a sound reproduction or recording in a room, the method comprising the steps of measuring an impulse response that comprises the linear response of the room; performing a time domain analysis to determine the resonances of the room and for a chosen group of room resonances determining a corresponding group of filters that, when inserted in a sound reproduction or recording chain in said room will counteract the unwanted effect of said chosen group of room resonances on the sound quality of sound reproduction or recording made in the room. The invention further relates to a device designed to implement the method according to the invention and to the use of a measure of amplitude decay as a function of frequency of a measured impulse response of a sound reproduction or recording system in a room to determine one or more resonance frequencies, the total or partial compensation of which will improve the sound quality of sound reproductions or recordings made in the room.

The invention relates to a method for improving the sound quality of a sound reproduction or recording in a room, the method comprising the steps of measuring an impulse response that comprises the linear response of the room; performing a time domain analysis to determine the resonances of the room and for a chosen group of room resonances determining a corresponding group of filters that, when inserted in a sound reproduction or recording chain in said room will counteract the unwanted effect of said chosen group of room resonances on the sound quality of sound reproduction or recording made in the room. The invention further relates to a device designed to implement the method according to the invention and to the use of a measure of amplitude decay as a function of frequency of a measured impulse response of a sound reproduction or recording system in a room to determine one or more resonance frequencies, the total or partial compensation of which will improve the sound quality of sound reproductions or recordings made in the room.

A sound attenuating cell includes a first sound attenuating cavity defined between a first sidewall and a second sidewall. The first sidewall is opposite the second sidewall. The first sidewall includes a first undulating surface and the second sidewall includes a second undulating surface. A deflector is coupled to the first undulating surface. The deflector extends from the first undulating surface toward the second undulating surface. The first undulating surface is axially offset from the second undulating surface to define a tortuous path between the first sidewall and the second sidewall. The first sound attenuating cavity has a first end and a second end. The first end is opposite the second end, and an inlet and an outlet of the first sound attenuating cavity is defined at the first end. The sound attenuating cell includes a second sound attenuating cavity nested within the first sound attenuating cavity.

Provided are an acoustic Luneburg meta lens including a lens structure on the substrate or a lens structure connected to each other by connecting rods, wherein the lens structure includes a plurality of unit structures, the volume of the unit structures decreases from the center of the lens structure toward an edge thereof, and positions of the unit structures are determined by direction components of a polar coordinate system or a spherical coordinate system, and a method for designing the acoustic Luneburg meta lens.

Systems for magnetoacoustically transferring sound across an acoustic barrier include first and second acoustic resonators positioned on opposite sides of the barrier. Each of the first and second resonators includes an attached magnet. Via magnetic coupling between the magnets, an acoustic oscillation at the first resonator induces an oscillation of the same frequency at the second resonator. Thus sound waves absorbed at the first resonator are magnetically transferred across the barrier to the second resonator, from which they are emitted.

An ultrasonic transducer for an ultrasonic flowmeter includes a transducer housing and a transducer element arranged in the transducer housing for generating and/or receiving ultrasonic signals at least in a useful frequency range of the ultrasonic transducer. The transducer housing has an ultrasound window in the region of the transducer element for transmitting the ultrasound signals between the interior and the exterior of the transducer housing. The transducer housing has a fastening section for fastening the ultrasonic transducer to a measuring tube. The transducer housing extends with a transition section between the ultrasound window and the fastening section. The transition section of the transducer housing has, in an attenuation region, a phononic crystal with an acoustic band gap in the useful frequency range, so that the transmission of ultrasonic signals in the useful frequency range between the ultrasound window and the fastening section is at least attenuated.

According to an embodiment, a sound emitting apparatus includes a helical hollow tube and at least three sound wave sources. The helical hollow tube helically extends in a circumferential direction to form an annular shape as a whole. The first helical hollow tube includes a plurality of openings. The at least three sound wave sources are coupled to the first helical hollow tube and are configured to supply a sound wave to the first helical hollow tube.