A method includes transmitting a focused ultrasound wave into a medium to form (i) an ultrasound intensity well within the medium that exhibits a first range of acoustic pressure and (ii) a surrounding region of the medium that surrounds the ultrasound intensity well and exhibits a second range of acoustic pressure that exceeds the first range of acoustic pressure. The method further includes confining an object within the ultrasound intensity well. Additionally, an acoustic lens is configured to be acoustically coupled to an acoustic transducer. The acoustic lens has a varying longitudinal thickness that increases proportionally with respect to increasing azimuth angle of the acoustic lens. Another acoustic lens is configured to be acoustically coupled to an acoustic transducer. The acoustic lens includes a plurality of segments. Each of the plurality of segments has a varying longitudinal thickness that increases proportionally with respect to increasing azimuth angle of the segment.

A method includes transmitting a focused ultrasound wave into a medium to form (i) an ultrasound intensity well within the medium that exhibits a first range of acoustic pressure and (ii) a surrounding region of the medium that surrounds the ultrasound intensity well and exhibits a second range of acoustic pressure that exceeds the first range of acoustic pressure. The method further includes confining an object within the ultrasound intensity well. Additionally, an acoustic lens is configured to be acoustically coupled to an acoustic transducer. The acoustic lens has a varying longitudinal thickness that increases proportionally with respect to increasing azimuth angle of the acoustic lens. Another acoustic lens is configured to be acoustically coupled to an acoustic transducer. The acoustic lens includes a plurality of segments. Each of the plurality of segments has a varying longitudinal thickness that increases proportionally with respect to increasing azimuth angle of the segment.

The type of acoustic absorber comprises a micro-perforated plate, a cavity behind the micro-perforated plate, a slender and curved main acoustic propagation passage communicating with the cavity, and a set of acoustic filters arranged along the main acoustic propagation passage. These acoustic filters have different cut-off frequencies and are arranged in the order of the cutoff frequencies from high to low from the open end to the closed end of the main acoustic propagation passage. The acoustic filter comprises a section of the main acoustic propagation passage and at least one cavity communicating with the main acoustic propagation passage. The type of acoustic absorber is characterized by adopting a main acoustic propagation passage to provide different phase delay for a micro-perforated plate to realize that a micro-perforated plate effectively absorbs broadband acoustic waves, and by combing the close arrangement of main acoustic propagation passage to achieve the ultra-thin structure.

The type of acoustic absorber comprises a micro-perforated plate, a cavity behind the micro-perforated plate, a slender and curved main acoustic propagation passage communicating with the cavity, and a set of acoustic filters arranged along the main acoustic propagation passage. These acoustic filters have different cut-off frequencies and are arranged in the order of the cutoff frequencies from high to low from the open end to the closed end of the main acoustic propagation passage. The acoustic filter comprises a section of the main acoustic propagation passage and at least one cavity communicating with the main acoustic propagation passage. The type of acoustic absorber is characterized by adopting a main acoustic propagation passage to provide different phase delay for a micro-perforated plate to realize that a micro-perforated plate effectively absorbs broadband acoustic waves, and by combing the close arrangement of main acoustic propagation passage to achieve the ultra-thin structure.

An acoustic structure includes a plate and at least one acoustic scatterer having a resonant frequency and coupled to a side of the plate. The at least one acoustic scatterer has an opening, a first channel and a second channel. The first channel has a first channel open end and a first channel terminal end with the first channel open end being in fluid communication with the opening. The second channel has a second channel open end and a second channel terminal end with the second channel open end being in fluid communication with the opening. The first channel terminal end and the second channel terminal end are separate from one another.

An acoustic structure includes a plate and at least one acoustic scatterer having a resonant frequency and coupled to a side of the plate. The at least one acoustic scatterer has an opening, a first channel and a second channel. The first channel has a first channel open end and a first channel terminal end with the first channel open end being in fluid communication with the opening. The second channel has a second channel open end and a second channel terminal end with the second channel open end being in fluid communication with the opening. The first channel terminal end and the second channel terminal end are separate from one another.

A versatile metamaterial reflector is constructed of at least one pair of first and second reflectors each having a frequency-dependent phase shifting of a reflected waveform but together providing, between them, a constant phase difference. As few as two different types of reflectors (for example, a zero and relative pi radian reflector) are used to construct a variety of metamaterial reflectors.

There is provided an acoustically treated landing gear door for reducing noise from a landing gear of an aircraft. The acoustically treated landing gear door includes a landing gear door for attachment to the aircraft. The landing gear door includes an acoustic treatment assembly integrated on an inner mold line of an interior side, and extending within an interior cavity of the landing gear door. The acoustic treatment assembly includes a core structure having a first side and a second side, a plurality of core cells extending between the first side and the second side, and a drainage system. The acoustic treatment assembly further includes an acoustic facesheet and a nonporous backsheet. The acoustically treated landing gear door reduces the noise from the landing gear, when the landing gear is in a deployed position, by attenuating acoustic waves emanating from the landing gear and reflected off the acoustic treatment assembly.

There is provided an acoustically treated landing gear door for reducing noise from a landing gear of an aircraft. The acoustically treated landing gear door includes a landing gear door for attachment to the aircraft. The landing gear door includes an acoustic treatment assembly integrated on an inner mold line of an interior side, and extending within an interior cavity of the landing gear door. The acoustic treatment assembly includes a core structure having a first side and a second side, a plurality of core cells extending between the first side and the second side, and a drainage system. The acoustic treatment assembly further includes an acoustic facesheet and a nonporous backsheet. The acoustically treated landing gear door reduces the noise from the landing gear, when the landing gear is in a deployed position, by attenuating acoustic waves emanating from the landing gear and reflected off the acoustic treatment assembly.

Embodiments for one-way sound absorbing systems are described herein. In one example, a sound absorbing system includes a waveguide having open ends for receiving an incoming acoustic wave and wall portions defining a first port and a second port. A first electroacoustic absorber is mounted to the first port and is electrically connected to a shunting circuit, while a second electroacoustic absorber is mounted to the second port and is electrically connected to an open circuit. The sound absorption of the system is directional dependent.