The Hong Kong University of Science and Technology

Hong Kong Baptist University

Guancong Ma

Ping Sheng

Zhiyu Yang

Min Yang

Songwen Xiao

Liang Sun

Weijia Wen

Yong Bin Li

Zhen Dong

Ho Yiu Mak

Xiaonan Zhang

Jie Pan

Suet To Tang

Jun Mei

An active sound barrier has at least one passive sound absorber at or near a boundary location. A microphone provides an output to a frequency division module, in which a plural of frequencies are filtered to provide outputs corresponding to frequency segments of the receiving transducer output at respective ones of the frequencies. An active driving circuit drives plural speakers or output transducers at respective ones of the frequencies, with at least a subset of the speakers or output transducers at or close to the barrier. The speakers or output transducers cooperate with the passive sound absorber to reduce noise across a wide frequency band as well as to effect an electrically switchable soft boundary.

Low frequency acoustic absorption and soft boundary effect with frequency-discretized active panels

A sound absorption panel () is constructed on an acoustically thin sheet () to provide an acoustic/vibrational energy absorption metamaterial structure. A plurality of dampers () are fixed to the acoustically thin sheet (), and at least a subset of said dampers () comprise a support () and a flexible membrane () supported by the support. The flexible membrane () has one or more masses or platelets () attached. The dampers () in combination with the sheet () result in absorption of energy of movement of the sheet () resulting from sound transmission or vibrations across the sheet.

Vibration damped sound shield

A sound absorbing metamaterial comprises an acoustic impedance-matched surface configured to minimize reflection from an incident acoustic wave. The surface is comprised of an elastic or flexible membrane and a substantially rigid mass mounted on the membrane. A relatively solid surface is provided as a reflective surface and is positioned behind the membrane. The reflective surface is separated by a predetermined distance from the elastic or flexible membrane and forms a fluid space between the membrane and the solid surface. The mass mounted on the membrane, in combination with the elastic membrane establish a plurality of eigenfrequencies.

Extraordinary acoustic absorption induced by hybrid resonance and electrical energy generation from sound by hybrid resonant metasurface

Sound attenuation is performed using a sound attenuation panel using an electromagnetic or electrostatic response unit to modify resonance. The sound attenuation panel has an acoustically transparent planar, rigid frame divided into a plurality of individual cells configured for attenuating sound. In one configuration, each cell has a weight fixed to the membrane. The planar geometry of each said individual cell, the flexibility of the membrane, and the weight establish a base resonant frequency for sound attenuation. The electromagnetic or electrostatic response unit is configured to modify the resonant frequency of the cell.

Active control of membrane-type acoustic metamaterial

A substantially acoustically transparent planar, rigid frame divided into a plurality of individual, substantially two-dimensional cells is used to construct a sound absorption panel. A sheet of a flexible material is fixed to the rigid frame, and a plurality of platelets fixed to the sheet of flexible material such that each cell is provided with a respective platelet, thereby establishing a resonant frequency, establishing an increase in an absorption coefficient of the panel. The flexible material has a wrinkle or corrugation to permit distortion with reduced material elasticity. The wrinkle or corrugation permits the flexible material to distort beyond that afforded by a planar material of the same type, while retaining mechanical strength in supporting the plurality of platelets.

Acoustic and vibrational energy absorption metamaterials

A sound attenuation panel is configured with a substantially acoustically transparent planar, rigid frame divided into a plurality of individual, substantially two-dimensional cells. A sheet of a flexible material is fixed to the rigid frame, and a plurality of platelets fixed to the sheet of flexible material such that each individual cell of the plurality of cells is provided with a respective platelet to establish a resonant frequency, the resonant frequency defined by the planar geometry of the individual cells, the flexibility of the flexible material and the platelets. The cells are divided into at least two different types of the individual cells, configured so that sound waves emitted by a first type of said different types of individual cells establishes a sound cancellation pattern with sound waves emitted by a second type of said different individual cells or an aggregation of different types of the individual cells.

Sound attenuating structures

An acoustic/vibrational energy absorption metamaterial includes at least one enclosed planar frame with an elastic membrane attached having one or more rigid plates are attached. The rigid plates have asymmetric shapes, with a substantially straight edge at the attachment to said elastic membrane, so that the rigid plate establishes a cell having a predetermined mass. Vibrational motions of the structure contain a number of resonant modes with tunable resonant frequencies.

A device with simultaneous negative effective mass density and bulk modulus has at least one tubular section and front and back membranes sealing the tubular section. The front and back membranes sealing the tubular sections seal the tubular section sufficiently to establish a sealed or restricted enclosed fluid space defined by the tubular section and the membranes, and restrict escape or intake of fluid resulting from acoustic vibrations. A pair of platelets are mounted to the membranes, with the individual platelets substantially centered on respective ones of the front and back membranes.

Acoustic metamaterial with simultaneously negative effective mass density and bulk modulus

An acoustic energy absorption metamaterial includes at least one enclosed planar frame with an elastic membrane attached having one or more rigid plates are attached. The rigid plates have asymmetric shapes, with a substantially straight edge at the attachment to said elastic membrane, so that the rigid plate establishes a cell having a predetermined mass. Vibrational motions of the structure contain a number of resonant modes with tunable resonant frequencies.

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Guancong Ma