초록 ▼

An active acoustic wall has sound-pressure detectors provided within respective cells so that a detected signal acts to oscillate an oscillation plate in the cell. A porous material on a surface is thereby provided with a high sound absorption coefficient over a wide frequency range. A space between

An active acoustic wall has sound-pressure detectors provided within respective cells so that a detected signal acts to oscillate an oscillation plate in the cell. A porous material on a surface is thereby provided with a high sound absorption coefficient over a wide frequency range. A space between a porous material or a perforated plate 1 on the surface and a back material fixed on a back side is divided into a plurality of sections so as to form cells 10 containing an air layer or a porous sound-absorbing material. Oscillation plates 6 are arranged within respective cells 10 so as to be driven for oscillation by oscillation-plate driving units 5. Sound-pressure detectors 7 are provided close to the porous material 1 in the cell 10 so that a detected signal is inputted to a signal-processing unit 8. The signal processing unit 8 outputs a signal to the driving unit 5 for oscillating the oscillation plate 6 such that an output of the sound-pressure detector is minimized. The sound pressure on the surface of the porous material 1 is minimized at all frequencies. The velocity of particles on the surface becomes large so that the particles are turned into thermal energy, thereby providing a high sound-absorption coefficient.

대표청구항 ▼

[ What is claimed is:] [1.] An active acoustic wall for absorbing sound waves across a broadband frequency range, comprising:a perforated plate comprising at least one selected from the group consisting of a perforated member and a porous material, said perforated plate having a front side and a bac

[ What is claimed is:] [1.] An active acoustic wall for absorbing sound waves across a broadband frequency range, comprising:a perforated plate comprising at least one selected from the group consisting of a perforated member and a porous material, said perforated plate having a front side and a back side;a back wall spaced from said back side of said perforated plate such that a space is formed between said back side of said perforated plate and said back wall;a plurality of partition plates dividing said space between said perforated plate and said back wall into a plurality of sections;oscillation plates provided within each of said sections, respectively;driving units for driving said oscillation plates;two sound pressure detectors provided within each of said sections providing first and second signals; anda signal processing unit connected with said sound pressure detectors and said driving units, receiving each of said first and second signals, calculating the impedance of each of said sections, comparing the impedance to a predetermined value, and providing an output signal to each of said driving units such that each of said oscillation plates oscillates and creates an impedance which approximates said predetermined value.