Airborne acoustic absorber
AssigneeToyota Motor Engineering & Manufacturing North America, Inc.
InventorsTaehwa Lee, Hideo Iizuka
Life of this patent
Estimating the term…
Abstract
Airborne acoustic absorbers include periodic arrays of Helmholtz resonators that are covered and/or partially filled with an acoustically absorptive material, such as a thermoplastic foam. The combined structures have much broader frequency ranges of high acoustic absorption than do structures having only Helmholtz resonators or acoustically absorbing foam.
Claims13
An airborne acoustic absorber having an absorption frequency range, airborne acoustic the absorber comprising:
- a periodic array of unit cells, each unit cell comprising:
- a Helmholtz resonator having a resonant frequency, each Helmholtz resonator comprising:
- a chamber portion bounded by at least one enclosure wall defining a chamber volume;
- and
- a neck, forming an aperture in the at least one enclosure wall, and defining an opening to the chamber portion;
- and
- an acoustically absorbing medium overlaying the neck and contiguously filling at least a portion of the neck, thereby increasing the resonant frequency bandwidth to achieve the absorption frequency range, the acoustically absorbing medium having a porosity greater than 0.9, the acoustically absorbing medium having a thickness that is less than a wavelength corresponding to the resonance frequency of the airborne acoustic absorber,
- the airborne acoustic absorber having acoustic absorption of at least about 1.
A multi-resonance airborne acoustic absorber comprising a periodic array of unit cells, each unit cell comprising:
- a first Helmholtz resonator having:
- a first chamber portion bounded by at least one first enclosure wall defining a first chamber volume;
- and
- a first neck forming an aperture in the at least one first enclosure wall;
- and
- a second Helmholtz resonator having:
- a second chamber portion bounded by at least one second enclosure wall defining a second chamber volume;
- and
- a second neck forming an aperture in the at least one second enclosure wall;
- and
- an acoustically absorbing medium overlaying at least the first and second necks and contiguously filling at least a portion of the first and second necks, the acoustically absorbing medium having a porosity greater than 0.9, the acoustically absorbing medium having a thickness that is less than a wavelength corresponding to the resonance frequency of the multi-resonance airborne acoustic absorber,
- the multi-resonance airborne acoustic absorber having acoustic absorption of at least about 1.
A highway sound barrier comprising:
- a substantially planar or curved substrate, the substantially planar or curved substrate being a highway sound barrier;
- and
- an airborne acoustic absorber coating a surface of the substantially planar or curved substrate, the airborne acoustic absorber comprising:
- a periodic array of unit cells, each unit cell comprising a first Helmholtz resonator having a resonant frequency, each first Helmholtz resonator of the periodic array comprising:
- a first chamber portion bounded by at least one enclosure wall defining a first chamber volume;
- and
- a first neck, forming an aperture in the at least one enclosure wall, and defining an opening to the first chamber portion;
- and
- an acoustically absorbing medium overlaying the first neck and contiguously filling at least a portion of the first neck, thereby producing an absorption frequency greater than the resonant frequency, the acoustically absorbing medium having a porosity greater than 0.9, the acoustically absorbing medium having a thickness that is less than a wavelength corresponding to the resonance frequency of the airborne acoustic absorber,
- the airborne acoustic absorber having acoustic absorption of at least about 1.
Dependencies are inferred from the claim text.