Airborne acoustic absorber
AssigneeToyota Motor Engineering & Manufacturing North America, Inc.
InventorsTaehwa Lee, Hideo Iizuka
Life of this patent
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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.
Claims18
An airborne acoustic absorber having an absorption frequency range, 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, thereby increasing the resonant frequency bandwidth to achieve the absorption frequency range.
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 wherein the first and second chamber volumes are different.
A highway sound barrier comprising:
- a substantially planar or curved substrate;
- and
- an airborne acoustic absorber coating a surface of the substrate, the 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 neck, thereby producing an absorption frequency greater than the resonant frequency.
Dependencies are inferred from the claim text.