Sound attenuating box
AssigneeFraunhofer-Gesellschaft
InventorsHelmut V. Fuchs, Ulrich Ackermann, Norbert Rambausek
Life of this patent
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Abstract
The propagation of sound in flow channels is attenuated by a sound attenuating box comprised of cell-like chambers each with a bottom, an outer plate and a partition with an opening spaced from the outer plate such that the Helmholtz resonator established by the sub-chamber between the bottom and the partiton as well as by the opening is positively coupled to the outer plate as far as vibrations in the audible range are concerned through air flow through the openings and in the subchamber between partition and outer plate. The chambers share appropriately side walls, bottoms, partitions as well as aperture plates, and outer plates.
Claims26
A sound attenuator box, particularly for attenuating sound waves in an audible range propagating in flow channels, such as venting channels, and including:
- (a) at least one enclosed chamber forming, a hollow cavity and being bounded to one side by means of an outer plate excitable to undergo vibrations in the audible range;
- and
- (b) at least one inner plate which is arranged essentially parallel to the outer plate inside the hollow cavity of the chamber, and partitioning the hollow chamber into two partial first and second follow chambers, which are interconnected exclusively through a passage opening in the inner plate, said passage opening together with the first partial cavity facing away from said outer plate establishing a Helmholtz resonator tuned to osciallations in the audible frequency range;
- the improvement comprising:
- said inner plate, said first and second partial chambers, and said outer plate constituting a vibrating entity, oscillating in the audible range;
- said outer plate being of an unperforated, impermeable configuration;
- there being such a small distance (S) between said inner plate (4) and said outer plate (3), so that the vibrations of the outer plate (3) and of the Helmholtz resonator are positively coupled by means of oscillation induced air or gas currents in said second partial chamber between the outer plate (3) and the inner plate (4) as well as said passage opening (7).
A sound attenuation box comprising:
- a plurality of juxtaposed hollow chambers each having a rear wall, a bottom, side walls, an unperforated, impermeable front-outer plate means, and a partition extending between the side walls parallel to the outer plate means;
- said partition having an opening by means of which portions of the chamber as partitioned by the partition communicate;
- said partition being capable of undergoing vibrations, a portion of each chamber being defined by the partition so that the partition, the outer plate means, and a space in-between are also capable of undergoing oscillation in the audible range;
- the bottom as well as the opening being a Helmholtz resonator for frequencies in the audible range;
- and
- said partition having a spacing from the outer plate means to positively couple the Helmholtz resonator to the vibrations which the outer plate means undergo.
Dependencies are inferred from the claim text.