Title:
Apparatuses And Methods For Sound Absorption Using Hollow Beads Loosely Contained In An Enclosure

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Abstract
A sound absorption device in accordance with this invention includes an enclosure loosely containing hollow beads. Preferably, the hollow beads have openings, and differ with respect to the volume of the hollow space defined by the walls of the beads, the wall thicknesses of the beads, the size of the openings of the beads and/or the number of openings on the beads. Through Helmholtz resonance, vorticity and tortuous path scattering, the beads damp sound waves over a broad range of frequencies. Preferably, the beads are formed from a material able to withstand relatively high temperatures, such as ceramic or nickel. The beads can thus be used to damp sound in applications which generate significant heat in addition to sound, such as aircraft engines, rocket motors or other loud, heat-generating sources, for example. Also, by forming the beads from a material with a relatively low thermal conductivity, the beads can also be used for thermal insulation in addition to sound absorption.
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7/7/1998
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