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Low Cost Quarter Wave Resonator for Acoustic Tone Reduction Disclosure Number: IPCOM000016315D
Original Publication Date: 2002-Nov-17
Included in the Prior Art Database: 2003-Jun-21

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This disclosure describes a low cost fabrication technique for a quarter wave resonator. Quarter wave resonators have been well documented and when properly engineered, can reduce acoustic noise at specific frequencies. Most resonators documented in prior art require expensive injection molding or sheet forming fabrication tools. This disclosure documents a fabrication method that results in a very low cost resonator. The subject resonator is made from material commonly known in the distribution packaging industry as "corrugated polypropylene board" or "corrugated polyethylene board". The material is extruded with a plurality of parallel ducts intended to give the board rigidity for the packaging containers. When one end of the duct is sealed by thermal welding or the application of sealing tape, and the length is cut to 1/4 the wave length of acoustic noise to be attenuated, the corrugated board will function as a quarter wave resonator to attenuate noise at specific frequencies when placed inside a passageway transmitting sound. The resulting resonator requires very little tooling cost, has low material cost, the material is readily available, it can be fabricated or modified very quickly, and is very compact and space efficient. The following sketch shows a resonator tuned to 1433 Hz at sea level. 6 mm