초록 ▼

A method is employed to attenuate ultrasonic noise propagating in a flow stream of a fluid flow system. In particular, the method attenuates the noise propagating between a noise source and a reference point in the flow stream (wherein the reference point and the noise source are positioned in the f

A method is employed to attenuate ultrasonic noise propagating in a flow stream of a fluid flow system. In particular, the method attenuates the noise propagating between a noise source and a reference point in the flow stream (wherein the reference point and the noise source are positioned in the flow stream in direct acoustic line of sight relation). The method includes positioning an absorbent element in the flow stream between the noise source and the reference point. Then, the ultrasonic noise is directed past vicinity of the absorbent element such that indirect ultrasonic noise is absorbed by the absorbent element. Preferably, the method also includes deflecting the ultrasonic noise to convert direct noise to indirect noise prior to directing the ultrasonic noise past the vicinity of the absorbent material in the flow stream. Such a method may be employed to attenuate ultrasonic noise by up to about 20 dB to 45 dB.

대표청구항 ▼

What is claimed is: 1. A fluid flow system comprising: a fluid flow conduit; a noise source disposed in said fluid flow conduit such that ultrasonic noise generated by said noise source propagates in said fluid flow conduit; and an ultrasonic noise filter apparatus disposed in said fluid flow condu

What is claimed is: 1. A fluid flow system comprising: a fluid flow conduit; a noise source disposed in said fluid flow conduit such that ultrasonic noise generated by said noise source propagates in said fluid flow conduit; and an ultrasonic noise filter apparatus disposed in said fluid flow conduit, said noise filter apparatus including a first noise filter and a second noise filter; wherein said first noise filter includes an absorbent element constructed to attenuate ultrasonic noise propagating from said noise source in the direction of said first and second noise filters; and wherein said second noise filter is disposed in said fluid flow conduit between said first noise filter and said noise source and includes a deflector element positioned to deflect ultrasonic noise propagating from said noise source before the noise source passes to said first noise filter. 2. The fluid flow system of claim 1, wherein said deflector element is acoustically positioned in said fluid flow conduit so as to provide the sole direct line of sight acoustic obstruction between said noise source and said first and second noise filters. 3. The fluid flow system of claim 2, wherein said second noise filter includes a plurality of said deflector elements, said deflector element having a configuration defining a flow path with an entrance and an exit, and wherein said entrance and said exit are offset to eliminate direct line of sight therebetween. 4. The fluid flow system of claim 1, wherein said second noise filter includes a plurality of said deflector elements, said deflector elements having a configuration defining a flow path with an entrance and an exit, wherein said entrance and said exit are offset to eliminate direct line of sight therebetween and wherein said deflector elements are positioned such that, in a plurality of deflector elements, each deflector element rotated in one direction is positioned adjacent a deflector element rotated in a counter direction. 5. The fluid flow system of claim 1, further comprising: an ultrasonic device operable at ultrasonic frequencies, said ultrasonic device being disposed in said fluid flow conduit such that said first and second noise filters are positioned intermediate said ultrasonic device and said noise source. 6. The fluid flow system of claim 5, wherein said second noise filter is acoustically positioned in said fluid flow conduit so as to provide the sole direct line of sight obstruction between said noise source and said ultrasonic device. 7. The fluid flow system of claim 5, wherein said noise source is a control valve and said ultrasonic device is an ultrasonic meter. 8. The fluid flow system of claim 7, wherein said meter, said noise filter apparatus, and said control valve define a substantially straight flow stream thereacross. 9. The fluid flow system of claim 1, wherein said deflector element is configured to convert directly propagating noise to indirectly propagating noise. 10. The fluid flow system of claim 1, wherein said absorbent element includes an absorbent material configured to convert ultrasonic acoustic motion to vibration, thereby attenuating ultrasonic noise. 11. The fluid flow system of claim 10, wherein said fluid flow conduit defines a fluid flow stream and wherein said absorbent material is disposed in generally parallel relation with said flow stream. 12. The fluid flow system of claim 11, wherein said absorbent material includes suspended, vibratable members of said absorbent material positioned into said flow stream. 13. The fluid flow system of claim 10, wherein said absorbent material is a fibrous material. 14. The fluid flow system of claim 10, wherein said absorbent element includes lateral sections formed by spirally wound layers of said absorbent material. 15. The fluid flow system of claim 14, wherein said fluid flow conduit defines a fluid flow stream and wherein said lateral sections overlap to form protrusions into said flow stream. 16. The fluid flow system of claim 14, wherein said lateral sections include pairs of said spirally wound layers of absorbent material that are adjacent one another and disposed in opposite spiral wound relation. 17. The fluid flow system of claim 10, wherein said absorbent material is polyester. 18. The fluid flow system of claim 1, wherein said first noise filter includes a plurality of channels each defining a flow path, and an absorbent wall surface positioned in generally parallel relation with said flow path and whereon absorbent material of said absorbent element is disposed. 19. The fluid flow system of claim 18, wherein said first noise filter includes a longitudinal centerline and a plurality of outside channels positioned radially equidistant from said longitudinal centerline. 20. The fluid flow system of claim 19, wherein said first noise filter includes an inside channel positioned about said longitudinal centerline, said inside channel having an inside surface whereon said absorbent material is disposed. 21. The fluid flow system of claim 19, wherein said outside channels include an absorbent wall surface whereon said absorbent material is disposed and an oppositely facing exposed surface free of said absorbent material, said absorbent and exposed wall surfaces defining a maximum gap therebetween. 22. The fluid flow system of claim 21, wherein said outside channel includes an entrance, said entrance including a lip positioned acoustically upstream of and adjacent said absorbent wall surface, such that a maximum gap between said lip and said exposed surface is less than said maximum gap between said absorbent wall surface and said exposed wall surface, and wherein said lip is adapted to generate turbulent flow immediately downstream thereof.