Gas flow sound attenuation device

Abstract

The gas flow sound attenuation device includes a number of variations each having at least one pressure pulse reflecting chamber, i.e., a Helmholtz chamber, installed in axial alignment with the upstream gas flow. Gas flow is transferred laterally externally to the chamber, with the single opening of the chamber receiving substantially all incoming pressure pulse energy to maximize the reflection and canceling of those pulses back into the upstream duct. The device may incorporate any practicable number of chambers, so long as each has at least some length of upstream pipe or duct axially aligned with the chamber opening. The chambers may have any practicable shape and/or may include internal baffling. The device may be applied to any gas flow system, e.g., heating, ventilation, and air conditioning systems, but is particularly effective in reducing the sound output of internal combustion engine exhaust systems.

1 . A gas flow sound attenuation device, comprising:
 at least one elongate gas flow passageway having:
 an inlet end; 
 an outlet end opposite the inlet end; 
 at least one upstream portion disposed between the inlet end and the outlet end; 
 a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; and 
 at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and 
   a sound-canceling chamber having a single opening defined therein, the single opening connected to and communicating with the outlet end of the stub portion and in axial alignment therewith.   
   
   
       2 . The gas flow sound attenuation device according to  claim 1 , wherein said at least one elongate passageway comprises an exhaust gas flow passageway and said sound canceling chamber comprises an exhaust sound canceling chamber. 
   
   
       3 . The gas flow sound attenuation device according to  claim 1 , wherein said at least one elongate gas flow passageway comprises a plurality of elongate gas flow passageways and said sound canceling chamber comprises a plurality of chambers, each of the chambers being connected to a corresponding one of the gas flow passageways. 
   
   
       4 . The gas flow sound attenuation device according to  claim 3 , further including an external shell surrounding all of the gas flow passageways and sound canceling chambers, the shell having an inlet and an outlet communicating with the gas flow passageways. 
   
   
       5 . The gas flow sound attenuation device according to  claim 1 , wherein said sound canceling chamber has a plurality of branches. 
   
   
       6 . The gas flow sound attenuation device according to  claim 1 , wherein said sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the single opening defined therein. 
   
   
       7 . The gas flow sound attenuation device according to  claim 1 , wherein said sound canceling chamber has a polyhedral external configuration. 
   
   
       8 . The gas flow sound attenuation device according to  claim 1 , wherein said sound canceling chamber has at least one internal baffle disposed therein. 
   
   
       9 . An internal combustion engine exhaust gas flow sound attenuation device, comprising:
 at least one elongate exhaust gas flow passageway having:
 an inlet end; 
 an outlet end opposite the inlet end; 
 at least one upstream portion disposed between the inlet end and the outlet end; 
 a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; and 
 at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and 
   an exhaust sound-canceling chamber having a single opening defined therein, the single opening connected to and communicating with the outlet end of the stub portion and in axial alignment therewith.   
   
   
       10 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 9 , wherein said at least one elongate exhaust gas flow passageway comprises a plurality of elongate exhaust gas flow passageways and said exhaust sound canceling chamber comprises a plurality of chambers, each of the chambers being connected to a corresponding one of the exhaust gas flow passageways. 
   
   
       11 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 10 , further including an external shell surrounding all of the exhaust gas flow passageways and exhaust sound canceling chambers, the shell further having an inlet and an outlet each communicating with the exhaust gas flow passageways. 
   
   
       12 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 9 , wherein said exhaust sound canceling chamber has a plurality of branches. 
   
   
       13 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 9 , wherein said exhaust sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the opening thereof. 
   
   
       14 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 9 , wherein said exhaust sound canceling chamber has a polyhedral external configuration. 
   
   
       15 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 9 , wherein said exhaust sound canceling chamber has at least one internal baffle disposed therein. 
   
   
       16 . An internal combustion engine exhaust gas flow sound attenuation device, comprising:
 a plurality of elongate gas flow passageways, each of the passageways having:
 an inlet end; 
 an outlet end opposite the inlet end; 
 at least one upstream portion disposed between the inlet end and the outlet end; 
 a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; 
 at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and 
 an exhaust sound canceling chamber having a single opening therein, the single opening connected to and communicating with the outlet end of each stub portion and in axial alignment therewith; and 
   an external shell surrounding all of the gas flow passageways and sound canceling chambers, the shell having an inlet and an outlet each communicating with the gas flow passageways.   
   
   
       17 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 16 , wherein at least one said exhaust sound canceling chamber has a plurality of branches. 
   
   
       18 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 16 , wherein at least one said exhaust sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the opening thereof. 
   
   
       19 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 16 , wherein at least one said exhaust sound canceling chamber has a polyhedral external configuration. 
   
   
       20 . The internal combustion engine exhaust gas flow sound attenuation device according to  claim 16 , wherein at least one said exhaust sound canceling chamber has at least one internal baffle disposed therein.