Passive directional acoustic radiating

Abstract

An audio system for a television using a pipe type passive directional acoustic device mounted in a television cabinet. The slotted pipe type passive directional acoustic device includes a first acoustic driver, acoustically coupled to a pipe to radiate acoustic energy into the pipe. The first pipe includes an elongated opening along at least a portion of the length of the pipe. Acoustically resistive material is in the opening. Pressure waves are radiated to the environment through the opening. The pressure waves are characterized by a volume velocity. The pipe, the opening, and the acoustically resistive material are configured so that the volume velocity is substantially constant along the length of the pipe. The passive directional acoustic devices directionally radiate sound waves laterally from the television cabinet.

What is claimed is: 
     
       1. An audio system for a television comprising:
 a television cabinet;   a first slotted pipe type passive directional acoustic device comprising   a first acoustic driver, acoustically coupled to a pipe to radiate acoustic energy into the pipe,   the first pipe comprising   an elongated opening along at least a portion of the length of the pipe; and   acoustically resistive material in the opening through which pressure waves are radiated to the environment,   the pressure waves characterized by a volume velocity, the pipe, the opening, and the acoustically resistive material configured so that the volume velocity of the pressure waves radiated to the environment from the pipe is substantially constant along the length of the pipe; and   
       wherein the passive directional acoustic device is mounted in the television cabinet to directionally radiate sound waves laterally from the television cabinet. 
     
     
       2. The audio system for a television of  claim 1 , wherein the pipe is at least one of bent or curved. 
     
     
       3. The audio system for a television of  claim 2  wherein the opening is at least one of bent or curved along its length. 
     
     
       4. The slotted pipe type passive directional acoustic device of  claim 2 , wherein the opening is in a face that is bent or curved. 
     
     
       5. The audio system for a television of  claim 2 , wherein the television cabinet is tapered backwardly, and wherein the passive directional acoustic device is mounted so that a curved or bent wall of the slotted pipe type passive directional acoustic device is substantially parallel to the back and a side wall of the television cabinet. 
     
     
       6. The audio system for a television of  claim 2 , wherein the opening comprises two sections, a first section in a top face of the pipe and a second section in a side face of the pipe. 
     
     
       7. The audio system for a television of  claim 1 , wherein the passive directional acoustic device is for radiating the high frequency content of a left channel or a right channel laterally from the television. 
     
     
       8. The audio system for a television of  claim 7 , wherein the acoustic device is for radiating the left channel or right channel content above 2 kHz. 
     
     
       9. The audio system for a television of  claim 7 , further comprising a directional array for radiating midrange frequency content of the left channel or right channel laterally from the television. 
     
     
       10. The audio system for a television of  claim 9 , further comprising a waveguide structure for radiating bass frequency content of
 the left channel or right channel;   the other of the left channel or right channel; and   a center channel.   
     
     
       11. The audio system of  claim 1 , wherein the cross sectional area of the pipe decreases along the length of the pipe. 
     
     
       12. The audio system of  claim 1 , further comprising a second slotted pipe type passive directional acoustic device comprising
 a second acoustic driver, acoustically coupled to a pipe to radiate acoustic energy into the pipe,   the second pipe comprising   an elongated opening along at least a portion of the length of the pipe; and   acoustically resistive material in the opening through which pressure waves are radiated to the environment,   the pressure waves characterized by a volume velocity, the pipe, the opening, and the acoustically resistive material configured so that the volume velocity is substantially constant along the length of the pipe; and   
       wherein the first passive directional acoustic device is mounted in the television cabinet to directionally radiate sound waves laterally leftward from the television cabinet and the second passive radiator is mounted in the television cabinet to directionally radiate sound waves laterally rightward from the television cabinet. 
     
     
       13. An acoustic apparatus, comprising:
 an acoustic driver, acoustically coupled to a first location in a passive directional device to radiate acoustic energy into the passive directional device,   the passive directional device comprising an opening in the perimeter of the passive directional device, the opening extending along at least a portion of a length of the passive directional device through which acoustic energy is radiated to an environment, the opening characterized by an opening area, wherein the opening area is covered by an acoustically resistive material, wherein the opening area varies as a function of the length of the passive directional device such that the opening area over a first portion of the opening closer to the location of the acoustic driver increases with increasing distance from the acoustic driver, and the area of the opening, over a second portion of the opening farther away from the acoustic driver than the first portion, decreases with increasing distance from the acoustic driver,   wherein the opening has an acoustical resistance,   wherein the acoustical resistance of the opening varies with distance from the acoustic driver along the passive directional device, and   wherein substantially all of the acoustic energy radiated into the passive directional device by the acoustic driver exits the passive directional device through the opening or is dissipated in the acoustical resistance of the opening, prior to the acoustic energy reaching an end of the passive directional device that is disposed away from the first location.   
     
     
       14. The acoustic apparatus of claim 13 wherein the cross-sectional area of the passive directional device decreases with distance from the acoustic driver. 
     
     
       15. The acoustic apparatus of claim 13 wherein the opening in the perimeter of the passive directional device extends along substantially the length of the passive directional device. 
     
     
       16. The acoustic apparatus of claim 13 wherein the opening in the perimeter of the passive directional device is non-rectangular. 
     
     
       17. The acoustic apparatus of claim 13 wherein the opening in the perimeter of the passive directional device lies in a plane that intersects the passive directional device at a non-zero, non-perpendicular angle relative to a central axis of the passive directional device. 
     
     
       18. The acoustic apparatus of claim 13 wherein acoustically resistive material is located in the opening to provide acoustical resistance. 
     
     
       19. The acoustic apparatus of claim 18 wherein the total acoustical resistance of the acoustically resistive material combined with the acoustical resistance of the opening varies along the length of the passive directional device. 
     
     
       20. The acoustic apparatus of claim 18 wherein the acoustically resistive material is at least one of the group consisting of: wire mesh, felt, sintered plastic, woven fabric, and unwoven fabric. 
     
     
       21. The acoustic apparatus of claim 13 wherein the cross-sectional area of the passive directional device, normal to a central axis of the passive directional device, varies along the length of the passive directional device. 
     
     
       22. An acoustic apparatus, comprising:
 an acoustic driver, acoustically coupled to a first location in a passive directional device to radiate acoustic energy into the passive directional device,   wherein the cross sectional area of the passive directional device, normal to a central axis of the passive directional device, varies along the length of the passive directional device,   the passive directional device comprising an opening in the perimeter of the passive directional device extending along substantially the length of the passive directional device through which acoustic energy is radiated to the environment, the opening characterized by an opening area, wherein the opening area is covered by an acoustically resistive material,   wherein the opening area varies as a function of the length of the passive directional device such that the opening area over a first portion of the opening closer to the location of the acoustic driver increases with increasing distance from the acoustic driver, and the area of the opening, over a second portion of the opening farther away from the acoustic driver than the first portion, decreases with increasing distance from the acoustic driver,   wherein the opening has an acoustical resistance, and   wherein substantially all of the acoustic energy radiated into the passive directional device by the acoustic driver exits the passive directional device through the opening or is dissipated in the acoustical resistance of the opening, prior to the acoustic energy reaching an end of the passive directional device that is disposed away from the first location.   
     
     
       23. The acoustic apparatus of claim 22 wherein the opening in the perimeter of the passive directional device is non-rectangular. 
     
     
       24. The acoustic apparatus of claim 22 wherein the opening in the perimeter of the passive directional device lies in a plane that intersects the passive directional device at a non-zero, non-perpendicular angle relative to a central axis of the passive directional device. 
     
     
       25. The acoustic apparatus of claim 22 wherein acoustically resistive material is located in the opening to provide acoustical resistance. 
     
     
       26. The acoustic apparatus of claim 25 wherein the total acoustical resistance of the acoustically resistive material combined with the acoustical resistance of the opening varies along the length of the passive directional device. 
     
     
       27. The acoustic apparatus of claim 25 wherein the acoustically resistive material is at least one of the group consisting of: wire mesh, felt, sintered plastic, woven fabric, and unwoven fabric. 
     
     
       28. The acoustic apparatus of claim 22 wherein the cross-sectional area of the passive directional device decreases with distance from the acoustic driver. 
     
     
       29. A method for directionally radiating sound, comprising:
 radiating acoustic energy into a passive directional device by an acoustic driver coupled to a first location in the passive directional device,   wherein the cross-sectional area of the passive directional device, normal to a central axis of the passive directional device, varies along the length of the passive directional device,   wherein the passive directional device comprises an opening in the perimeter of the passive directional device extending along substantially the length of the passive directional device through which acoustic energy is radiated to the environment, the opening characterized by an opening area, wherein the opening area is covered by an acoustically resistive material,   wherein the opening area varies as a function of the length of the passive directional device such that the opening area over a first portion of the opening closer to the location of the acoustic driver increases with increasing distance from the acoustic driver, and the area of the opening, over a second portion of the opening farther away from the acoustic driver than the first portion, decreases with increasing distance from the acoustic driver,   wherein the opening has an acoustical resistance,   radiating acoustic energy so as to exit through the opening in the passive directional device, and;   dissipating acoustic energy in the acoustical resistance of the opening, wherein substantially all of the acoustic energy radiated into the passive directional device either exits through the opening in the passive directional device or is dissipated in the acoustical resistance of the opening, prior to the acoustic energy reaching an end of the passive directional device that is disposed away from the first location.   
     
     
       30. The method for directionally radiating sound of claim 29 wherein the opening in the perimeter of the passive directional device is non-rectangular. 
     
     
       31. The method for directionally radiating sound of claim 29 wherein the opening in the perimeter of the passive directional device lies in a plane that intersects the passive directional device at a non-zero, non-perpendicular angle relative to a central axis of the passive directional device. 
     
     
       32. The method for directionally radiating sound of claim 29 wherein acoustically resistive material is located in the opening to provide acoustical resistance. 
     
     
       33. The method for directionally radiating sound of claim 32 wherein the total acoustical resistance of the acoustically resistive material combined with the acoustical resistance of the opening varies along the length of the passive directional device. 
     
     
       34. The method for directionally radiating sound of claim 32 wherein the acoustically resistive material is at least one of the group consisting of: wire mesh, felt, sintered plastic, woven fabric, and unwoven fabric. 
     
     
       35. The method for directionally radiating sound of claim 29 wherein the cross-sectional area of the passive directional device decreases with distance from the acoustic driver.