Excitation of air directing valves and air handling surfaces in the cancellation of air handling system noise

Abstract

A piezoelectric vibrator generates attenuating waves in an air duct in an automobile HVAC system to cancel or reduce the noise created by sound waves. A processor converts a sinusoidal noise signal into an attenuation signal, which is the additive inverse of the sinusoidal noise signal. The processor may include an inverter or a phase-shifter to create the attenuation signal, as well as an amplifier to adjust the amplitude of the attenuation signal. The attenuation signal drives the piezoelectric vibrator.

1 . A system for reducing noise in an air flow structure comprising; 
 an air duct defining an air flow passage for conveying an air flow having sound waves therein,    a sensor in said air duct for sensing the sound waves and producing a noise signal in response to the sound waves in said air duct,    a driver supported in said air duct and responsive to the noise signal for vibrating in said air duct to attenuate the sound waves in said duct, and    said driver including a piezoelectric vibrator.    
   
   
       2 . The system as set forth in  claim 1  further comprising a processor electrically connected between said sensor and said driver and responsive to the noise signal for producing an attenuation signal to vibrate said piezoelectric vibrator to produce attenuating waves in opposition to the sound waves.  
   
   
       3 . The system as set forth in  claim 2  wherein said processor includes an amplifier for amplifying the noise signal.  
   
   
       4 . The system as set forth in  claim 2  wherein said sensor includes a noise signal that is sinusoidal and said processor includes a phase-shifter for shifting a phase of the sinusoidal noise signal.  
   
   
       5 . The system as set forth in  claim 2  wherein said sensor includes a noise signal that is sinusoidal and said processor includes an inverter for inverting the sinusoidal noise signal.  
   
   
       6 . The system as set forth in  claim 1  wherein said air duct includes a wall and said piezoelectric vibrator is supported on said wall.  
   
   
       7 . The system as set forth in  claim 6  wherein said wall includes an opening and said piezoelectric vibrator is disposed over said opening.  
   
   
       8 . The system as set forth in  claim 7  wherein said wall comprises a plastic and said piezoelectric vibrator is a film having edges secured to said wall about said opening.  
   
   
       9 . The system as set forth in  claim 7  wherein said wall is movably supported in said air duct for regulating the air flow through said air duct.  
   
   
       10 . The system as set forth in  claim 1  including a blower assembly for moving air through said air duct and producing the sound waves in said air duct to be attenuated by said piezoelectric vibrator.