Acoustical insulation for motor vehicles

Abstract

Acoustical insulation for attenuating sound entering the passenger compartment of motor vehicles. The acoustical insulator comprises dual nonwoven layers in which one nonwoven layer is an airflow control layer and the second nonwoven layer is a support layer positioned between the cap layer and the sheet metal of the firewall separating the passenger and engine compartments. The areal density of the cap layer is less than the areal density of the support layer and, preferably, comprises polyethylene terephthalate (PET) fibers. The cap layer has a specific airflow resistance ranging from about 200 mks Rayls to about 1200 mks Rayls.

1 . An acoustical insulator for application to an interior surface of a motor vehicle, comprising: 
 a first nonwoven layer having a first areal density; and    a second nonwoven layer coupled with said first nonwoven layer to define a laminate, said second nonwoven layer having a second areal density less than said first areal density, said laminate adapted to be applied to the interior surface of the motor vehicle with said first nonwoven layer being positioned between said second nonwoven layer and the surface, and said second nonwoven layer having a specific airflow resistance between about 200 mks Rayls and about 1200 mks Rayls.    
     
     
         2 . The acoustical insulator of  claim 1  wherein the specific airflow resistance of said second nonwoven layer is within a range from about 200 mks Rayls to about 1200 mks Rayls.  
     
     
         3 . The acoustical insulator of  claim 1  wherein said second nonwoven layer has a thickness less than 1.5 mm.  
     
     
         4 . The acoustical insulator of  claim 3  wherein said laminate has a thickness ranging from about 4 mm to 37 mm.  
     
     
         5 . The acoustical insulator of  claim 1  wherein said second nonwoven layer has an areal density ranging from about 5 grams·ft −2 to about 25 grams·ft −2 .  
     
     
         6 . The acoustical insulator of  claim 1  wherein said first nonwoven layer has an areal density ranging from about 80 grams·ft −2  to about 150 grams·ft −2 .  
     
     
         7 . The acoustical insulator of  claim 1  wherein said second nonwoven layer is a lofted fibrous layer compressed to a thickness less than 1.5 mm before part molding.  
     
     
         8 . The acoustical insulator of  claim 1  wherein said second nonwoven layer includes a plurality of first fibers each formed from polyethylene terephthalate (PET) and a plurality of second fibers each formed from a binder fiber.  
     
     
         9 . The acoustical insulator of  claim 1  wherein said second nonwoven layer is bonded to the first non-woven layer by the pressure of a molding process.  
     
     
         10 . The acoustical insulator of  claim 1  wherein said first nonwoven layer contacts the interior surface when said acoustical insulator is applied to the interior surface.  
     
     
         11 . The acoustical insulator of  claim 1  wherein said first nonwoven layer comprises cross-lapped cotton fibers.  
     
     
         12 . The acoustical insulator of  claim 11  wherein said first nonwoven layer further comprises polyester fibers blended with the cotton fibers.  
     
     
         13 . The acoustical insulator of  claim 1  wherein said first nonwoven layer comprises cross-lapped polyester fibers.  
     
     
         14 . The acoustical insulator of  claim 13  wherein said first nonwoven layer further comprises binder fibers blended with said polyester fibers.