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.

Description

FIELD OF THE INVENTION [0001] The present invention relates to motor vehicles and, in particular, to acoustical insulation for use on interior and exterior surfaces of the passenger compartment of motor vehicles. BACKGROUND OF THE INVENTION [0002] Sound attenuating materials are provided for acoustically insulating motor vehicles to reduce the level of noise inside the vehicle passenger compartment. External noises, such as road noise, wind noise, engine noise, vibrations, etc. may be attenuated through the use of various acoustical materials applied to the internal and external surfaces of the passenger compartment. Noises emanating from sources within the passenger compartment may be attenuated through the use of various acoustical materials applied to the internal surfaces of the passenger compartment. [0003] The attenuation of airborne noise from external sources transmitted through the body structure and components to the passenger compartment is commonly referred to as sound t...

AI Technical Summary

Benefits of technology

[0008] The invention therefore provides a sound attenuating material that includes a layer of nonwoven material and an underlying layer supporting the single cap layer. This simple two-layer structure provides acoustical attenuation effective to significantly reduce the audibility of common externally-originated noises, such as road noise and engine noise. In comparison with conventional barrier type acoustical insulators, the layered acoustical insulator of the present invention is realized with substantial cost savings and a lightweight construction. The acoustical insulator is biased toward providing sound absorption rather than sound transmission loss as the mechanism for acoustical attenuation because of the construction of the cap layer, which represents a benefit in comparison with conventional acoustical insulators used to sonically insulate the passenger cabin in motor vehicles.

Problems solved by technology

These molded barrier mats are designed to have high transmission loss.

Increasing the areal mass of the barrier mat and the thickness of the fiber-foam layer increases the transmission loss.

Generally, these dual layer sound insulating materials are designed to provide high sound transmission loss at the expense of the sound absorption, which is low because the barrier mat is impermeable.

Phenolic resins are undesirable due to the presence of formaldehyde and odors, as well as the need to utilize a high-tonnage press to manufacture a shaped product.

Generally, such single layer sound insulating materials are not optimized for sound absorption and transmission loss.

However, these are complex structures that require multiple process steps to successfully form into a shaped component.

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