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  Acoustic absorber/barrier compositeRelated Patent Categories: Acoustics, Sound-modifying Means, Sound Absorbing Panels, Multilayer Panel Or Wall StructureThe Patent Description & Claims data below is from USPTO Patent Application 20060289231. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention relates to high performance lightweight acoustic attenuation materials, and more particularly to multilayered acoustic attenuation materials that are thermoformable. BACKGROUND OF THE INVENTION [0002] It is generally desirable to reduce the level of noise within a vehicle passenger compartment. External noises, such as road noise, engine noise, vibrations, etc., as well as noises emanating from within the passenger compartment, may be attenuated through the use of various acoustical materials. The attenuation of external noise is conventionally referred to as sound transmission loss (STL). The attenuation of internal noise is conventionally referred to as sound absorption. The acoustic impedance of a material is defined as material density times acoustic velocity, and is expressed in units of Rayls (Newton-seconds/meter.sup.3). Acoustic impedance defines how easy it is for air to move through a material. Thus, for fibrous materials, acoustic impedance depends upon the density of the fibrous material and fiber diameter. Generally, the heavier the blanket and the finer the fibers, the higher the acoustic impedance. Thicker layers typically have more acoustic impedance than thin layers. [0003] Conventional acoustic treatments for reducing sound transmission at a vehicle firewall which separates the passenger compartment from an engine compartment consist of an acoustic absorber such as an open-cell polyurethane foam or a resinated fiber pad which faces the firewall, and a barrier sheet such as a heavily filled thermoplastic material. [0004] Thermoformable acoustic insulating and/or sound absorbing sheet materials are employed in substantially all mass produced motorized vehicles having a weather-tight passenger compartment. Thermoformability refers to the ability of the sheet material to be shaped in a molding tool under application of heat and, optionally, pressure, and subsequently retain the molded shape. It is highly desirable that the thermoformable acoustic sheet material used for molding sound insulating and/or sound absorbing panels for motorized vehicle applications has properties that impart resilience and flexibility to the finished panels. This combination of thermoformability, flexibility and resilience or shape-retention facilitates economical installation of the acoustic panel into the vehicle by allowing the panel to be bent during installation, such as to fit the panel into an obstructed space, without damaging or permanently deforming the shape of the panel, and by ensuring that the panel will conform as precisely as needed to the contours of a vehicle component without extensive laborious manipulation of the panel. [0005] In addition to thermoformability, flexibility and resilience, all of which are important for achieving economical manufacturing and/or installation of the acoustic panel, there is a need for progressively thinner acoustic panels in order to maximize space availability for other vehicle components, passengers and cargo. Further, there is also a progressive need for lighter weight acoustic panels in order to minimize fuel consumption. [0006] While known thermoformable acoustic sheet materials have performed adequately, there nevertheless is a desire to develop improved thermoformable, acoustic attenuation sheet materials that achieve a better combination of low cost, lightweight, reduced thickness, and outstanding acoustic attenuation properties. SUMMARY OF THE INVENTION [0007] The invention is directed to lightweight, thermoformable, multilayered sheet materials that incorporate a combination of sound attenuating materials that perform various sound attenuating functions and provide excellent sound attenuation over a wide range of frequencies. The multilayered sheet materials can also be easily shaped into desired contours by application of heat, and optionally pressure, in a contoured tool cavity to provide acoustic panels that conform to various applications. [0008] The acoustic multilayered sheet materials of this invention include an acoustic barrier layer having a relatively high density, a thermoformable sound absorbing layer having a relatively low density, an airflow control layer that is essentially air impermeable, and an acoustic performance enhancement layer. The thermoformable sound absorbing layer is disposed between the airflow control layer and the acoustic performance enhancement layer, and the airflow control layer is disposed between the sound absorbing layer and the acoustic barrier layer. The sheet materials of this invention may include additional layers on either side of and/or between any of the disclosed barrier, sound absorbing, airflow control, and/or acoustic performance enhancement layers. [0009] The acoustic multilayered sheet materials of this invention are useful for preparing contoured sound attenuating panels that conform with and are attached to the metal wall separating the engine component from the passenger compartment of a typical automobile. In a particular aspect of the invention the acoustic multilayered sheet material is installed with the barrier layer directly adjacent to the metal wall. [0010] These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, the claims and the appended drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0011] FIG. 1 is a schematic cross section of an embodiment of the thermoformable acoustic sheet material of the invention. [0012] FIG. 2 is a schematic cross section of an alternative embodiment of the invention. [0013] FIG. 3 is a schematic cross section of a motor vehicle employing the thermoformable acoustic sheet material of FIG. 2. [0014] FIG. 4 is a cross-sectional diagrammatic view of a vertically-lapped nonwoven fibrous mat that may be utilized in the thermoformable acoustic sheet materials of this invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0015] A thermoformable acoustic sheet material 10 comprises at least four layers, including an acoustic barrier or mass layer 12 or 22, a sound absorbing layer 14 or 24, at least one substantially impermeable layer 40, 45, or 28, and a performance enhancement layer 16 or 26, as shown in FIGS. 1 and 2. Sound absorbing layer 14 or 24 is located between barrier layer 12 or 22 and acoustic performance enhancement layer 16 or 26. Substantially, impermeable layer 40, 45 and/or 28 is located between sound absorbing layer 14 or 24 and barrier layer 12 or 22. [0016] Barrier layer 12 or 22 is a relatively high density, thin, flexible layer, selected from resonated cotton shoddy, mineral filled foamed plastic, and, most desirably, a dense fibrous layer. [0017] Preferably, barrier layer 12 or 22 comprises a relatively high density layer of nonwoven fiber that has been compressed to form a sheet or layer having an area weight of from about 40 grams per square foot to about 200 grams per square foot and a thickness of from about 1 millimeter to about 15 millimeters, and more typically a thickness of from about 6 millimeters to about 8 millimeters. Barrier layer 12 or 22 may be vertically-lapped, air-laid, cross-laid, needle-punched or the like. [0018] Alternatively, barrier layer 12 or 22 may comprise a mineral filled foamed plastic material. The mineral filler typically has a specific gravity of from about 4 to about 20. Suitable mineral fillers include barium sulfate and tungsten. Suitable thermoplastic materials that may be employed for fabricating a mineral filled foamed plastic barrier layer 12 or 22 include polyolefins such as polyethylene and polypropylene, rubber modified polyolefins, ethylene-vinyl acetate copolymers, and polyvinylchloride. The mineral filler may comprise up to about 70% of the weight of barrier layer 12 or 22, such that the resulting filled thermoplastic barrier layer 12 or 22 has a relatively high density, typically greater than 1 g/cc. Typically, a mineral filled foamed plastic barrier layer 12 or 22 has a thickness of from about 1 millimeter to about 15 millimeters, and more typically from about 6 millimeters to about 8 millimeters. [0019] As a further alternative, barrier layer 12 or 22 can be fabricated of resonated cotton shoddy. Various resins may be employed in suitable amounts, including thermoplastic resins and/or thermosetting resins, to impart a suitable density and cohesiveness to the barrier layer. Continue reading... Full patent description for Acoustic absorber/barrier composite Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Acoustic absorber/barrier composite patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Acoustic absorber/barrier composite or other areas of interest. ### Previous Patent Application: Torque distributing drive mechanism with limited slip Next Patent Application: Acoustical insulation for motor vehicles Industry Class: Acoustics ### FreshPatents.com Support Thank you for viewing the Acoustic absorber/barrier composite patent info. 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