The present invention relates generally to acoustical insulation materials and, more particularly, to acoustical insulation materials utilized within vehicles.
It is generally considered desirable to reduce the level of noise within a vehicle passenger compartment. Noises, such as road noise, engine noise, vibrations, etc., may be attenuated through the use of various acoustically absorptive (or reflective) materials. For example, sound attenuating materials are conventionally provided in conjunction with carpeting for floor panels, upholstery for door panels and headliners, etc.
Various sound attenuating materials have been developed for use in reducing noise levels within passenger compartments of vehicles. For example, U.S. Pat. No. 4,851,283 to Holtrop et al., proposes a thermoformable laminate for use in headliners. The headliner comprises a non-woven fabric bonded to a foamed polymer sheet. The fabric is formed from a blend of low melting staple fibers and high melting staple fibers.
U.S. Pat. No. 5,298,694 to Thompson proposes a non-woven acoustical insulation web. The web comprises thermoplastic fibers, and particularly a blend of melt-blown microfibers and crimped bulking fibers.
U.S. Pat. No. 5,677,027 to Masuda et al., proposes a sound insulating structure comprising a covering layer, a panel, and a cushioning layer. The cushioning layer comprises a first fiber such as polyethylene terephthalate (PET) and a second fiber that is of a shell-core construction wherein the majority of the core is PET.
U.S. Pat. No. 5,817,408 to Orimo et al., proposes a sound insulating structure which includes low and high density thermoplastic fibers. PET is preferred as a thermoplastic synthetic fiber.
U.S. Pat. No. 4,529,639 to Peoples, Jr. et al. proposes a molded foam-backed carpet assembly which includes a carpet layer, a moldable thermoplastic polymer layer and one or more foam pads fusibly bonded to the thermoplastic layer and extending over less than the entire surface of the thermoplastic polymer layer to provide desired cushioning and sound and thermal insulation only in preselected areas of the carpet.
In general, the ability of conventional materials to attenuate sound increases as the amount of material increases. Unfortunately, increased materials often increases the weight of sound attenuating material, which may be undesirable. Accordingly, there is a continuing need for acoustical insulation materials that exhibit superior sound attenuating properties, while also being lightweight and low in cost.
In view of the above discussion, sound attenuating composite articles, and methods of making the same, are provided that can utilize a wide variety of fiber and/or foam acoustic layers to achieve various acoustic and functional goals. According to embodiments of the present invention sound attenuating composite articles include first, second, third, and fourth layers of material which are joined together. The first layer of material may be either an acoustic fiber batting and/or an acoustic foam material and may be an elastic or inelastic material. The second layer of material is a thermoplastic material that is fused to a surface of the first layer of material. The third layer of material is a thermoplastic material that is fused to a surface of the second layer of material. The fourth layer of material is a blend of fibers (woven or non-woven), such as scrim material, that is attached to a surface of the third layer of material. Selected portions of the sound attenuating composite article are heated and then compressed so as to have an acoustic impedance that is greater than an acoustic impedance of adjacent portions.
According to embodiments of the present invention, sound attenuating composite articles include first, second, and third layers of material which are joined together. The first layer of material may be either an acoustic fiber batting and/or an acoustic foam material and may be an elastic or inelastic material. The second layer of material is a thermoplastic material that is fused to a surface of the first layer of material. The third layer of material is a thermoplastic material that is fused to a surface of the second layer of material. Selected portions of the sound attenuating composite article are heated and then compressed so as to have an acoustic impedance that is greater than an acoustic impedance of adjacent portions.
Sound attenuating composite articles according to other embodiments of the present invention include first and second layers of material which are joined together. The first layer of material may be either an acoustic fiber batting and/or an acoustic foam material and may be an elastic or inelastic material. The second layer of material is a thermoplastic material that is fused to a surface of the first layer of material. Selected portions of the sound attenuating composite article are heated and then compressed so as to have an acoustic impedance that is greater than an acoustic impedance of adjacent portions.
Sound attenuating composite articles according to other embodiments of the present invention include first, second, and third layers of material which are joined together. The first layer of material may be either an acoustic fiber batting and/or an acoustic foam material and may be an elastic or inelastic material. The second layer of material is a thermoplastic material that is fused to a surface of the first layer of material. The third layer of material is a blend of fibers (woven or non-woven), such as a scrim material, that is attached to a surface of the first layer of material. Selected portions of the sound attenuating composite article are heated and then compressed so as to have an acoustic impedance that is greater than an acoustic impedance of adjacent portions.
Methods of producing sound attenuating composite articles according to embodiments of the present invention include providing an acoustic fiber batting and/or acoustic foam material; extruding a thermoplastic material onto the first layer of material as a second layer of material; compressing the first and second layers of material, such as via nip rolls; extruding a thermoplastic material onto the second layer of material as a third layer of material; attaching a material, such as scrim material, to a surface of the third layer of material as a fourth layer of material; compressing the first, second, third, and fourth layers of material, such as via nip rolls, to a combined, predetermined thickness; heating selected portions of the composite article, and compressing the selected portions so as to have an acoustic impedance that is greater than an acoustic impedance of adjacent portions. Various combinations and numbers of layers may be utilized according to embodiments of the present invention.
Sound attenuating composite articles according to embodiments of the present invention can be xe2x80x9ctunedxe2x80x9d to provide desired sound deadening and absorption properties in selected vehicle locations, such as floor pans, door panels, etc. The term xe2x80x9ctunedxe2x80x9d means that portions of a composite article can be formed to have a specific acoustic impedance designed to attenuate sound in one or more frequencies or frequency bands. Moreover, sound attenuating composite articles according to embodiments of the present invention may have reduced overall weight compared with conventional sound proofing materials, and without sacrificing sound attenuation properties.