Acoustics – Sound-modifying means – Sound absorbing panels
Patent
1999-03-24
2000-11-14
Dang, Khanh
Acoustics
Sound-modifying means
Sound absorbing panels
286294, E04B 182
Patent
active
061456179
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a multifunctional kit for the noise reduction and heat insulation in vehicles, according to the preamble of claim 1.
Large areal vehicle parts, such as floor sheeting, roof sheeting, boot lids, end faces or doors and side coverings tend to deform, vibrate and oscillate on travelling on account of their low inherent stability. This behaviour is conventionally counteracted by mounting damping material, in particular of heavy layers of bitumen. In order to reduce the transmission of travelling noises in the inside of the vehicle, in the automobile industry, since a long time, additionally, multi-layered sound insulation assemblies have been applied. In particular by way of these sound insulation assemblies, noises from the vehicle motor, from the gearbox and auxiliary units, from exhaust systems but also wind and tire noises are effectively insulated. These sound insulating assemblies as a rule are conceived as spring-mass-systems and all comprise an airtight heavy layer coupled to an elastic spring layer in order to damp the vibrations of the large areal car body parts and to insulate the airborne noise.
Such a sound insulating package is for example described in EP-0'334'178 and comprises essentially a soft-elastic foam material layer which faces the car body part capable of oscillation and which acts as the spring of the spring-mass system, an almost compact, air-impermeable and consolidated layer of the same material, which acts as the mass of the spring-mass-system, wherein this for consolidation is incorporated into a frame of fleece or cut foam, as well as a decor covering or carpet layer arranged thereabove. By way of this construction the weight of the heavy layer may be reduced up to 40% and thus also the weight of the whole sound insulation system may be reduced with respect to the known spring-mass-systems, but however at the cost of the acoustic effectiveness.
In EP-0'255'332 a sound insulating package is disclosed which with the help of a semi-flexible carrier layer, in the manner of a snap closure, is tensioned against the vehicle roof. With this carrier layer a classic spring-mass-system of a resilient, sound-absorbing foam layer and of a visco-elastic, closed-pored heavy layer (filled with bitumen) is pressed against the vehicle roof. By way of the non-positive connection of the heavy layer to the vehicle roof the vibrations of this are damped better and the heavy layer no longer needs to cover the whole surface.
Generally spring-mass arrangements however lead to the onset of resonance in the sound insulation, which usually lie in the frequency range of the lower motor arrangements and here are particularly undesirable. This phenomenon as a rule forbids an extremely light construction.
It is the general desire of the automobile industry to reduce the weight of vehicles. This has the result that increasingly also thinner and lighter car body parts are applied, which leads to considerable acoustic disadvantages. The demands on the sound insulation assemblies are significantly increased by the use of lightweight car body parts.
It is therefore the object of the invention to provide an ultra-light kit which also with lightweight car body parts, for example of aluminium or plastic, has no loss of acoustic effectiveness.
In particular a sound-insulating kit is to be provided which is more than 50% lighter than conventional sound-insulating assemblies and furthermore has good heat-insulating properties.
According to the invention this object is generally achieved by a kit with the features of claim 1 and is particularly achieved in that the air-impermeable heavy layer with conventional spring-mass systems is replaced by a relatively thin, micro-porous and stiff fibre layer, or fibre/foam composite layer. This micro-porous fibre layer is open-pored and has a relatively high airflow resistance. Essential for the solution of the object set is the formation of an air layer in the sound-absorbing kit, the air layer preferably lying between the areal car body part and the
REFERENCES:
patent: 5298694 (1994-03-01), Thompson et al.
patent: 5493081 (1996-02-01), Manogold
Dang Khanh
Rieter Automotive AG
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