Noise and vibrations are fatiguing to the driver and passengers on a long journey, even though the sound level as such may not be objectionable.
|The moulded glassfibre roof lining is covered with velour and provides insulation against noise, heat and cold, as well as an impact-absorbing surface covering the roof and reinforcing members.|
Comparative tests carried out by the motoring press demonstrate that the sound level in a Saab 900 is lower than in most other cars in the same price and performance class. This is the result of careful insulation and a variety of measures designed to suppress the sound at source.
The engine is mounted on pre loaded rubber elements enclosed in metal cases. Cars with turbo-charged engines are also equipped with hydraulic engine mountings. The steering gear is rubber-insulated. The choice of ventilation fan has been guided by sound level considerations rather than capacity level alone. The curved windscreen and the low, smooth front provide exceptionally good aerodynamics and thus a low level of wind noise. The glassfibre roof lining, the parcel shelf and the polyurethane foam side trim (on the two door and three door models) are some of the sound-attenuating elements. The bulkhead between the engine bay and the interior is insulated on the inside, and the insulation is covered with a thin, pressed plate. The bon net insulation consists of sound-deadening polyester foam. The surface is fluted for maximum absorption of road noise and engine sound. The carpet is backed by a thick layer of fluted polyester foam, bonded to a bitumen panel.
|The more powerful models are equipped with hydraulic engine mountings that attenuate vibrations very effectively||The hydraulic engine mounting has two chambers containing a special damping fluid. The chambers are separated by a diaphragm which takes up normal engine vibrations. If larger engine movements should occur, the fluid will be forced through a port from the upper to the lower chamber, equalising the pressures. The damping action of the mounting is therefore progressive, with the resistance to movement increasing with load.|
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