SOUNDLESS MOTORING.

Auckland Star, Volume LXVIII, Issue 158, 6 July 1937, Page 16

SOUNDLESS MOTORING.

NEW INSULATION PRINCIPLE. What is this new sound insulation that has proved such a popular feature with some of the latest saloons ? Briefly, it comprises the attachment to the panel of a soft non-vibrating material which absorbs reflected sounds and damps any panel vibrations which might generate noise. The material used is in sheet form, and consists of a fibrous content loosely felted between waterproof walls and is cemented to the steel floor, roof and scuttle panels, as well as to the side panels of the new saloons. Its surface is embossed, the raised portions on one side coinciding in position with the depressions on the other, and the sheet adheres to the body panels only at the crests of the embossing, to leave a number of enclosed, or "dead" air cells between the metal and the sheet. These break up the sound vibrations into small groups, each being confined to one air cell. The sound waves that traverse this air space and reach the fibrous constituent of the insulations are very largely absorbed by the hollow fibres, but" as all the sound cannot be absorbed in this way, the insulating sheet has a skin of asphalt on its inner surface, i.e., that towards the inside of the body, which reflects back unabsorbed sound waves into the material to increase the efficiency of absorption and give a high percentage of sound elimination. Additionally this insulation has a damping action ' on the natural resonance of the steel panels by virtue of its intimate contact with them; it has the further advantao-o of keeping the interior of the car warmer in winter and cooler in summer, for it is also an excellent heat insulator. .Reports received from owners of these new, sound-insulated models indicate , not only the success of this new develop- \ ment, but also appreciation of the foresight which saw the need of soundinsulation, and of the initiative that has made it an accomplished fact.