A Silencer of Exceptional Efficiency T HE requirements of a silencer
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are that it should carry outits work effectively to the necessary 'degree whilst causing the minimum amount of obstruction and, consequently, back
pressure. It must also perform its work for long' periods without the need for attention.
In this connection, the Servais straight-through silencer, made by Servais Services, Ltd., 8, Old Pye Street, London, S.W.1, is of considerable interest.
It is suitable for all types of engine and vehicle, and as its principle is the absorption of sound frequencies over any desired range, it is applicable to aeroplanes, machine guns, road-breaking drills, and, in fact, to any noise caused by the rapid expansion of gases.
It can deal, for instance, with the
gases obtained by firing a pistol through it. This noise which, in the open, is startling, is so reduced by the silencer that persons only a few feet away can hardly realize that a shot has been fired.
The Servais silencer is already in use
on public vehicles, such as the road sweepers operated during the night by Westminster City Council.
As will be seen from the drawing which we reproduce, the silencer consists of a plain cylinder into which are built mesh-held fillings of a porous nature, comprising constantly varying
cells. It is claimed that these cells vibrate within the casing, and by synchronizing with the sound vibrations of the exhaust gases, finally absorb them..