Down to 8OdBA with a D600
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• Relatively simple modifications of a Ford D600 platform vehicle, equipped with the maker's 360 cu. in. diesel engine, have been 'made by technicians of the Automotive Engineering Group of the Institute of Sound and Vibration Research, Southampton University, which reduce the overall noise level under test conditions from 884c1BA to 80dBA.
Paul Brockington reports that conversation with the driver is possible in the cab without raising the voice when the vehicle is driven under full load in the gears or in top gear. The noise level in the cab is approximately the same as the level outside the cab.
While precise details of the conversions cannot be revealed, it can be said that they basically comprise the fitting of sound-insulating covers over the valve cover, the sump and the front parts of the engine, including the fan. An additional silencer has also been added.
It is noteworthy that the existing maximum noise level for cars is 84dBA and that the level will be reduced to 80dBA as from April 1, 1973. While the noise regulations announced by Mr John Peyton, Minister for Transport Industries, last week provide for a reduction in level of commercial vehicles equipped with engines of less than 200 bhp from 89dBA to 86dBA in 1973 it is generally anticipated that the level will be further reduced in due course.
Research work at the Institute has shown that fitting a cover over the engine can aid cooling because it enables air flow to be more accurately controlled. Technicians of the Institute favour mounting the radiator in a position other than in front of the engine because the engine inhibits air flow. Reducing fan noise in the case of an engine with the fan mounted on the front of the crankshaft is a particularly difficult problem because it is impossible to reduce the top speed of the fan by employing a larger fan driven at a lower speed.