Possibilities of Active Noise Supression for Diesel Engines 785131

90% of noise from Diesel-powered vehicles originates from the engine, exhaust, and cooling system. The paper investigates means of reducing this noise.
Straightforward approaches to noise reduction of exhaust and cooling systems are reviewed. However, improvements of the greatest noise source, the engine, is more problematic. Modification of engine processes themselves is not promising. Engine coverings encompass serious drawbacks involving weight, cost, accessibility, and fire hazard. Improvement guidelines suggest two areas where efforts should be concentrated: the points of noise transfer from engine to the vehicle body, and the noise-emitting body surfaces themselves.
Specific improvements to meet both of these requirements were developed through laboratory tests; they included stiffening of the clutch housing, inclusion of an oil pan brace, and redesign of the intake pipe. These specific improvements offered 3.5 to 4dB(A) noise reductions; further inclusion of exhaust and cooling improvements provided 4 to 6dB(A) total improvements. However, progressive cost increases of noise reductions require better measurement techniques of noise perception in order to target future design work.


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