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Technical Paper

Study on Exterior Idling Sound Quality Evaluation Method for Diesel Engine Trucks

1999-05-17
1999-01-1739
In diesel engine trucks, the sound quality improvement as well as the noise level reduction is demanded because of their annoying exterior noise. The semantic differential method was applied to evaluate the sound quality of trucks. In order to improve the analytical accuracy, subjects who can evaluate the characteristics of sound quality were statistically selected among all the subjects. Comfortability and powerfulness were extracted as the principal components by using the data of the selected subjects. It has been clarified that the comfortability strongly relates to high frequency element ratio, high frequency level, etc. The powerfulness strongly relates to the Zwicker loudness.
Technical Paper

Noise Generating Mechanism at Idling for a Four-cylinder In-line Diesel Engine

2003-05-05
2003-01-1720
The separation of combustion noise and mechanical noise from the total noise of a four-cylinder in-line diesel engine at idling was carried out with high accuracy by changing the fuel injection timing. The mechanical noise, which accounts for the major share at 93%, was then separated into noises from the typical mechanical causes, and the valve train was found to be the major noise source. From analysis of the noise generating mechanism for the valve train, it was clarified that the noise was caused mainly by the gear rattling owing to the variation in the camshaft drive torque.
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