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This paper investigates the noise sources in a pneumatic nail gun. The study combines two complementary experimental approaches. The first uses simultaneous data observation, with sound, acceleration and air pressure signals simultaneously recorded in conjunction with a nail gun motion high speed video. This strategy allows the identification of the physical processes involved in the operation of the machine at different time instants, as well as the associated noise generation mechanisms. However, since multiple noise sources radiate at the same time, this observation technique is not sufficient for noise source identification and ranking. Thus, a second approach introduces a selective wrapping procedure, and the strategy assures a reliable classification of the noise sources. The investigation considers the following noise origins: the air exhaust, the machine body and the workpiece/worktable. In the standardized setup, the workpiece is placed in a sandbox to minimize its noise contribution. Since the final efficiency of this setup has never been established, the study evaluates the sandbox efficiency and compares it with a more realistic test arrangement, where the workpiece is placed on a worktable. The analysis shows that the sandbox setup does not sufficiently attenuate the workpiece noise. With the worktable setup, the workpiece/worktable noise source appears as the main contributor to the total emitted noise, while the air exhaust and the machine body noise are ranked as the second and third sources, respectively. With the sandbox setup, the workpiece noise is reduced, but remains the dominant source with the air exhaust, in equal measure. |
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