Study of noise transmission from an electric impact wrench.
Markesino-J; Pruse-R; Rao-MD
NOISE-CON 2004: Proceedings of the National Conference on Noise Control Engineering, Baltimore, Maryland, July 12-14, 2004. Burroughs C, Maling Jr G, eds., Ames, IA: Institute of Noise Control Engineering of the USA, 2004 Jul; :154-160
Under free-run, it was concluded that the noise from the impact wrench was airborne and resulted from the airflow through the intake and exhaust vents. To control this noise without affecting the performance of the impact wrench, a muffler/redirector was implemented to direct the exhaust flow away from the operator's ears and out toward the handle of the tool. Additional recommendations include modifying the geometry of the fan blades. This may work to reduce the airborne noise generated by their rotational motion. Currently, the blades are straight and generate a large amount of air disturbance, which results in noise generation. By implementing a small radius on the ends of the fan blades air turbulence would be reduced thus reducing the radiated noise. Identifying potential solutions for reducing the noise level of the impact wrench under load was a great deal more challenging compared to the unloaded case. Attempts to isolate the impact between the hammer ears and output shaft wings resulted in minimal success. The noise level reduction achieved in the mock-up study was approximately 2 dB at best, and the materials used for isolation did not possess the durability to withstand the impact forces generated within the tool. Further research and testing is recommended to validate the concepts attempted in the study. The final test, which incorporated lining the interior of the nose cone with damping material, placing a gasket between the interface of the nose cone and housing, and the use of dual exit exhaust produced the most significant sound pressure level reduction of 3 dBA. This reduction would be noticeable to the operator.
Power-tools; Noise; Noise-frequencies; Noise-analysis; Noise-propagation; Impact-noise; Sound-propagation; Noise-waves; Noise-control; Work-areas; Work-environment; Workplace-studies; Hearing-threshold; Noise-exposure; Noise-levels; Noise-measurement; Noise-pollution; Noise-shielding; Noise-sources; Noise-transmission; Air-flow; Air-treatment-equipment
Structural Dynamics Research Laboratories, Mechanical, Industrial and Nuclear Engineering Department, University of Cincinnati, Cincinnati, OH 45221-0072, U.S.A.
Burroughs-C; Maling-G Jr.
NOISE-CON 2004: Proceedings of the National Conference on Noise Control Engineering, Baltimore, Maryland, July 12-14, 2004