Empirical study for noise reduction of an impact power wrench and jig saw.
Kulkarni-P; Coombs-D; Giachetto-M; Wade-D; Buchholz-T; Kim-J
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; :140-147
This project involves case studies of two commonly used power tools to study their noise characteristics and develop methods to reduce the noise levels. When comparing the load and no load measurements in case of the impact wrench, it is observed that the impact of the socket hitting the bolt also had a dominant effect. The impact wrench has dominant peaks in the SPL at about 5 kHz and 12 kHz, which are caused either by the hammer anvil impacts or the impacts of socket hitting the bolt. Propagation and reflection of the impact stress wave may have to be studied to better understand the noise generation mechanism. Short Time Fourier Transform of the impact wrench noise as shown in Figure 9 indicates strong presence of impulsive noise. It is believed that more study is necessary to evaluate the health risk of such highly transient sound. Predominant noise is observed at frequencies corresponding to the internal motor, especially the brush contacts, and gear mechanisms in the case of jig saw. Attenuation could be obtained by changing the number of commutator segments or using a brushless motor. The cooling fan blade pass frequency could be changed by reducing the number of blades in order to attenuate the noise level at lower frequencies in the A-weighted plot. In both these cases the actual results of the noise reductions are confirmed by comparing the SPLs measured before and after the noise reduction measures were applied.
Power-tools; Noise; Noise-frequencies; Noise-analysis; Noise-propagation; Impact-noise; Sound-propagation; Noise-waves; Noise-control
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