Evaluation of Ducting and Absorptive Techniques for the Control of Pneumatic Noise

Abstract

Pneumatic power is used extensively throughout industry and can be a major contributor to elevated noise levels within a shop. Traditionally, pneumatic noise has been controlled using mufflers specifically designed for noise reduction. This study was intended to investigate the use of flexible hose for ducting released air and the resulting noise away from the working area or to a sound-absorbing box. The effects of hose length and thickness were evaluated as well as the effect of altering the exhaust direction at the end of the tube. Measurements were taken near the release point, near the end of the tubes, and near the absorptive boxes. Back pressure was measured for each noise control device evaluated in the study.

Noise reduction increased with increasing tube length, yet absorptive box size had little effect on attenuation results (contrary to theoretical considerations). Back pressure increased with increased tube length; however, overall back pressure increases were low. Changing exhaust direction at the end of the tube had some effects on noise levels; however, using this technique to obtain extra noise reduction is not recommended. Statistically significant (p < 0.005) noise reductions were obtained with all the tube lengths and box sizes tested. The use of flexible tubing directed away from a work area or into a sound-absorbing box was shown to be an effective control of air release noise.