A study of noise reduction in McCrone Micronizing Mill using sound enclosure treatment

Abstract

A McCrone Micronizing Mill (micro mill) is used by materials researchers to break materials into smaller pieces or powder for microstructure analysis. To achieve this, material is compacted into solid bits inside a canister, and this canister is placed in the micro mill. During the process of micronizing, a noise disturbance is created because of the high-speed vibration of the particles. The noise levels produced by this process is considered to be excessive and causes not only annoyance, but also there is a potential for hearing damage. The goal of this project was to reduce the noise caused by the process to a more acceptable level. The optimal solution to this problem was to eliminate user interaction. However, such a solution was not practical. Therefore, a path treatment was fabricated such that sound pressure level produced by the micronizing mill is reduced to background level using a full sound enclosure. The enclosure was designed such that it does not interfere with the operation of the mill. Effectiveness of this treatment was measured in terms of change in sound pressure levels, loudness, speech interference level, and transmission loss. Results of this study show that using this novel treatment design, a maximum reduction of up to 14 dB in overall sound pressure level can be achieved.