Development of acoustic material with inline cavity structure for design of operators' cabins in mineral processing plants

Operators of mineral processing plants are exposed to noise levels that may reach up to 100 dB(A). The aim of this study was to find appropriate acoustic materials for the construction of cabins that can protect the operators by reducing noise levels by at least 15 dB(A) in the specific frequency range of 0.5-5 kHz, as the human ear is more sensitive to these frequencies. 3D printed material made from standard resin with an internal inline cavity structure was selected for the design. The position of the cavity in the structure and perforation ratio were varied to investigate their acoustic properties. Acoustic properties such as the Sound Absorption Coefficient (SAC) and Sound Transmission Loss (STL) were measured using the Impedance Tube Apparatus. A maximum SAC of 99.6% was observed at 5.225 and 5.625 kHz among the test samples. The peak SAC shifted towards lower frequencies when the cavity was away from the inlet port. By decreasing the perforation ratio from 13.25% to 1.28%, the STL increased up to 48 dB. We conclude that our designs have great potential for the construction of operator's cabins which provide attenuation of at least 20 dB in the desired frequency range.