Sound absorption analysis of carbon steel varied in density and microstructures

In many factories, noise is an important issue considering workers' health and safety; and metal blocks of the machinery is the main source of noise generated while running. Hence, the acoustical characteristics of the metal parts of machineries need to be considered in design. This study aims to determine the effect of metal density to sound absorption (α) in order to reduce noise impact, including its correlation to the metal microstructures. The αvalues of specimen were measured on 5mm thick carbon steel -varies in carbon densities and well-known in metal industries as ST 30, ST 42, and ST 60 standards. Through 5000x magnification of Scanning Electron Microscopic (SEM), the microstructures of carbon steel are identified. The results showed that in the high-frequency range (1200-1400 Hz) the highest α values occurred on ST 60 steel, while in the low-frequency range (200-400 Hz), the α values were relatively similar for all specimen with a small discrepancy on ST 42. Homogenous metal grains with less gaps are clearly shown on ST 30 microstructures, while for ST 60 the grains seem varied in size and types, dominate with carbon particles, making the steel more rigid and better for sound absorptive function.