Mathematical modelling of sound transmission loss (STL) in metallic and graphite based coatings

This study aimed to investigate the relationship between the sound transmission loss (STL) properties and surface morphologies of metallic-based and graphite-based coatings. Aluminium (22 mu m average particle size (APS) and 12 mu m APS), copper (12 mu m APS), silver (14 mu m APS) as conductive metal pigments and graphite (18 mu m APS) as a semi-conductive pigment were used to create coatings and STL properties were measured with an in-house designed sound wave modulation device. Laser beams with different carrier wavelengths were used in the experiment, for which the wavelength with the highest R-2 and number of significant variables was used to create a mathematical model to help in measuring the sound transmission loss properties. Surface tension energy, conductivity, permeability, reflectivity, concentration and the type of pigment were found to be significant in determining the STL properties.