Paint coatings are commonly used to protect industrial components, but their influence on acoustic behaviour is still not fully understood. The aim of this study is to quantify how the type of paint and the number of coating layers affect the sound absorption of metal, expanded polystyrene (EPS), and extruded polystyrene (XPS) samples. Normal-incidence sound absorption coefficients were measured in an impedance tube over the 100–5700 Hz frequency range for uncoated samples and for samples coated with ceramic paint and water-based acrylic lacquer in one- and two-layer configurations. For metal substrates, applying two layers of ceramic paint resulted in the main resonance being observed to move from about 3.8 kHz to around 3.0 kHz and reduced the peak absorption coefficient from ~0.87 to ~0.60, indicating a clear mass-induced tuning of the resonance frequency. In XPS and EPS samples, coatings generally broadened and flattened the absorption curves while slightly reducing the maximum absorption. For XPS, results were averaged over 17 samples to reduce the effect of material heterogeneity, and measurement uncertainty was evaluated according to ISO 10534-2 [1]. Microscopic observations confirmed that the coatings smooth the surface and partially close open pores; combined with the increased surface mass, this modifies the resonance behaviour of the samples. The results demonstrate that paint coatings can influence the resonance frequency and bandwidth of sound absorption in lightweight structures, which may be exploited in future studies on the passive acoustic tuning of materials. The work is limited to normal-incidence tube measurements and does not include direct thickness measurements or detailed resonance modelling, which will be addressed in further research.