The aim of this study is to determine the effect of sub-micron fibre web layers on sound absorption properties when they are placed on rigid substrate and flexible substrate. Elastomeric thermoplastic polyurethane (TPU) and composite TPU/PS (polystyrene) sub-micron fibre webs with both rigid glass fibre fabric reinforced epoxy composites (GFEC) and flexible polypropylene (PP) spunbond nonwovens have been examined. Elastomeric TPU sub-micron fibres and TPU/PS fibre web before and after soxhlet extraction were studied. Even though a thin layer of (less than 1 mm) electrospun sub-micron fibres were used with GFEC, sound absorption coefficient (SAC) improved from 0.1 to 0.4. Maximum SAC is drawn back to lower frequency (from 1250 to 500-630 Hz), when sub-micron fibre web is used on nonwoven. In conclusion, the mechanism of elastomeric thin sub-micron fibre webs on sound absorption for rigid GFEC and for flexible nonwoven is totally different than each other.