Low-Frequency Noise Reduction by Earmuffs with Flax Fibre-Reinforced Polypropylene Ear Cups

Figure 1

Manufacturing process of the composite ear cups: (a) a stack of flax fabrics and polypropylene films placed on top of one side of the two-piece aluminium mould; (b) hot press compression moulding; (c) unprocessed composite ear cup; (d) processed composite ear cup (bottom image) and assembled earmuff for experiment (top image).