| CPC F01N 1/08 (2013.01) [G10K 11/162 (2013.01)] | 12 Claims | 

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               1. A method of reducing refracted sound from a power station, the power station comprising a gas turbine and an exhaust duct assembly having an exhaust gas outlet for exhausting exhaust gas into the atmosphere, the method comprising: 
            positioning an acoustic duct portion upstream of the exhaust gas outlet, the acoustic duct portion having a peripheral wall defining a through-passage arranged and constructed to promote propagation of sound there-through to atmosphere, the peripheral wall including an acoustically porous structure, and wherein the acoustic duct portion has a length (L) in a flow direction that is at least 50% of an average hydraulic diameter (DH) of the through-passage; and 
                operating the gas turbine, 
                wherein noise from the exhaust gas propagates through the acoustically porous structure to atmosphere so as to reduce refracted sound at locations downwind from the exhaust gas outlet. 
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