Abstract: A combined device is provided for positioning between the outlet of a gas turbine and a steam generator. The combined device acts as a sound-absorber and as a diffusor and is designated a gas turbine muffler. The gas turbine muffler has an inner zone which widens out in the flow direction S at a relatively large angle. Deflector elements arranged in this inner zone delineate diffusor channels, that are located between adjacent deflector elements. The diffusor channels widen out in each case at a significantly smaller acute angle of less than 7.degree.. In addition to decelerating the stream of gas and hence, in addition, increasing the pressure, the narrow diffusor channels also bring about sound-absorption by reducing the regions of turbulence, making the stream more uniform, and aligning the stream.