Patent ID: 8312962

Claim:
A sound absorber comprising: at least one elongated gas channel, through which a flowing gas passes in operation of the sound absorber; and at least one helical fixture mounted in at least one longitudinal section of the at least one gas channel, wherein the at least one helical fixture separates two helical gas passages through the at least one longitudinal section of the gas channel; wherein the at least one helical fixture comprises at least one longitudinal end region in which an outer diameter of the at least one helical fixture tapers and gets away from a wall circumferentially enclosing the at least one gas channel resulting in a low reflection soft impedance transition; wherein the at least one helical fixture defines at least one longitudinal Helmholtz resonator within the gas channel which is excited by sound waves propagating in the flowing gas passing through the at least one gas channel; and wherein the at least one longitudinal Helmholtz resonator comprises a longitudinal cavity within the at least one gas channel, which is delimited by opposite impedance steps for the sound waves longitudinally propagating in the gas passing through the at least one gas channel.