Sound absorber having helical fixtures

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 two helical fixture mounted at a longitudinal distance in at least one longitudinal section of the at least one gas channel,
• wherein each of the at least two helical fixture separate two helical gas passages through the at least one longitudinal section of the gas channel;
• wherein the at least two helical fixture define between them at least one longitudinal Helmholtz resonator cavity within the gas channel which is excited by sound waves propagating in the gas passing through the at least one gas channel;
• and
• wherein the at least two helical fixtures comprise longitudinal end regions at their far ends in which outer diameters of the at least two helical fixture taper and get away from a wall of the tube circumferentially enclosing the at least one gas channel such that the outer diameters continuously decrease from an inner diameter of the tube to zero resulting in a low reflection soft impedance transition.

A system comprising:

• at least one of an engine and of a pump;
• and
• a tube including a sound absorber, the sound absorber comprising:
• at least one elongated gas channel, through which a 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.