1. A sound-absorbing channel element having large cross-sectional dimensions (1 ; 101 , 102; 201) for a flowing medium, and having an inlet (2) connected to a sound source (15) and an outlet (3), which channel element is defined by outer walls (4) extending in the flow direction, characterized in that the channel element is divided into part-channels (7) running in the direction of flow, each part- channel being provided with sound-absorbing means (8), and at least some of the part-channels (7) being of different lengths and comprising sound-absorbing means tuned for different frequencies.
2. A channel element as claimed in claim 1 , characterized in that it is composed of a plurality of channel element modules, each forming one or more part- channels or part of a part-channel.
3. A channel element as claimed in either of claims 1 or 2, characterized in that the part-channels (7) are constructed from a plurality of pipes (56') running in the direction of flow.
4. A channel element as claimed in either of claims 1 or 2, characterized in that said part channels are constructed from at least one partition wall (5) running in a first direction transverse to the direction of flow.
5. A channel element as claimed in either of claims 1 or 2, characterized in that said part channels are constructed from at least one partition wall (5) running in a first transverse direction and at least one second partition wall (6) running in a second transverse direction to the direction of flow.
6. A channel element as claimed in any one of claims 1-5, characterized in that the part channels (7, 7') are constructed from partition walls (56, 5') that are rigidly joined to the outer walls (4) of the channel element.
7. A channel element as claimed in any one of claims 1-6, characterized in that said inlet (2) is located in a plane forming a first angle to the direction of flow and in that said outlet is located in a plane forming a second angle (3) to the direction of flow, which first and second angles are different. 13
8. A channel element as claimed in claim 7, characterized in that one of said angles is a right angle and the other is 67.5°.
9. A channel element as claimed in any one of claims 1-8, characterized in that at least some of said sound-absorbing means (8) comprise both resistive (12) and reactive (10) sound-absorbing means.
10. A channel element as claimed in claim 9, characterized in that the reactive sound-absorbing means is a resonator (10).
11. A channel element as claimed in claim 10, characterized in that the resonator is a quarter-wave resonator (10).
12. A channel element as claimed in claim 11 , characterized in that the sound-absorbing means (8) comprises a partition wall (11) separating a passage (9) through the part-channel (7) from a side chamber (10) in the part-channel, which side chamber (10) is connected to the passage (9) through the opening member (13) comprising at least one opening, and which partition wall (11) comprises a layer (12) of sound-absorbing material on at least the side of the partition wall (11) facing the passage (9).
13. A channel element as claimed in claim 12, characterized in that the opening member (13) has an area in the same order of magnitude as the through- flow area of the passage (9).
14. A set of channel elements in which each channel element consists of a channel element as claimed in any one of claims 1-13, characterized in that each channel element has an inlet and/or an outlet that is complementary with an outlet and/or inlet, respectively, of another channel element in the set.
15. A set of channel elements for use in a channel element of the type claimed in any one of claims 1-13, characterized in that the set comprises modules of different lengths but having substantially the said cross-sectional dimensions.
16. A gas outlet channel having an inlet (14) connected to a sound source (15) and an outlet (16), which channel is defined by outer walls extending in the 14
flow direction of the gas, characterized in that the channel comprises a plurality of channel elements (1) as claimed in any one of claims 1-13.
17. A gas outlet channel as claimed in claim 16, characterized in that the channel elements (1) constitute a set of the type claimed in claim 14.
18. A gas outlet channel as claimed in either of claims 16 or 17, which channel comprises a bend (18), characterized in that at least one (1b, 1c) of the channel elements is arranged in the bend (18).
19. A method of manufacturing a channel element as claimed in any one of claims 1-13, characterized in that the channel element is composed of a set of channel element modules of the type claimed in claim 15.
20. A method of suppressing the sound in a gas outlet channel having an inlet connected to a sound source and an outlet, which channel is defined by outer walls extending in the direction of flow of the gas, characterized in that the channel is composed of a plurality of channel elements of the type claimed in any one of claims 1-15.
21. The use of channel elements as claimed in any one of claims 1-14 for sound-absorption in a gas outlet channel of the type claimed in any one of claims