I.c. engine exhaust noise suppressor

The noise suppressor comprises a muffler 10 having an inlet pipe 20 and at least one outlet pipe 30 and being partitioned into five chambers 1-5 by four baffles 11, 12, 13, 14. The inlet pipe 20 communicates with the fourth chamber 4 and has a bleed via aperture(s) 24 into the third chamber 3. The outlet pipe(s) 30 communicate(s) with the third chamber 3. The first and fourth chambers 1, 4 communicate via one or two inner pipe(s) 21. The first and third chambers 1, 3 communicate via further inner pipe(s) 22 which may be perforated. The fourth and fifth chambers 4, 5 communicate via a still further inner pipe 23. The chambers may be of different lengths. The outlet pipe(s) 30 may be perforated and partly insulated with a sound absorbent material.