Muffler unit for fume extractor hood

1. A fume extractor hood comprising:

a motor unit comprising a conduit that houses a motor for actuating a fan for air suction;

a plate comprising a filter adapted to be arranged above a space where fumes are to be sucked;

a muffler unit removably mountable between said motor unit and said plate,

wherein said muffler unit comprises

an active noise suppression system comprising at least a loudspeaker,

at least two microphones connected to a control unit,

a passive noise suppression system comprising a sound-absorbent material arranged between said microphones, and

a conduit with an upper fixing element and a lower fixing element removably fixable to said motor unit and to said plate, respectively,

wherein said conduit of said muffler unit has a pentagonal transversal section.

2. The fume extractor hood according to claim 1 , wherein the pentagonal transversal section of said muffler unit includes sides having inner corners and outer corners,

wherein the adjacent sides are connected each other at the inner corners and free of direct attachment to each other at the outer corners.

3. The fume extractor hood according to claim 2 , wherein the sides of the pentagonal transversal section of said muffler unit are a regular pentagon with five equal sides.

4. The fume extractor hood according to claim 1 , wherein the loudspeaker is arranged in a lower part of said conduit of said muffler unit, in a coaxial position with said conduit, and includes a sound-emitting surface facing upward.

5. The fume extractor hood according to claim 1 , wherein the loudspeaker is arranged in a lower part of said conduit of said muffler unit, in a coaxial position with said conduit, and includes a sound-emitting surface facing downward.

6. The fume extractor hood according to claim 5 , wherein said muffler unit further comprises

a cover arranged in the lower part of said conduit of said muffler unit and supporting the loudspeaker, and

radial brackets connected to said conduit of said muffler unit and supporting the loudspeaker to form an annular space between the cover and said conduit of said muffler unit for the air being sucked to pass through.

7. The fume extractor hood according to claim 6 , wherein the cover has a truncated-conical shape and is situated under the lower part of said conduit of said muffler unit.

8. The fume extractor hood according to claim 7 , wherein the cover has an ogival shape and is situated inside said conduit of said muffler unit.

9. The fume extractor hood according to claim 6 , wherein said muffler unit further comprises a sound-absorbent element arranged above said cover in a coaxial position with respect to said conduit of said muffler unit.

10. The fume extractor hood according to claim 1 , wherein said sound-absorbent material is an open-cell material.

11. The fume extractor hood according to claim 10 , wherein the sound-absorbent material is melamine foam.

12. The fume extractor hood according to claim 1 , wherein

said conduit of said muffler unit comprises a central portion and a lower portion, and

the central portion is connected by a tapered connection wall to the lower portion in which the loudspeaker is arranged coaxially.

13. The fume extractor hood according to claim 12 , wherein the at least two microphones are

at least one reference microphone arranged in said central portion of said conduit, and

at least one error microphone is closer to the loudspeaker than the reference microphone.

14. The fume extractor hood according to claim 12 , wherein the error microphone is arranged under said loudspeaker.

15. The fume extractor hood according to claim 1 , further comprising another muffler unit mounted between said motor unit and the fume exhaust conduit of the hood.

16. A muffler unit for a fume extractor hood including a motor unit for actuating a fan for air suction and a plate including a filter arranged above a space where fumes are to be sucked, the muffler unit being removably mountable between the motor unit and the plate and comprising:

an active noise suppression system comprising at least a loudspeaker;

a control unit;

at least two microphones connected to the control unit,

a passive noise suppression system comprising a sound-absorbent material arranged between said microphones; and

a conduit with upper fixing element and lower fixing element removably fixable to the motor unit and to the plate, respectively,

wherein

a transversal section of said conduit of the muffler unit has an odd number of sides, and

the sides of the transversal section of the conduit are connected to each other at inner corners of the adjacent sides and free of direct attachment to each other at outer corners of the adjacent sides.