Resonator

1. A resonator comprising:

a neck portion; and

a resonator main body comprising:

(a) a main volume chamber communicated with an air intake duct of an internal combustion engine for a vehicle via the neck portion; and

(b) at least one sub-volume chamber directly connected to the main volume chamber,

wherein the resonator main body is configured to have both (i) a Helmholtz-resonator functional part whose resonance frequency is determined based on a total volumetric capacity of the resonator main body, substantially corresponding to a summed value of a volume of the main volume chamber and a volume of the sub-volume chamber, and (ii) a side-branch-resonator functional part whose resonance frequency is determined based on a summed length of a longitudinal length of the sub-volume chamber and a length of a hypothetical extension of the sub-volume chamber, which extension is obtained by hypothetically extending the sub-volume chamber into the main volume chamber in a longitudinal direction of the sub-volume chamber.

2. The resonator as claimed in claim 1 , wherein:

the resonator main body is formed into a substantially L-shape by directly connecting only one elongated sub-volume chamber to the main volume chamber; and

the resonator main body is configured, so that the longitudinal direction of the sub-volume chamber is identical to a lateral direction of the vehicle, and that the resonator main body is arranged in close proximity to an air intake of the air intake duct, which air intake opens at a front end of the vehicle in a manner so as to be directed forwardly of the vehicle, and that the sub-volume chamber is arranged along a front end face of the vehicle.

3. The resonator as claimed in claim 2 , further comprising:

a dummy air intake having a substantially same outline as the air intake of the air intake duct as viewed from the front end face of the vehicle, and attached to the sub-volume chamber, so that the air intake and the dummy air intake are symmetrical to each other with respect to a reference line that indicates a central position in the lateral direction of the vehicle.

4. The resonator as claimed in claim 1 , further comprising:

an additional side-branch resonator connected to the air intake duct, and formed integral with the resonator main body.

5. The resonator as claimed in claim 4 , wherein:

the additional side-branch resonator is configured to extend along a lower face of the sub-volume chamber of the resonator main body.

6. A resonator comprising:

a neck portion; and

a resonator main body comprising:

(a) a main volume chamber communicated with an air intake duct of an internal combustion engine for a vehicle via the neck portion; and

(b) a plurality of sub-volume chambers directly connected to the main volume chamber,

wherein the number of the sub-volume chambers is an even number to provide a plurality of pairs of sub-volume chambers, central axes of each of the pairs of sub-volume chambers are identical to each other, and longitudinal lengths of the pairs of sub-volume chambers differ from each other, and

wherein the resonator main body is configured to have (i) a Helmholtz-resonator functional part whose resonance frequency is determined based on a total volumetric capacity of the resonator main body, substantially corresponding to a summed value of a volume of the main volume chamber and volumes of the sub-volume chambers, and (ii) a plurality of side-branch-resonator functional parts whose resonance frequencies are determined based on the longitudinal lengths of the respective pairs of sub-volume chambers.

7. A resonator comprising:

a neck portion; and

a resonator main body comprising:

(a) a main volume chamber communicated with an air intake duct of an internal combustion engine for a vehicle via the neck portion; and

(b) a plurality of sub-volume chambers directly connected to the main volume chamber,

wherein central axes of the sub-volume chambers are offset from each other and longitudinal lengths of the sub-volume chambers differ from each other, and

wherein the resonator main body is configured to have (i) a Helmholtz-resonator functional part whose resonance frequency is determined based on a total volumetric capacity of the resonator main body, substantially corresponding to a summed value of a volume of the main volume chamber and volumes of the sub-volume chambers, and (ii) a plurality of side-branch-resonator functional parts constructed by the respective sub-volume chambers and hypothetical extensions obtained by hypothetically extending each of the sub-volume chambers into the main volume chamber, a resonance frequency of each of the side-branch-resonator functional parts being determined based on a summed longitudinal length of the associated sub-volume chamber and the associated hypothetical extension.

8. A resonator comprising:

a neck portion; and

a resonator main body comprising:

(a) a main volume chamber communicated with an air intake duct of an internal combustion engine for a vehicle via the neck portion; and

(b) a plurality of sub-volume chambers directly connected to the main volume chamber, the plurality of sub-volume chambers comprising:

(1) at least one pair of sub-volume chambers whose central axes are identical to each other; and

(2) at least one offset sub-volume chamber whose central axis is offset from a central axis of the other sub-volume chamber,

wherein the resonator main body is configured to have (i) a Helmholtz-resonator functional part whose resonance frequency is determined based on a total volumetric capacity of the resonator main body, substantially corresponding to a summed value of a volume of the main volume chamber and volumes of the sub-volume chambers, (ii) a first side-branch-resonator functional part, which is constructed by the pair of sub-volume chambers whose central axes are identical to each other and whose resonance frequency is determined based on a longitudinal length of the pair of sub-volume chambers, and (iii) a second side-branch-resonator functional part, which is constructed by the offset sub-volume chamber and a hypothetical extension obtained by hypothetically extending the offset sub-volume chamber into the main volume chamber and whose resonance frequency is determined based on a summed longitudinal length of the offset sub-volume chamber and the hypothetical extension.