Sound absorption structure

A sound absorption structure comprising:

• a base duct portion;
• an extended duct portion having a diameter greater than that of said base duct portion, said extended duct portion being connected to said base duct portion;
• a sound absorption material being located at an interior side of said extended duct portion, said sound absorption material including at least one of polyester fiber having an average diameter ranging from 10 to 40 .mu.m and polypropylene fiber having an average diameter ranging from 0.1 to 10 .mu.m;
• and
• a Helmholtz resonator having a resonant frequency corresponding to a resonant frequency range generated by said extended duct portion, said Helmholtz resonator being integrally connected with said extended duct portion.

A sound absorption structure comprising:

• a base duct portion;
• an extended duct portion having a diameter greater than that of said base duct portion, said extended duct portion being connected to said base duct portion;
• a sound absorption material being located at an interior side of said extended duct portion;
• a nonwoven fabric for covering at least a portion of said sound absorption material, said nonwoven fabric comprised of synthetic fiber, said nonwoven fabric having a density ranging from 20 to 200 g/m.sup.2, and said synthetic fiber having a fiber length longer than 10 cm and an average diameter ranging from 1 to 30 .mu.m;
• and
• a Helmholtz resonator having a resonant frequency corresponding to a resonant frequency range generated by said extended duct portion, said Helmholtz resonator being integrally connected with said extended duct portion.

A sound absorption structure for an intake system of an automotive vehicle, said sound absorption structure comprising:

• an inlet base duct portion for connection to a supply of fresh air;
• an outlet base duct portion for connection to the intake system;
• an extended duct portion connected between said inlet and outlet base duct portions and having an inner diameter greater than that of said base duct portions;
• an inner pipe portion coaxially disposed with respect to said extended duct portion and integrally connecting said inlet and outlet base duct portions, said inner pipe portion having a plurality of openings;
• a sound absorption material disposed between said extended duct portion and said inner pipe portion;
• and
• a Helmholtz resonator having a resonant frequency corresponding to a resonant frequency range generated by said extended duct portion, said Helmholtz resonator including a volumetric portion surrounding said extended duct portion and a neck portion connecting said base duct portion to said volumetric portion.