Sound-absorbing duct structure

A sound-absorbing duct structure comprising:

• a sound-absorbing section arranged in communication with a gas passage, including:
• a piezoelectric material exhibiting a piezoelectric effect,
• an electrically conductive material in contact with said piezoelectric material, and
• at least one cavity type resonator connected to said duct and in communication with the gas passage, said cavity type resonator being arranged to have a resonant frequency which is set to attenuate noise in said duct.

A sound-absorbing duct structure comprising:

• a duct defining thereinside a gas passage, a first part of said duct being formed with a plurality of small holes;
• a first expanded duct section formed around the first part of said duct, said expanded duct section defining therein an inside space which is in communication with the gas passage through the small holes, the inside space having a cross-sectional area larger than that of the gas passage;
• and
• a first sound-absorbing section disposed in at least a part of the inside space of said first sound absorbing section including an piezoelectric material exhibiting a piezoelectric effect, and an electrically conductive material in contact with said piezoelectric material;
• and
• wherein said piezoelectric material includes a plurality of piezoelectric layers, and said electrically conductive material includes a plurality of electrically-conductive layers, and
• wherein each piezoelectric layer is interposed between the adjacent two electrically conductive layers so as to form a laminated structure of the piezoelectric layers and the electrically conductive layers.

A sound-absorbing duct structure comprising:

• a duct defining thereinside a gas passage, a first part of said duct being formed with a plurality of small holes;
• a first expanded duct section formed around the first part of said duct, said expanded duct section defining therein an inside space which is in communication with the gas passage through the small holes, the inside space having a cross-sectional area larger than that of the gas passage;
• and
• a first sound-absorbing section disposed in at least a part of the inside space of said first sound absorbing section including an piezoelectric material exhibiting a piezoelectric effect, and an electrically conductive material in contact with said piezoelectric material;
• and
• wherein said electrically conductive material has a volume resistivity ranging from 10 to 100000 Ω·cm.

A sound-absorbing duct structure comprising:

• a duct defining thereinside a gas passage, a first part of said duct being formed with a plurality of small holes;
• a first expanded duct section formed around the first part of said duct, said expanded duct section defining therein an inside space which is in communication with the gas passage through the small holes, the inside space having a cross-sectional area larger than that of the gas passage;
• and
• a first sound-absorbing section disposed in at least a part of the inside space of said first sound absorbing section including an piezoelectric material exhibiting a piezoelectric effect, and an electrically conductive material in contact with said piezoelectric material;
• and
• wherein said piezoelectric material is a film formed of polyvinylidene fluoride and subjected to a poling treatment.

A sound-absorbing duct structure for an intake system of an automotive internal combustion engine, comprising:

• a duct defining thereinside a gas passage, a part of said duct being formed with a plurality of small holes, said duct being connected to an air intake duct of an air cleaner so that the gas passage forms part of an air intake passage through which intake air is supplied to the engine;
• a sound-absorbing section in communication with the gas passage, through the small holes, said sound-absorbing section including an piezoelectric material exhibiting a piezoelectric effect, said piezoelectric material being adapted to generate electric charge upon application of sound pressure in said first expanded duct section, and an electrically conductive material in contact with said piezoelectric material, said electrically conductive material being adapted to be supplied with the electric charge from said piezoelectric material so as to consume the electrical charge;
• and
• means for causing a gas to flow through the gas passage so as to allow a sound pressure due to flow of the gas is absorbed in said sound-absorbing section.

A sound-absorbing duct structure for an intake system of an automotive internal combustion engine, comprising:

• a duct defining thereinside a gas passage, a part of said duct being formed with a plurality of small holes, said duct being connected to an air intake duct of an air cleaner so that the gas passage forms part of an air intake passage through which intake air is supplied to the engine;
• an expanded duct section formed around the part of said duct, said expanded duct section defining therein an inside space which is in communication with the gas passage through the small holes, the inside space having a cross-sectional area larger than that of the gas passage;
• and
• a sound-absorbing section disposed in at least a part of the inside space of said expanded duct section, said sound absorbing section including an piezoelectric material exhibiting a piezoelectric effect, and an electrically conductive material in contact with said piezoelectric material.