Abstract: An acoustic attenuator comprises a first attenuation unit, a second attenuation unit, a welded section, and a communication part. A first acoustic damper is provided on an outer surface of a first acoustic liner, which faces toward a side opposite from an object, to form a first damper space that communicates with an internal space of the object. The second attenuation unit is attached to an outer surface of the object. The welded section is provided at least between the first acoustic damper and a second acoustic damper. The welded section secures the second attenuation unit to the first acoustic liner. The communication part is disposed in a position farther from an outer surface of the object than the welded section, allowing communication between the first damper space and a second damper space.

Abstract: An acoustic attenuator comprises a first attenuation unit, a second attenuation unit, a welded section, and a communication part. A first acoustic damper is provided on an outer surface of a first acoustic liner, which faces toward a side opposite from an object, to form a first damper space that communicates with an internal space of the object. The second attenuation unit is attached to an outer surface of the object. The welded section is provided at least between the first acoustic damper and a second acoustic damper. The welded section secures the second attenuation unit to the first acoustic liner. The communication part is disposed in a position farther from an outer surface of the object than the welded section, allowing communication between the first damper space and a second damper space.

Abstract: The present invention is a metal colloid solution comprising: colloidal particles consisting of metal particles consisting of one or two or more metal(s) and a protective agent bonding to the metal particles; and a solvent as a dispersion medium of the colloidal particles, wherein: a chloride ion concentration per a metal concentration of 1 mass % is 25 ppm or less; and a nitrate ion concentration per a metal concentration of 1 mass % is 7500 ppm or less. In the present invention, adsorption performance can be improved with adjustment of the amount of the protective agent of the colloidal particles. It is preferable to bind the protective agent of 0.2 to 2.5 times the mass of the metal particles.

Abstract: The present invention is a metal colloid solution comprising: colloidal particles consisting of metal particles consisting of one or two or more metal(s) and a protective agent bonding to the metal particles; and a solvent as a dispersion medium of the colloidal particles, wherein: a chloride ion concentration per a metal concentration of 1 mass % is 25 ppm or less; and a nitrate ion concentration per a metal concentration of 1 mass % is 7500 ppm or less. In the present invention, adsorption performance can be improved with adjustment of the amount of the protective agent of the colloidal particles. It is preferable to bind the protective agent of 0.2 to 2.5 times the mass of the metal particles.