An acoustic structure includes a plate and at least one acoustic scatterer having a resonant frequency and coupled to a side of the plate. The at least one acoustic scatterer has an opening, a first channel and a second channel. The first channel has a first channel open end and a first channel terminal end with the first channel open end being in fluid communication with the opening. The second channel has a second channel open end and a second channel terminal end with the second channel open end being in fluid communication with the opening. The first channel terminal end and the second channel terminal end are separate from one another.

A sound insulation device contains at least one rigid support element and at least one elastic membrane element. The rigid support element contains at least one support grid containing a plurality of cells. The elastic membrane element is arranged on the support grid. The sound insulation device is configured to block at least partially acoustic energy transmission at a frequency range of 60 Hz to 500 Hz. The sound insulation device exhibits a negative effective mass below a resonance frequency, where the resonance frequency is given by:

[00001]${\omega }_0=\frac{4\pi \delta }{A}\sqrt{\frac{E}{\rho \left(1-{\vartheta }^2\right)}},$

where A is a pore size of the support grid spun by the membrane element, δ is a thickness of the membrane element, E is an elastic modulus of the membrane element, ρ is a density of the membrane element, and ϑ is a Poisson ratio of the membrane element. The elastic modulus E of the membrane element is ≥8 MPa.

A sound insulation device contains at least one rigid support element and at least one elastic membrane element. The rigid support element contains at least one support grid containing a plurality of cells. The elastic membrane element is arranged on the support grid. The sound insulation device is configured to block at least partially acoustic energy transmission at a frequency range of 60 Hz to 500 Hz. The sound insulation device exhibits a negative effective mass below a resonance frequency, where the resonance frequency is given by:

[00001]${\omega }_0=\frac{4\pi \delta }{A}\sqrt{\frac{E}{\rho \left(1-{\vartheta }^2\right)}},$

where A is a pore size of the support grid spun by the membrane element, δ is a thickness of the membrane element, E is an elastic modulus of the membrane element, ρ is a density of the membrane element, and ϑ is a Poisson ratio of the membrane element. The elastic modulus E of the membrane element is ≥8 MPa.

A silencer module for an air handling unit includes a first baffle and a second baffle spaced apart from the first baffle to form an air channel between the first baffle and the second baffle. The air channel is configured to receive a fluid flow and direct the fluid flow through the silencer module. The silencer module also includes a reactive acoustic feature formed in the first baffle. The reactive acoustic feature includes an attenuation profile configured to reduce propagation of tonal acoustic waves through the air channel.

A silencer module for an air handling unit includes a first baffle and a second baffle spaced apart from the first baffle to form an air channel between the first baffle and the second baffle. The air channel is configured to receive a fluid flow and direct the fluid flow through the silencer module. The silencer module also includes a reactive acoustic feature formed in the first baffle. The reactive acoustic feature includes an attenuation profile configured to reduce propagation of tonal acoustic waves through the air channel.

A soundproofing material including a porous body having a cell structure and including inorganic fibers other than asbestos, wherein an average cell diameter is more than 300 μm and 1000 μm or less, a bulk density is 0.007 to 0.024 g/cm.sup.3, and a flow resistivity is 170,000 to 2,000,000 Ns/m.sup.4.

A soundproofing material including a porous body having a cell structure and including inorganic fibers other than asbestos, wherein an average cell diameter is more than 300 μm and 1000 μm or less, a bulk density is 0.007 to 0.024 g/cm.sup.3, and a flow resistivity is 170,000 to 2,000,000 Ns/m.sup.4.

Provided is a silencing tubular structure body that has high strength and can be disposed in a narrow space. A tubular member including a tubular portion having a tubular shape, and a frame portion having at least a part formed integrally with an inner peripheral surface side of the tubular portion; and a lid member that is exchangeably disposed on an opening surface of the frame portion of the tubular member are included, in which the frame portion and the lid member form a resonant silencing structure.

Provided is a silencing tubular structure body that has high strength and can be disposed in a narrow space. A tubular member including a tubular portion having a tubular shape, and a frame portion having at least a part formed integrally with an inner peripheral surface side of the tubular portion; and a lid member that is exchangeably disposed on an opening surface of the frame portion of the tubular member are included, in which the frame portion and the lid member form a resonant silencing structure.

Embodiments of the present disclosure provide a diffusion muffling device, a diffusion resonance muffling device, a full-frequency diffusion muffling device, a muffling system for a ventilation channel, and a muffling method using the same, which include a plurality of diffusion muffling units disposed in the ventilation extension direction of the ventilation channel, wherein the plurality of diffusion muffling units are arranged in parallel in a direction with a predetermined angle between the direction and the ventilation extension direction of the ventilation channel, and a muffling passage is formed between each two adjacent diffusion muffling units, wherein each of the diffusion muffling units includes at least one diffuser, and each diffuser includes a plurality of convex portions so that sound waves entering the muffling passage are reflected multiple times in the muffling passage by the plurality of convex portions and then sound is attenuated. In the present disclosure, the diffusers are disposed to diffuse and reflect sound waves, so that the sound is attenuated in a long and narrow passage by multiple times of reflections of the sound waves, thereby improving the low-frequency sound muffling performance in the ventilation channel so as to effectively achieve an effect of sound muffling and noise reduction in ventilation.