Optimally graded porous material for broadband perfect absorption of sound

Sound Absorption of Porous Material in Combination with Perforated Facings

The absorption characteristics of porous absorbers in combination with perforated facings was investigated. The effect of the hole size, hole pattern and open area ratio were examined. The absorption coefficients for an absorber of uniform cross-section were compared to those for an absorber with a tapered cross-section for various volumes of absorbent and different perforated facings.

A broadband passive–active sound absorption system

In recent years, hybrid absorption systems have been implemented which achieve high sound absorption over a broad frequency range. This work is an experimental study of a broadband hybrid absorption system which is comprised of a layer of sound-absorbing material ~the passive component! positioned at a distance from a movable wall ~the active component! inside an impedance tube. The movable wal...

Sound propagation in and low frequency noise absorption by helium-filled porous material.

Low-frequency noise is difficult to deal with by traditional porous material due to its inherent high acoustic impedance. This study seeks to extend the effective range of sound absorption to lower frequencies by filling a low density gas, such as helium, in the porous material. Compared with conventional air-filled absorption material, the helium-filled porous material has a much reduced chara...

Title Sound propagation in and low frequency noise absorption byhelium - filled porous material

Broadband Epsilon-Near-Zero Perfect Absorption in the Near-Infrared

Perfect absorption (PA) of incident light is important for both fundamental light-matter interaction studies and practical device applications. PA studies so far have mainly used resonant nanostructures that require delicate structural patterning. Here, we realize tunable and broadband PA in the near-infrared region using relatively simple thin film coatings. We adjust the growth condition of a...