We report both experimentally and numerically that a low-frequency acoustic absorber is realized by double split-ring resonators backed with rigid wall. This leverages the impedance matching dissipation effect, which arises due to thermal-viscous loss within dual channels. As result, this achieves near-perfect sound absorption (the coefficient α = 0.99) at subwavelength thickness of around λ/23...

Acoustic energy is an often overlooked but increasingly prevalent source of ambient that could be scavenged to power a wide range devices. Piezoelectric materials are used, the tradeoff between acoustic impedance matching and amount ceramic piezoelectric material as active has not previously been investigated. In this work, commercially available 1–3 dice fill composites with various factors (2...

This paper represents design broadband impedance matching circuit for Coupler to improve power transfer efficiency in the broadband power line communication (BPLC) systems. The Butterworth gain function equalizer is used to design broadband matching circuit. A practical PLC Coupler impedance matching circuit is designed, and the characteristics for S11 and S21 of PLC Coupler are enhanced compar...

Noise generated in flow duct propagates extensively through the connected ductwork. Its propagation through the outlets would contribute to indoor acoustic discomfort and results in environmental problem. Silencers with acoustic lining are commonly adopted for noise mitigation in flow duct. Researchers have been devoting many numerical efforts in assessing the performance of a liner design. In ...

A damping device, consisting of an annular tail-pipe, has been developed. It is applicable in situations wherein acoustic damping is required in combination with low flow resistance. Examples are ventilation systems, turbo-engines, intake and exhaust systems for internal combustion engines. The device consists of a central tube surrounded by a narrow slit. The central tube has an acoustic mass ...

We describe a simple and inexpensive method for monitoring nasal air flow resistance using measurement of the small-signal acoustic input impedance of the nasal passage, similar to the audiological measurement of ear drum compliance with acoustic tympanometry. The method requires generation of a fixed sinusoidal volume-velocity stimulus using ear-bud speakers, and an electret microphone to moni...

Headphones and earphones have many extremely small holes or narrow slits; they use sound-absorbing or porous material (i.e., dampers) to suppress vibratory system resonance. The air viscosity in these acoustic paths greatly affects the acoustic properties. Simulation analyses such as the finite element method (FEM) therefore require knowledge of the material properties of sound-absorbing or por...